unit_graph.cc 53.1 KB
Newer Older
1
2
/*!
 *  Copyright (c) 2019 by Contributors
Minjie Wang's avatar
Minjie Wang committed
3
4
 * \file graph/unit_graph.cc
 * \brief UnitGraph graph implementation
5
6
 */
#include <dgl/array.h>
7
#include <dgl/base_heterograph.h>
8
9
#include <dgl/immutable_graph.h>
#include <dgl/lazy.h>
10
11

#include "../c_api_common.h"
12
#include "./unit_graph.h"
13
14

namespace dgl {
15

16
namespace {
17
18
19

using namespace dgl::aten;

Minjie Wang's avatar
Minjie Wang committed
20
21
22
23
24
25
26
27
28
29
// create metagraph of one node type
inline GraphPtr CreateUnitGraphMetaGraph1() {
  // a self-loop edge 0->0
  std::vector<int64_t> row_vec(1, 0);
  std::vector<int64_t> col_vec(1, 0);
  IdArray row = aten::VecToIdArray(row_vec);
  IdArray col = aten::VecToIdArray(col_vec);
  GraphPtr g = ImmutableGraph::CreateFromCOO(1, row, col);
  return g;
}
30

Minjie Wang's avatar
Minjie Wang committed
31
32
33
34
35
// create metagraph of two node types
inline GraphPtr CreateUnitGraphMetaGraph2() {
  // an edge 0->1
  std::vector<int64_t> row_vec(1, 0);
  std::vector<int64_t> col_vec(1, 1);
36
37
38
39
40
  IdArray row = aten::VecToIdArray(row_vec);
  IdArray col = aten::VecToIdArray(col_vec);
  GraphPtr g = ImmutableGraph::CreateFromCOO(2, row, col);
  return g;
}
Minjie Wang's avatar
Minjie Wang committed
41
42
43
44
45
46
47
48
49
50
51
52

inline GraphPtr CreateUnitGraphMetaGraph(int num_vtypes) {
  static GraphPtr mg1 = CreateUnitGraphMetaGraph1();
  static GraphPtr mg2 = CreateUnitGraphMetaGraph2();
  if (num_vtypes == 1)
    return mg1;
  else if (num_vtypes == 2)
    return mg2;
  else
    LOG(FATAL) << "Invalid number of vertex types. Must be 1 or 2.";
  return {};
}
53
54

};  // namespace
55
56
57
58
59
60
61

//////////////////////////////////////////////////////////
//
// COO graph implementation
//
//////////////////////////////////////////////////////////

Minjie Wang's avatar
Minjie Wang committed
62
class UnitGraph::COO : public BaseHeteroGraph {
63
 public:
Minjie Wang's avatar
Minjie Wang committed
64
65
  COO(GraphPtr metagraph, int64_t num_src, int64_t num_dst, IdArray src, IdArray dst)
    : BaseHeteroGraph(metagraph) {
66
67
68
    CHECK(aten::IsValidIdArray(src));
    CHECK(aten::IsValidIdArray(dst));
    CHECK_EQ(src->shape[0], dst->shape[0]) << "Input arrays should have the same length.";
69
70
    adj_ = aten::COOMatrix{num_src, num_dst, src, dst};
  }
71

72
73
74
75
  COO(GraphPtr metagraph, const aten::COOMatrix& coo)
    : BaseHeteroGraph(metagraph), adj_(coo) {
    // Data index should not be inherited. Edges in COO format are always
    // assigned ids from 0 to num_edges - 1.
76
    CHECK(!COOHasData(coo)) << "[BUG] COO should not contain data.";
77
    adj_.data = aten::NullArray();
78
  }
79

80
81
82
83
84
85
86
87
88
89
90
  COO() {
    // set magic num_rows/num_cols to mark it as undefined
    // adj_.num_rows == 0 and adj_.num_cols == 0 means empty UnitGraph which is supported
    adj_.num_rows = -1;
    adj_.num_cols = -1;
  };

  bool defined() const {
    return (adj_.num_rows >= 0) && (adj_.num_cols >= 0);
  }

Minjie Wang's avatar
Minjie Wang committed
91
92
  inline dgl_type_t SrcType() const {
    return 0;
93
  }
Minjie Wang's avatar
Minjie Wang committed
94
95
96
97
98
99
100

  inline dgl_type_t DstType() const {
    return NumVertexTypes() == 1? 0 : 1;
  }

  inline dgl_type_t EdgeType() const {
    return 0;
101
102
103
  }

  HeteroGraphPtr GetRelationGraph(dgl_type_t etype) const override {
Minjie Wang's avatar
Minjie Wang committed
104
    LOG(FATAL) << "The method shouldn't be called for UnitGraph graph. "
105
106
107
108
109
      << "The relation graph is simply this graph itself.";
    return {};
  }

  void AddVertices(dgl_type_t vtype, uint64_t num_vertices) override {
Minjie Wang's avatar
Minjie Wang committed
110
    LOG(FATAL) << "UnitGraph graph is not mutable.";
111
112
113
  }

  void AddEdge(dgl_type_t etype, dgl_id_t src, dgl_id_t dst) override {
Minjie Wang's avatar
Minjie Wang committed
114
    LOG(FATAL) << "UnitGraph graph is not mutable.";
115
116
117
  }

  void AddEdges(dgl_type_t etype, IdArray src_ids, IdArray dst_ids) override {
Minjie Wang's avatar
Minjie Wang committed
118
    LOG(FATAL) << "UnitGraph graph is not mutable.";
119
120
121
  }

  void Clear() override {
Minjie Wang's avatar
Minjie Wang committed
122
    LOG(FATAL) << "UnitGraph graph is not mutable.";
123
124
  }

125
126
127
128
  DLDataType DataType() const override {
    return adj_.row->dtype;
  }

129
130
131
132
133
134
135
136
  DLContext Context() const override {
    return adj_.row->ctx;
  }

  uint8_t NumBits() const override {
    return adj_.row->dtype.bits;
  }

137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
  COO AsNumBits(uint8_t bits) const {
    if (NumBits() == bits)
      return *this;

    COO ret(
        meta_graph_,
        adj_.num_rows, adj_.num_cols,
        aten::AsNumBits(adj_.row, bits),
        aten::AsNumBits(adj_.col, bits));
    return ret;
  }

  COO CopyTo(const DLContext& ctx) const {
    if (Context() == ctx)
      return *this;
152
    return COO(meta_graph_, adj_.CopyTo(ctx));
153
154
  }

155
  bool IsMultigraph() const override {
156
    return aten::COOHasDuplicate(adj_);
157
158
159
160
161
162
163
  }

  bool IsReadonly() const override {
    return true;
  }

  uint64_t NumVertices(dgl_type_t vtype) const override {
Minjie Wang's avatar
Minjie Wang committed
164
    if (vtype == SrcType()) {
165
      return adj_.num_rows;
Minjie Wang's avatar
Minjie Wang committed
166
    } else if (vtype == DstType()) {
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
      return adj_.num_cols;
    } else {
      LOG(FATAL) << "Invalid vertex type: " << vtype;
      return 0;
    }
  }

  uint64_t NumEdges(dgl_type_t etype) const override {
    return adj_.row->shape[0];
  }

  bool HasVertex(dgl_type_t vtype, dgl_id_t vid) const override {
    return vid < NumVertices(vtype);
  }

  BoolArray HasVertices(dgl_type_t vtype, IdArray vids) const override {
    LOG(FATAL) << "Not enabled for COO graph";
    return {};
  }

  bool HasEdgeBetween(dgl_type_t etype, dgl_id_t src, dgl_id_t dst) const override {
188
189
190
    CHECK(HasVertex(SrcType(), src)) << "Invalid src vertex id: " << src;
    CHECK(HasVertex(DstType(), dst)) << "Invalid dst vertex id: " << dst;
    return aten::COOIsNonZero(adj_, src, dst);
191
192
193
  }

  BoolArray HasEdgesBetween(dgl_type_t etype, IdArray src_ids, IdArray dst_ids) const override {
194
195
196
    CHECK(aten::IsValidIdArray(src_ids)) << "Invalid vertex id array.";
    CHECK(aten::IsValidIdArray(dst_ids)) << "Invalid vertex id array.";
    return aten::COOIsNonZero(adj_, src_ids, dst_ids);
197
198
199
  }

  IdArray Predecessors(dgl_type_t etype, dgl_id_t dst) const override {
200
201
    CHECK(HasVertex(DstType(), dst)) << "Invalid dst vertex id: " << dst;
    return aten::COOGetRowDataAndIndices(aten::COOTranspose(adj_), dst).second;
202
203
204
  }

  IdArray Successors(dgl_type_t etype, dgl_id_t src) const override {
205
206
    CHECK(HasVertex(SrcType(), src)) << "Invalid src vertex id: " << src;
    return aten::COOGetRowDataAndIndices(adj_, src).second;
207
208
209
  }

  IdArray EdgeId(dgl_type_t etype, dgl_id_t src, dgl_id_t dst) const override {
210
211
    CHECK(HasVertex(SrcType(), src)) << "Invalid src vertex id: " << src;
    CHECK(HasVertex(DstType(), dst)) << "Invalid dst vertex id: " << dst;
212
    return aten::COOGetAllData(adj_, src, dst);
213
214
  }

215
  EdgeArray EdgeIdsAll(dgl_type_t etype, IdArray src, IdArray dst) const override {
216
217
218
219
    CHECK(aten::IsValidIdArray(src)) << "Invalid vertex id array.";
    CHECK(aten::IsValidIdArray(dst)) << "Invalid vertex id array.";
    const auto& arrs = aten::COOGetDataAndIndices(adj_, src, dst);
    return EdgeArray{arrs[0], arrs[1], arrs[2]};
220
221
  }

222
223
224
225
  IdArray EdgeIdsOne(dgl_type_t etype, IdArray src, IdArray dst) const override {
    return aten::COOGetData(adj_, src, dst);
  }

226
227
  std::pair<dgl_id_t, dgl_id_t> FindEdge(dgl_type_t etype, dgl_id_t eid) const override {
    CHECK(eid < NumEdges(etype)) << "Invalid edge id: " << eid;
228
229
    const dgl_id_t src = aten::IndexSelect<int64_t>(adj_.row, eid);
    const dgl_id_t dst = aten::IndexSelect<int64_t>(adj_.col, eid);
230
231
232
233
    return std::pair<dgl_id_t, dgl_id_t>(src, dst);
  }

  EdgeArray FindEdges(dgl_type_t etype, IdArray eids) const override {
234
    CHECK(aten::IsValidIdArray(eids)) << "Invalid edge id array";
235
236
    BUG_ON(aten::IsNullArray(adj_.data)) <<
      "FindEdges requires the internal COO matrix not having EIDs.";
237
238
239
240
241
242
    return EdgeArray{aten::IndexSelect(adj_.row, eids),
                     aten::IndexSelect(adj_.col, eids),
                     eids};
  }

  EdgeArray InEdges(dgl_type_t etype, dgl_id_t vid) const override {
243
244
245
246
247
    IdArray ret_src, ret_eid;
    std::tie(ret_eid, ret_src) = aten::COOGetRowDataAndIndices(
        aten::COOTranspose(adj_), vid);
    IdArray ret_dst = aten::Full(vid, ret_src->shape[0], NumBits(), ret_src->ctx);
    return EdgeArray{ret_src, ret_dst, ret_eid};
248
249
250
  }

  EdgeArray InEdges(dgl_type_t etype, IdArray vids) const override {
251
252
253
254
    CHECK(aten::IsValidIdArray(vids)) << "Invalid vertex id array.";
    auto coosubmat = aten::COOSliceRows(aten::COOTranspose(adj_), vids);
    auto row = aten::IndexSelect(vids, coosubmat.row);
    return EdgeArray{coosubmat.col, row, coosubmat.data};
255
256
257
  }

  EdgeArray OutEdges(dgl_type_t etype, dgl_id_t vid) const override {
258
259
260
261
    IdArray ret_dst, ret_eid;
    std::tie(ret_eid, ret_dst) = aten::COOGetRowDataAndIndices(adj_, vid);
    IdArray ret_src = aten::Full(vid, ret_dst->shape[0], NumBits(), ret_dst->ctx);
    return EdgeArray{ret_src, ret_dst, ret_eid};
262
263
264
  }

  EdgeArray OutEdges(dgl_type_t etype, IdArray vids) const override {
265
266
267
268
    CHECK(aten::IsValidIdArray(vids)) << "Invalid vertex id array.";
    auto coosubmat = aten::COOSliceRows(adj_, vids);
    auto row = aten::IndexSelect(vids, coosubmat.row);
    return EdgeArray{row, coosubmat.col, coosubmat.data};
269
270
271
272
273
274
275
276
277
278
279
  }

  EdgeArray Edges(dgl_type_t etype, const std::string &order = "") const override {
    CHECK(order.empty() || order == std::string("eid"))
      << "COO only support Edges of order \"eid\", but got \""
      << order << "\".";
    IdArray rst_eid = aten::Range(0, NumEdges(etype), NumBits(), Context());
    return EdgeArray{adj_.row, adj_.col, rst_eid};
  }

  uint64_t InDegree(dgl_type_t etype, dgl_id_t vid) const override {
280
281
    CHECK(HasVertex(DstType(), vid)) << "Invalid dst vertex id: " << vid;
    return aten::COOGetRowNNZ(aten::COOTranspose(adj_), vid);
282
283
284
  }

  DegreeArray InDegrees(dgl_type_t etype, IdArray vids) const override {
285
286
    CHECK(aten::IsValidIdArray(vids)) << "Invalid vertex id array.";
    return aten::COOGetRowNNZ(aten::COOTranspose(adj_), vids);
287
288
289
  }

  uint64_t OutDegree(dgl_type_t etype, dgl_id_t vid) const override {
290
291
    CHECK(HasVertex(SrcType(), vid)) << "Invalid src vertex id: " << vid;
    return aten::COOGetRowNNZ(adj_, vid);
292
293
294
  }

  DegreeArray OutDegrees(dgl_type_t etype, IdArray vids) const override {
295
296
    CHECK(aten::IsValidIdArray(vids)) << "Invalid vertex id array.";
    return aten::COOGetRowNNZ(adj_, vids);
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
  }

  DGLIdIters SuccVec(dgl_type_t etype, dgl_id_t vid) const override {
    LOG(INFO) << "Not enabled for COO graph.";
    return {};
  }

  DGLIdIters OutEdgeVec(dgl_type_t etype, dgl_id_t vid) const override {
    LOG(INFO) << "Not enabled for COO graph.";
    return {};
  }

  DGLIdIters PredVec(dgl_type_t etype, dgl_id_t vid) const override {
    LOG(INFO) << "Not enabled for COO graph.";
    return {};
  }

  DGLIdIters InEdgeVec(dgl_type_t etype, dgl_id_t vid) const override {
    LOG(INFO) << "Not enabled for COO graph.";
    return {};
  }

  std::vector<IdArray> GetAdj(
      dgl_type_t etype, bool transpose, const std::string &fmt) const override {
    CHECK(fmt == "coo") << "Not valid adj format request.";
    if (transpose) {
      return {aten::HStack(adj_.col, adj_.row)};
    } else {
      return {aten::HStack(adj_.row, adj_.col)};
    }
  }

329
330
331
332
333
334
335
336
337
338
339
340
341
342
  aten::COOMatrix GetCOOMatrix(dgl_type_t etype) const override {
    return adj_;
  }

  aten::CSRMatrix GetCSCMatrix(dgl_type_t etype) const override {
    LOG(FATAL) << "Not enabled for COO graph";
    return aten::CSRMatrix();
  }

  aten::CSRMatrix GetCSRMatrix(dgl_type_t etype) const override {
    LOG(FATAL) << "Not enabled for COO graph";
    return aten::CSRMatrix();
  }

343
  SparseFormat SelectFormat(dgl_type_t etype, dgl_format_code_t preferred_formats) const override {
344
    LOG(FATAL) << "Not enabled for COO graph";
345
    return SparseFormat::kCOO;
346
347
  }

348
  dgl_format_code_t GetAllowedFormats() const override {
349
    LOG(FATAL) << "Not enabled for COO graph";
350
    return 0;
351
352
  }

353
  dgl_format_code_t GetCreatedFormats() const override {
354
355
356
357
    LOG(FATAL) << "Not enabled for COO graph";
    return 0;
  }

358
  HeteroSubgraph VertexSubgraph(const std::vector<IdArray>& vids) const override {
359
360
361
362
363
364
365
366
367
368
369
370
    CHECK_EQ(vids.size(), NumVertexTypes()) << "Number of vertex types mismatch";
    auto srcvids = vids[SrcType()], dstvids = vids[DstType()];
    CHECK(aten::IsValidIdArray(srcvids)) << "Invalid vertex id array.";
    CHECK(aten::IsValidIdArray(dstvids)) << "Invalid vertex id array.";
    HeteroSubgraph subg;
    const auto& submat = aten::COOSliceMatrix(adj_, srcvids, dstvids);
    IdArray sub_eids = aten::Range(0, submat.data->shape[0], NumBits(), Context());
    subg.graph = std::make_shared<COO>(meta_graph(), submat.num_rows, submat.num_cols,
        submat.row, submat.col);
    subg.induced_vertices = vids;
    subg.induced_edges.emplace_back(submat.data);
    return subg;
371
372
373
374
375
376
377
378
379
380
381
382
383
384
  }

  HeteroSubgraph EdgeSubgraph(
      const std::vector<IdArray>& eids, bool preserve_nodes = false) const override {
    CHECK_EQ(eids.size(), 1) << "Edge type number mismatch.";
    HeteroSubgraph subg;
    if (!preserve_nodes) {
      IdArray new_src = aten::IndexSelect(adj_.row, eids[0]);
      IdArray new_dst = aten::IndexSelect(adj_.col, eids[0]);
      subg.induced_vertices.emplace_back(aten::Relabel_({new_src}));
      subg.induced_vertices.emplace_back(aten::Relabel_({new_dst}));
      const auto new_nsrc = subg.induced_vertices[0]->shape[0];
      const auto new_ndst = subg.induced_vertices[1]->shape[0];
      subg.graph = std::make_shared<COO>(
Minjie Wang's avatar
Minjie Wang committed
385
          meta_graph(), new_nsrc, new_ndst, new_src, new_dst);
386
387
388
389
      subg.induced_edges = eids;
    } else {
      IdArray new_src = aten::IndexSelect(adj_.row, eids[0]);
      IdArray new_dst = aten::IndexSelect(adj_.col, eids[0]);
Quan (Andy) Gan's avatar
Quan (Andy) Gan committed
390
391
392
393
      subg.induced_vertices.emplace_back(
          aten::Range(0, NumVertices(SrcType()), NumBits(), Context()));
      subg.induced_vertices.emplace_back(
          aten::Range(0, NumVertices(DstType()), NumBits(), Context()));
394
      subg.graph = std::make_shared<COO>(
Quan (Andy) Gan's avatar
Quan (Andy) Gan committed
395
          meta_graph(), NumVertices(SrcType()), NumVertices(DstType()), new_src, new_dst);
396
397
398
399
400
      subg.induced_edges = eids;
    }
    return subg;
  }

401
  HeteroGraphPtr GetGraphInFormat(dgl_format_code_t formats) const override {
402
403
404
405
    LOG(FATAL) << "Not enabled for COO graph.";
    return nullptr;
  }

406
407
408
409
  aten::COOMatrix adj() const {
    return adj_;
  }

410
411
412
413
414
415
416
417
418
  /*!
   * \brief Determines whether the graph is "hypersparse", i.e. having significantly more
   * nodes than edges.
   */
  bool IsHypersparse() const {
    return (NumVertices(SrcType()) / 8 > NumEdges(EdgeType())) &&
           (NumVertices(SrcType()) > 1000000);
  }

419
420
421
422
423
424
425
426
427
428
429
430
431
  bool Load(dmlc::Stream* fs) {
    auto meta_imgraph = Serializer::make_shared<ImmutableGraph>();
    CHECK(fs->Read(&meta_imgraph)) << "Invalid meta graph";
    meta_graph_ = meta_imgraph;
    CHECK(fs->Read(&adj_)) << "Invalid adj matrix";
    return true;
  }
  void Save(dmlc::Stream* fs) const {
    auto meta_graph_ptr = ImmutableGraph::ToImmutable(meta_graph());
    fs->Write(meta_graph_ptr);
    fs->Write(adj_);
  }

432
 private:
433
434
  friend class Serializer;

435
436
437
438
439
440
441
442
443
444
445
  /*! \brief internal adjacency matrix. Data array is empty */
  aten::COOMatrix adj_;
};

//////////////////////////////////////////////////////////
//
// CSR graph implementation
//
//////////////////////////////////////////////////////////

/*! \brief CSR graph */
Minjie Wang's avatar
Minjie Wang committed
446
class UnitGraph::CSR : public BaseHeteroGraph {
447
 public:
Minjie Wang's avatar
Minjie Wang committed
448
  CSR(GraphPtr metagraph, int64_t num_src, int64_t num_dst,
449
      IdArray indptr, IdArray indices, IdArray edge_ids)
Minjie Wang's avatar
Minjie Wang committed
450
    : BaseHeteroGraph(metagraph) {
451
452
453
454
455
    CHECK(aten::IsValidIdArray(indptr));
    CHECK(aten::IsValidIdArray(indices));
    CHECK(aten::IsValidIdArray(edge_ids));
    CHECK_EQ(indices->shape[0], edge_ids->shape[0])
      << "indices and edge id arrays should have the same length";
456

457
458
459
    adj_ = aten::CSRMatrix{num_src, num_dst, indptr, indices, edge_ids};
  }

460
  CSR(GraphPtr metagraph, const aten::CSRMatrix& csr)
Da Zheng's avatar
Da Zheng committed
461
462
    : BaseHeteroGraph(metagraph), adj_(csr) {
  }
463

464
465
466
467
468
469
470
471
472
473
474
  CSR() {
    // set magic num_rows/num_cols to mark it as undefined
    // adj_.num_rows == 0 and adj_.num_cols == 0 means empty UnitGraph which is supported
    adj_.num_rows = -1;
    adj_.num_cols = -1;
  };

  bool defined() const {
    return (adj_.num_rows >= 0) || (adj_.num_cols >= 0);
  }

Minjie Wang's avatar
Minjie Wang committed
475
476
  inline dgl_type_t SrcType() const {
    return 0;
477
  }
Minjie Wang's avatar
Minjie Wang committed
478
479
480
481
482
483
484

  inline dgl_type_t DstType() const {
    return NumVertexTypes() == 1? 0 : 1;
  }

  inline dgl_type_t EdgeType() const {
    return 0;
485
486
487
  }

  HeteroGraphPtr GetRelationGraph(dgl_type_t etype) const override {
Minjie Wang's avatar
Minjie Wang committed
488
    LOG(FATAL) << "The method shouldn't be called for UnitGraph graph. "
489
490
491
492
493
      << "The relation graph is simply this graph itself.";
    return {};
  }

  void AddVertices(dgl_type_t vtype, uint64_t num_vertices) override {
Minjie Wang's avatar
Minjie Wang committed
494
    LOG(FATAL) << "UnitGraph graph is not mutable.";
495
496
497
  }

  void AddEdge(dgl_type_t etype, dgl_id_t src, dgl_id_t dst) override {
Minjie Wang's avatar
Minjie Wang committed
498
    LOG(FATAL) << "UnitGraph graph is not mutable.";
499
500
501
  }

  void AddEdges(dgl_type_t etype, IdArray src_ids, IdArray dst_ids) override {
Minjie Wang's avatar
Minjie Wang committed
502
    LOG(FATAL) << "UnitGraph graph is not mutable.";
503
504
505
  }

  void Clear() override {
Minjie Wang's avatar
Minjie Wang committed
506
    LOG(FATAL) << "UnitGraph graph is not mutable.";
507
508
  }

509
510
511
512
  DLDataType DataType() const override {
    return adj_.indices->dtype;
  }

513
514
515
516
517
518
519
520
  DLContext Context() const override {
    return adj_.indices->ctx;
  }

  uint8_t NumBits() const override {
    return adj_.indices->dtype.bits;
  }

521
522
523
524
525
  CSR AsNumBits(uint8_t bits) const {
    if (NumBits() == bits) {
      return *this;
    } else {
      CSR ret(
Minjie Wang's avatar
Minjie Wang committed
526
          meta_graph_,
527
528
529
530
531
532
533
534
535
536
537
538
          adj_.num_rows, adj_.num_cols,
          aten::AsNumBits(adj_.indptr, bits),
          aten::AsNumBits(adj_.indices, bits),
          aten::AsNumBits(adj_.data, bits));
      return ret;
    }
  }

  CSR CopyTo(const DLContext& ctx) const {
    if (Context() == ctx) {
      return *this;
    } else {
539
      return CSR(meta_graph_, adj_.CopyTo(ctx));
540
541
542
    }
  }

543
  bool IsMultigraph() const override {
544
    return aten::CSRHasDuplicate(adj_);
545
546
547
548
549
550
551
  }

  bool IsReadonly() const override {
    return true;
  }

  uint64_t NumVertices(dgl_type_t vtype) const override {
Minjie Wang's avatar
Minjie Wang committed
552
    if (vtype == SrcType()) {
553
      return adj_.num_rows;
Minjie Wang's avatar
Minjie Wang committed
554
    } else if (vtype == DstType()) {
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
      return adj_.num_cols;
    } else {
      LOG(FATAL) << "Invalid vertex type: " << vtype;
      return 0;
    }
  }

  uint64_t NumEdges(dgl_type_t etype) const override {
    return adj_.indices->shape[0];
  }

  bool HasVertex(dgl_type_t vtype, dgl_id_t vid) const override {
    return vid < NumVertices(vtype);
  }

  BoolArray HasVertices(dgl_type_t vtype, IdArray vids) const override {
    LOG(FATAL) << "Not enabled for COO graph";
    return {};
  }

  bool HasEdgeBetween(dgl_type_t etype, dgl_id_t src, dgl_id_t dst) const override {
Minjie Wang's avatar
Minjie Wang committed
576
577
    CHECK(HasVertex(SrcType(), src)) << "Invalid src vertex id: " << src;
    CHECK(HasVertex(DstType(), dst)) << "Invalid dst vertex id: " << dst;
578
579
580
581
    return aten::CSRIsNonZero(adj_, src, dst);
  }

  BoolArray HasEdgesBetween(dgl_type_t etype, IdArray src_ids, IdArray dst_ids) const override {
582
583
    CHECK(aten::IsValidIdArray(src_ids)) << "Invalid vertex id array.";
    CHECK(aten::IsValidIdArray(dst_ids)) << "Invalid vertex id array.";
584
585
586
587
588
589
590
591
592
    return aten::CSRIsNonZero(adj_, src_ids, dst_ids);
  }

  IdArray Predecessors(dgl_type_t etype, dgl_id_t dst) const override {
    LOG(INFO) << "Not enabled for CSR graph.";
    return {};
  }

  IdArray Successors(dgl_type_t etype, dgl_id_t src) const override {
Minjie Wang's avatar
Minjie Wang committed
593
    CHECK(HasVertex(SrcType(), src)) << "Invalid src vertex id: " << src;
594
595
596
597
    return aten::CSRGetRowColumnIndices(adj_, src);
  }

  IdArray EdgeId(dgl_type_t etype, dgl_id_t src, dgl_id_t dst) const override {
Minjie Wang's avatar
Minjie Wang committed
598
599
    CHECK(HasVertex(SrcType(), src)) << "Invalid src vertex id: " << src;
    CHECK(HasVertex(DstType(), dst)) << "Invalid dst vertex id: " << dst;
600
    return aten::CSRGetAllData(adj_, src, dst);
601
602
  }

603
  EdgeArray EdgeIdsAll(dgl_type_t etype, IdArray src, IdArray dst) const override {
604
605
    CHECK(aten::IsValidIdArray(src)) << "Invalid vertex id array.";
    CHECK(aten::IsValidIdArray(dst)) << "Invalid vertex id array.";
606
607
608
609
    const auto& arrs = aten::CSRGetDataAndIndices(adj_, src, dst);
    return EdgeArray{arrs[0], arrs[1], arrs[2]};
  }

610
611
612
613
  IdArray EdgeIdsOne(dgl_type_t etype, IdArray src, IdArray dst) const override {
    return aten::CSRGetData(adj_, src, dst);
  }

614
  std::pair<dgl_id_t, dgl_id_t> FindEdge(dgl_type_t etype, dgl_id_t eid) const override {
615
    LOG(FATAL) << "Not enabled for CSR graph.";
616
617
618
619
    return {};
  }

  EdgeArray FindEdges(dgl_type_t etype, IdArray eids) const override {
620
    LOG(FATAL) << "Not enabled for CSR graph.";
621
622
623
624
    return {};
  }

  EdgeArray InEdges(dgl_type_t etype, dgl_id_t vid) const override {
625
    LOG(FATAL) << "Not enabled for CSR graph.";
626
627
628
629
    return {};
  }

  EdgeArray InEdges(dgl_type_t etype, IdArray vids) const override {
630
    LOG(FATAL) << "Not enabled for CSR graph.";
631
632
633
634
    return {};
  }

  EdgeArray OutEdges(dgl_type_t etype, dgl_id_t vid) const override {
Minjie Wang's avatar
Minjie Wang committed
635
    CHECK(HasVertex(SrcType(), vid)) << "Invalid src vertex id: " << vid;
636
637
638
639
640
641
642
    IdArray ret_dst = aten::CSRGetRowColumnIndices(adj_, vid);
    IdArray ret_eid = aten::CSRGetRowData(adj_, vid);
    IdArray ret_src = aten::Full(vid, ret_dst->shape[0], NumBits(), ret_dst->ctx);
    return EdgeArray{ret_src, ret_dst, ret_eid};
  }

  EdgeArray OutEdges(dgl_type_t etype, IdArray vids) const override {
643
    CHECK(aten::IsValidIdArray(vids)) << "Invalid vertex id array.";
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
    auto csrsubmat = aten::CSRSliceRows(adj_, vids);
    auto coosubmat = aten::CSRToCOO(csrsubmat, false);
    // Note that the row id in the csr submat is relabled, so
    // we need to recover it using an index select.
    auto row = aten::IndexSelect(vids, coosubmat.row);
    return EdgeArray{row, coosubmat.col, coosubmat.data};
  }

  EdgeArray Edges(dgl_type_t etype, const std::string &order = "") const override {
    CHECK(order.empty() || order == std::string("srcdst"))
      << "CSR only support Edges of order \"srcdst\","
      << " but got \"" << order << "\".";
    const auto& coo = aten::CSRToCOO(adj_, false);
    return EdgeArray{coo.row, coo.col, coo.data};
  }

  uint64_t InDegree(dgl_type_t etype, dgl_id_t vid) const override {
661
    LOG(FATAL) << "Not enabled for CSR graph.";
662
663
664
665
    return {};
  }

  DegreeArray InDegrees(dgl_type_t etype, IdArray vids) const override {
666
    LOG(FATAL) << "Not enabled for CSR graph.";
667
668
669
670
    return {};
  }

  uint64_t OutDegree(dgl_type_t etype, dgl_id_t vid) const override {
Minjie Wang's avatar
Minjie Wang committed
671
    CHECK(HasVertex(SrcType(), vid)) << "Invalid src vertex id: " << vid;
672
673
674
675
    return aten::CSRGetRowNNZ(adj_, vid);
  }

  DegreeArray OutDegrees(dgl_type_t etype, IdArray vids) const override {
676
    CHECK(aten::IsValidIdArray(vids)) << "Invalid vertex id array.";
677
678
679
680
681
682
    return aten::CSRGetRowNNZ(adj_, vids);
  }

  DGLIdIters SuccVec(dgl_type_t etype, dgl_id_t vid) const override {
    // TODO(minjie): This still assumes the data type and device context
    //   of this graph. Should fix later.
683
    CHECK_EQ(NumBits(), 64);
684
685
686
687
688
689
690
    const dgl_id_t* indptr_data = static_cast<dgl_id_t*>(adj_.indptr->data);
    const dgl_id_t* indices_data = static_cast<dgl_id_t*>(adj_.indices->data);
    const dgl_id_t start = indptr_data[vid];
    const dgl_id_t end = indptr_data[vid + 1];
    return DGLIdIters(indices_data + start, indices_data + end);
  }

691
692
693
694
695
696
697
698
699
700
  DGLIdIters32 SuccVec32(dgl_type_t etype, dgl_id_t vid) {
    // TODO(minjie): This still assumes the data type and device context
    //   of this graph. Should fix later.
    const int32_t* indptr_data = static_cast<int32_t*>(adj_.indptr->data);
    const int32_t* indices_data = static_cast<int32_t*>(adj_.indices->data);
    const int32_t start = indptr_data[vid];
    const int32_t end = indptr_data[vid + 1];
    return DGLIdIters32(indices_data + start, indices_data + end);
  }

701
702
703
  DGLIdIters OutEdgeVec(dgl_type_t etype, dgl_id_t vid) const override {
    // TODO(minjie): This still assumes the data type and device context
    //   of this graph. Should fix later.
704
    CHECK_EQ(NumBits(), 64);
705
706
707
708
709
710
711
712
    const dgl_id_t* indptr_data = static_cast<dgl_id_t*>(adj_.indptr->data);
    const dgl_id_t* eid_data = static_cast<dgl_id_t*>(adj_.data->data);
    const dgl_id_t start = indptr_data[vid];
    const dgl_id_t end = indptr_data[vid + 1];
    return DGLIdIters(eid_data + start, eid_data + end);
  }

  DGLIdIters PredVec(dgl_type_t etype, dgl_id_t vid) const override {
713
    LOG(FATAL) << "Not enabled for CSR graph.";
714
715
716
717
    return {};
  }

  DGLIdIters InEdgeVec(dgl_type_t etype, dgl_id_t vid) const override {
718
    LOG(FATAL) << "Not enabled for CSR graph.";
719
720
721
722
723
724
725
726
727
    return {};
  }

  std::vector<IdArray> GetAdj(
      dgl_type_t etype, bool transpose, const std::string &fmt) const override {
    CHECK(!transpose && fmt == "csr") << "Not valid adj format request.";
    return {adj_.indptr, adj_.indices, adj_.data};
  }

728
729
730
731
732
733
734
735
736
737
738
739
740
741
  aten::COOMatrix GetCOOMatrix(dgl_type_t etype) const override {
    LOG(FATAL) << "Not enabled for CSR graph";
    return aten::COOMatrix();
  }

  aten::CSRMatrix GetCSCMatrix(dgl_type_t etype) const override {
    LOG(FATAL) << "Not enabled for CSR graph";
    return aten::CSRMatrix();
  }

  aten::CSRMatrix GetCSRMatrix(dgl_type_t etype) const override {
    return adj_;
  }

742
  SparseFormat SelectFormat(dgl_type_t etype, dgl_format_code_t preferred_formats) const override {
743
    LOG(FATAL) << "Not enabled for CSR graph";
744
    return SparseFormat::kCSR;
745
746
  }

747
748
749
  dgl_format_code_t GetAllowedFormats() const override {
    LOG(FATAL) << "Not enabled for COO graph";
    return 0;
750
751
  }

752
  dgl_format_code_t GetCreatedFormats() const override {
753
754
755
756
    LOG(FATAL) << "Not enabled for CSR graph";
    return 0;
  }

757
  HeteroSubgraph VertexSubgraph(const std::vector<IdArray>& vids) const override {
Minjie Wang's avatar
Minjie Wang committed
758
759
760
761
    CHECK_EQ(vids.size(), NumVertexTypes()) << "Number of vertex types mismatch";
    auto srcvids = vids[SrcType()], dstvids = vids[DstType()];
    CHECK(aten::IsValidIdArray(srcvids)) << "Invalid vertex id array.";
    CHECK(aten::IsValidIdArray(dstvids)) << "Invalid vertex id array.";
762
    HeteroSubgraph subg;
Minjie Wang's avatar
Minjie Wang committed
763
    const auto& submat = aten::CSRSliceMatrix(adj_, srcvids, dstvids);
764
    IdArray sub_eids = aten::Range(0, submat.data->shape[0], NumBits(), Context());
Minjie Wang's avatar
Minjie Wang committed
765
    subg.graph = std::make_shared<CSR>(meta_graph(), submat.num_rows, submat.num_cols,
766
767
768
769
770
771
772
773
        submat.indptr, submat.indices, sub_eids);
    subg.induced_vertices = vids;
    subg.induced_edges.emplace_back(submat.data);
    return subg;
  }

  HeteroSubgraph EdgeSubgraph(
      const std::vector<IdArray>& eids, bool preserve_nodes = false) const override {
774
    LOG(FATAL) << "Not enabled for CSR graph.";
775
776
777
    return {};
  }

778
  HeteroGraphPtr GetGraphInFormat(dgl_format_code_t formats) const override {
779
780
781
782
    LOG(FATAL) << "Not enabled for CSR graph.";
    return nullptr;
  }

783
784
785
786
  aten::CSRMatrix adj() const {
    return adj_;
  }

787
788
789
790
791
792
793
794
795
796
797
798
799
  bool Load(dmlc::Stream* fs) {
    auto meta_imgraph = Serializer::make_shared<ImmutableGraph>();
    CHECK(fs->Read(&meta_imgraph)) << "Invalid meta graph";
    meta_graph_ = meta_imgraph;
    CHECK(fs->Read(&adj_)) << "Invalid adj matrix";
    return true;
  }
  void Save(dmlc::Stream* fs) const {
    auto meta_graph_ptr = ImmutableGraph::ToImmutable(meta_graph());
    fs->Write(meta_graph_ptr);
    fs->Write(adj_);
  }

800
 private:
801
802
  friend class Serializer;

803
804
805
806
807
808
  /*! \brief internal adjacency matrix. Data array stores edge ids */
  aten::CSRMatrix adj_;
};

//////////////////////////////////////////////////////////
//
Minjie Wang's avatar
Minjie Wang committed
809
// unit graph implementation
810
811
812
//
//////////////////////////////////////////////////////////

813
814
815
816
DLDataType UnitGraph::DataType() const {
  return GetAny()->DataType();
}

Minjie Wang's avatar
Minjie Wang committed
817
DLContext UnitGraph::Context() const {
818
819
820
  return GetAny()->Context();
}

Minjie Wang's avatar
Minjie Wang committed
821
uint8_t UnitGraph::NumBits() const {
822
823
824
  return GetAny()->NumBits();
}

Minjie Wang's avatar
Minjie Wang committed
825
bool UnitGraph::IsMultigraph() const {
826
827
828
  const SparseFormat fmt = SelectFormat(csc_code);
  const auto ptr = GetFormat(fmt);
  return ptr->IsMultigraph();
829
830
}

Minjie Wang's avatar
Minjie Wang committed
831
uint64_t UnitGraph::NumVertices(dgl_type_t vtype) const {
832
  const SparseFormat fmt = SelectFormat(all_code);
833
834
835
  const auto ptr = GetFormat(fmt);
  // TODO(BarclayII): we have a lot of special handling for CSC.
  // Need to have a UnitGraph::CSC backend instead.
836
  if (fmt == SparseFormat::kCSC)
Minjie Wang's avatar
Minjie Wang committed
837
    vtype = (vtype == SrcType()) ? DstType() : SrcType();
838
  return ptr->NumVertices(vtype);
839
840
}

Minjie Wang's avatar
Minjie Wang committed
841
uint64_t UnitGraph::NumEdges(dgl_type_t etype) const {
842
843
844
  return GetAny()->NumEdges(etype);
}

Minjie Wang's avatar
Minjie Wang committed
845
bool UnitGraph::HasVertex(dgl_type_t vtype, dgl_id_t vid) const {
846
  const SparseFormat fmt = SelectFormat(all_code);
847
  const auto ptr = GetFormat(fmt);
848
  if (fmt == SparseFormat::kCSC)
Minjie Wang's avatar
Minjie Wang committed
849
    vtype = (vtype == SrcType()) ? DstType() : SrcType();
850
  return ptr->HasVertex(vtype, vid);
851
852
}

Minjie Wang's avatar
Minjie Wang committed
853
BoolArray UnitGraph::HasVertices(dgl_type_t vtype, IdArray vids) const {
854
  CHECK(aten::IsValidIdArray(vids)) << "Invalid id array input";
855
856
857
  return aten::LT(vids, NumVertices(vtype));
}

Minjie Wang's avatar
Minjie Wang committed
858
bool UnitGraph::HasEdgeBetween(dgl_type_t etype, dgl_id_t src, dgl_id_t dst) const {
859
  const SparseFormat fmt = SelectFormat(csc_code);
860
  const auto ptr = GetFormat(fmt);
861
  if (fmt == SparseFormat::kCSC)
862
863
864
    return ptr->HasEdgeBetween(etype, dst, src);
  else
    return ptr->HasEdgeBetween(etype, src, dst);
865
866
}

Minjie Wang's avatar
Minjie Wang committed
867
BoolArray UnitGraph::HasEdgesBetween(
868
    dgl_type_t etype, IdArray src, IdArray dst) const {
869
  const SparseFormat fmt = SelectFormat(csc_code);
870
  const auto ptr = GetFormat(fmt);
871
  if (fmt == SparseFormat::kCSC)
872
873
874
    return ptr->HasEdgesBetween(etype, dst, src);
  else
    return ptr->HasEdgesBetween(etype, src, dst);
875
876
}

Minjie Wang's avatar
Minjie Wang committed
877
IdArray UnitGraph::Predecessors(dgl_type_t etype, dgl_id_t dst) const {
878
  const SparseFormat fmt = SelectFormat(csc_code);
879
  const auto ptr = GetFormat(fmt);
880
  if (fmt == SparseFormat::kCSC)
881
882
883
    return ptr->Successors(etype, dst);
  else
    return ptr->Predecessors(etype, dst);
884
885
}

Minjie Wang's avatar
Minjie Wang committed
886
IdArray UnitGraph::Successors(dgl_type_t etype, dgl_id_t src) const {
887
  const SparseFormat fmt = SelectFormat(csr_code);
888
889
  const auto ptr = GetFormat(fmt);
  return ptr->Successors(etype, src);
890
891
}

Minjie Wang's avatar
Minjie Wang committed
892
IdArray UnitGraph::EdgeId(dgl_type_t etype, dgl_id_t src, dgl_id_t dst) const {
893
  const SparseFormat fmt = SelectFormat(csr_code);
894
  const auto ptr = GetFormat(fmt);
895
  if (fmt == SparseFormat::kCSC)
896
897
898
    return ptr->EdgeId(etype, dst, src);
  else
    return ptr->EdgeId(etype, src, dst);
899
900
}

901
902
EdgeArray UnitGraph::EdgeIdsAll(dgl_type_t etype, IdArray src, IdArray dst) const {
  const SparseFormat fmt = SelectFormat(csr_code);
903
  const auto ptr = GetFormat(fmt);
904
  if (fmt == SparseFormat::kCSC) {
905
    EdgeArray edges = ptr->EdgeIdsAll(etype, dst, src);
906
907
    return EdgeArray{edges.dst, edges.src, edges.id};
  } else {
908
909
910
911
912
913
914
915
916
917
918
    return ptr->EdgeIdsAll(etype, src, dst);
  }
}

IdArray UnitGraph::EdgeIdsOne(dgl_type_t etype, IdArray src, IdArray dst) const {
  const SparseFormat fmt = SelectFormat(csr_code);
  const auto ptr = GetFormat(fmt);
  if (fmt == SparseFormat::kCSC) {
    return ptr->EdgeIdsOne(etype, dst, src);
  } else {
    return ptr->EdgeIdsOne(etype, src, dst);
919
920
921
  }
}

Minjie Wang's avatar
Minjie Wang committed
922
std::pair<dgl_id_t, dgl_id_t> UnitGraph::FindEdge(dgl_type_t etype, dgl_id_t eid) const {
923
  const SparseFormat fmt = SelectFormat(coo_code);
924
925
  const auto ptr = GetFormat(fmt);
  return ptr->FindEdge(etype, eid);
926
927
}

Minjie Wang's avatar
Minjie Wang committed
928
EdgeArray UnitGraph::FindEdges(dgl_type_t etype, IdArray eids) const {
929
  const SparseFormat fmt = SelectFormat(coo_code);
930
931
  const auto ptr = GetFormat(fmt);
  return ptr->FindEdges(etype, eids);
932
933
}

Minjie Wang's avatar
Minjie Wang committed
934
EdgeArray UnitGraph::InEdges(dgl_type_t etype, dgl_id_t vid) const {
935
  const SparseFormat fmt = SelectFormat(csc_code);
936
  const auto ptr = GetFormat(fmt);
937
  if (fmt == SparseFormat::kCSC) {
938
939
940
941
942
    const EdgeArray& ret = ptr->OutEdges(etype, vid);
    return {ret.dst, ret.src, ret.id};
  } else {
    return ptr->InEdges(etype, vid);
  }
943
944
}

Minjie Wang's avatar
Minjie Wang committed
945
EdgeArray UnitGraph::InEdges(dgl_type_t etype, IdArray vids) const {
946
  const SparseFormat fmt = SelectFormat(csc_code);
947
  const auto ptr = GetFormat(fmt);
948
  if (fmt == SparseFormat::kCSC) {
949
950
951
952
953
    const EdgeArray& ret = ptr->OutEdges(etype, vids);
    return {ret.dst, ret.src, ret.id};
  } else {
    return ptr->InEdges(etype, vids);
  }
954
955
}

Minjie Wang's avatar
Minjie Wang committed
956
EdgeArray UnitGraph::OutEdges(dgl_type_t etype, dgl_id_t vid) const {
957
  const SparseFormat fmt = SelectFormat(csr_code);
958
959
  const auto ptr = GetFormat(fmt);
  return ptr->OutEdges(etype, vid);
960
961
}

Minjie Wang's avatar
Minjie Wang committed
962
EdgeArray UnitGraph::OutEdges(dgl_type_t etype, IdArray vids) const {
963
  const SparseFormat fmt = SelectFormat(csr_code);
964
965
  const auto ptr = GetFormat(fmt);
  return ptr->OutEdges(etype, vids);
966
967
}

Minjie Wang's avatar
Minjie Wang committed
968
EdgeArray UnitGraph::Edges(dgl_type_t etype, const std::string &order) const {
969
970
  SparseFormat fmt;
  if (order == std::string("eid")) {
971
    fmt = SelectFormat(coo_code);
972
  } else if (order.empty()) {
973
    // arbitrary order
974
    fmt = SelectFormat(all_code);
975
  } else if (order == std::string("srcdst")) {
976
    fmt = SelectFormat(csr_code);
977
978
  } else {
    LOG(FATAL) << "Unsupported order request: " << order;
979
    return {};
980
  }
981
982

  const auto& edges = GetFormat(fmt)->Edges(etype, order);
983
  if (fmt == SparseFormat::kCSC)
984
985
986
    return EdgeArray{edges.dst, edges.src, edges.id};
  else
    return edges;
987
988
}

Minjie Wang's avatar
Minjie Wang committed
989
uint64_t UnitGraph::InDegree(dgl_type_t etype, dgl_id_t vid) const {
990
  SparseFormat fmt = SelectFormat(csc_code);
991
  const auto ptr = GetFormat(fmt);
992
  if (fmt == SparseFormat::kCSC)
993
994
995
    return ptr->OutDegree(etype, vid);
  else
    return ptr->InDegree(etype, vid);
996
997
}

Minjie Wang's avatar
Minjie Wang committed
998
DegreeArray UnitGraph::InDegrees(dgl_type_t etype, IdArray vids) const {
999
  SparseFormat fmt = SelectFormat(csc_code);
1000
  const auto ptr = GetFormat(fmt);
1001
  if (fmt == SparseFormat::kCSC)
1002
1003
1004
    return ptr->OutDegrees(etype, vids);
  else
    return ptr->InDegrees(etype, vids);
1005
1006
}

Minjie Wang's avatar
Minjie Wang committed
1007
uint64_t UnitGraph::OutDegree(dgl_type_t etype, dgl_id_t vid) const {
1008
  SparseFormat fmt = SelectFormat(csr_code);
1009
1010
  const auto ptr = GetFormat(fmt);
  return ptr->OutDegree(etype, vid);
1011
1012
}

Minjie Wang's avatar
Minjie Wang committed
1013
DegreeArray UnitGraph::OutDegrees(dgl_type_t etype, IdArray vids) const {
1014
  SparseFormat fmt = SelectFormat(csr_code);
1015
1016
  const auto ptr = GetFormat(fmt);
  return ptr->OutDegrees(etype, vids);
1017
1018
}

Minjie Wang's avatar
Minjie Wang committed
1019
DGLIdIters UnitGraph::SuccVec(dgl_type_t etype, dgl_id_t vid) const {
1020
  SparseFormat fmt = SelectFormat(csr_code);
1021
1022
  const auto ptr = GetFormat(fmt);
  return ptr->SuccVec(etype, vid);
1023
1024
}

1025
DGLIdIters32 UnitGraph::SuccVec32(dgl_type_t etype, dgl_id_t vid) const {
1026
  SparseFormat fmt = SelectFormat(csr_code);
1027
1028
1029
1030
1031
  const auto ptr = std::dynamic_pointer_cast<CSR>(GetFormat(fmt));
  CHECK_NOTNULL(ptr);
  return ptr->SuccVec32(etype, vid);
}

Minjie Wang's avatar
Minjie Wang committed
1032
DGLIdIters UnitGraph::OutEdgeVec(dgl_type_t etype, dgl_id_t vid) const {
1033
  SparseFormat fmt = SelectFormat(csr_code);
1034
1035
  const auto ptr = GetFormat(fmt);
  return ptr->OutEdgeVec(etype, vid);
1036
1037
}

Minjie Wang's avatar
Minjie Wang committed
1038
DGLIdIters UnitGraph::PredVec(dgl_type_t etype, dgl_id_t vid) const {
1039
  SparseFormat fmt = SelectFormat(csc_code);
1040
  const auto ptr = GetFormat(fmt);
1041
  if (fmt == SparseFormat::kCSC)
1042
1043
1044
    return ptr->SuccVec(etype, vid);
  else
    return ptr->PredVec(etype, vid);
1045
1046
}

Minjie Wang's avatar
Minjie Wang committed
1047
DGLIdIters UnitGraph::InEdgeVec(dgl_type_t etype, dgl_id_t vid) const {
1048
  SparseFormat fmt = SelectFormat(csc_code);
1049
  const auto ptr = GetFormat(fmt);
1050
  if (fmt == SparseFormat::kCSC)
1051
1052
1053
    return ptr->OutEdgeVec(etype, vid);
  else
    return ptr->InEdgeVec(etype, vid);
1054
1055
}

Minjie Wang's avatar
Minjie Wang committed
1056
std::vector<IdArray> UnitGraph::GetAdj(
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
    dgl_type_t etype, bool transpose, const std::string &fmt) const {
  // TODO(minjie): Our current semantics of adjacency matrix is row for dst nodes and col for
  //   src nodes. Therefore, we need to flip the transpose flag. For example, transpose=False
  //   is equal to in edge CSR.
  //   We have this behavior because previously we use framework's SPMM and we don't cache
  //   reverse adj. This is not intuitive and also not consistent with networkx's
  //   to_scipy_sparse_matrix. With the upcoming custom kernel change, we should change the
  //   behavior and make row for src and col for dst.
  if (fmt == std::string("csr")) {
    return transpose? GetOutCSR()->GetAdj(etype, false, "csr")
      : GetInCSR()->GetAdj(etype, false, "csr");
  } else if (fmt == std::string("coo")) {
    return GetCOO()->GetAdj(etype, !transpose, fmt);
  } else {
    LOG(FATAL) << "unsupported adjacency matrix format: " << fmt;
    return {};
  }
}

Minjie Wang's avatar
Minjie Wang committed
1076
HeteroSubgraph UnitGraph::VertexSubgraph(const std::vector<IdArray>& vids) const {
1077
  // We prefer to generate a subgraph from out-csr.
1078
  SparseFormat fmt = SelectFormat(csr_code);
1079
  HeteroSubgraph sg = GetFormat(fmt)->VertexSubgraph(vids);
1080
  HeteroSubgraph ret;
Quan (Andy) Gan's avatar
Quan (Andy) Gan committed
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100

  CSRPtr subcsr = nullptr;
  CSRPtr subcsc = nullptr;
  COOPtr subcoo = nullptr;
  switch (fmt) {
    case SparseFormat::kCSR:
      subcsr = std::dynamic_pointer_cast<CSR>(sg.graph);
      break;
    case SparseFormat::kCSC:
      subcsc = std::dynamic_pointer_cast<CSR>(sg.graph);
      break;
    case SparseFormat::kCOO:
      subcoo = std::dynamic_pointer_cast<COO>(sg.graph);
      break;
    default:
      LOG(FATAL) << "[BUG] unsupported format " << static_cast<int>(fmt);
      return ret;
  }

  ret.graph = HeteroGraphPtr(new UnitGraph(meta_graph(), subcsc, subcsr, subcoo));
1101
1102
1103
1104
1105
  ret.induced_vertices = std::move(sg.induced_vertices);
  ret.induced_edges = std::move(sg.induced_edges);
  return ret;
}

Minjie Wang's avatar
Minjie Wang committed
1106
HeteroSubgraph UnitGraph::EdgeSubgraph(
1107
    const std::vector<IdArray>& eids, bool preserve_nodes) const {
1108
  SparseFormat fmt = SelectFormat(coo_code);
1109
  auto sg = GetFormat(fmt)->EdgeSubgraph(eids, preserve_nodes);
1110
  HeteroSubgraph ret;
Quan (Andy) Gan's avatar
Quan (Andy) Gan committed
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130

  CSRPtr subcsr = nullptr;
  CSRPtr subcsc = nullptr;
  COOPtr subcoo = nullptr;
  switch (fmt) {
    case SparseFormat::kCSR:
      subcsr = std::dynamic_pointer_cast<CSR>(sg.graph);
      break;
    case SparseFormat::kCSC:
      subcsc = std::dynamic_pointer_cast<CSR>(sg.graph);
      break;
    case SparseFormat::kCOO:
      subcoo = std::dynamic_pointer_cast<COO>(sg.graph);
      break;
    default:
      LOG(FATAL) << "[BUG] unsupported format " << static_cast<int>(fmt);
      return ret;
  }

  ret.graph = HeteroGraphPtr(new UnitGraph(meta_graph(), subcsc, subcsr, subcoo));
1131
1132
1133
1134
1135
  ret.induced_vertices = std::move(sg.induced_vertices);
  ret.induced_edges = std::move(sg.induced_edges);
  return ret;
}

Minjie Wang's avatar
Minjie Wang committed
1136
HeteroGraphPtr UnitGraph::CreateFromCOO(
1137
1138
    int64_t num_vtypes, int64_t num_src, int64_t num_dst,
    IdArray row, IdArray col,
1139
    dgl_format_code_t formats) {
Minjie Wang's avatar
Minjie Wang committed
1140
1141
1142
1143
1144
  CHECK(num_vtypes == 1 || num_vtypes == 2);
  if (num_vtypes == 1)
    CHECK_EQ(num_src, num_dst);
  auto mg = CreateUnitGraphMetaGraph(num_vtypes);
  COOPtr coo(new COO(mg, num_src, num_dst, row, col));
1145
1146

  return HeteroGraphPtr(
1147
      new UnitGraph(mg, nullptr, nullptr, coo, formats));
1148
1149
}

1150
1151
HeteroGraphPtr UnitGraph::CreateFromCOO(
    int64_t num_vtypes, const aten::COOMatrix& mat,
1152
    dgl_format_code_t formats) {
1153
1154
1155
1156
1157
  CHECK(num_vtypes == 1 || num_vtypes == 2);
  if (num_vtypes == 1)
    CHECK_EQ(mat.num_rows, mat.num_cols);
  auto mg = CreateUnitGraphMetaGraph(num_vtypes);
  COOPtr coo(new COO(mg, mat));
1158

1159
  return HeteroGraphPtr(
1160
      new UnitGraph(mg, nullptr, nullptr, coo, formats));
1161
1162
}

Minjie Wang's avatar
Minjie Wang committed
1163
1164
HeteroGraphPtr UnitGraph::CreateFromCSR(
    int64_t num_vtypes, int64_t num_src, int64_t num_dst,
1165
    IdArray indptr, IdArray indices, IdArray edge_ids, dgl_format_code_t formats) {
Minjie Wang's avatar
Minjie Wang committed
1166
1167
1168
1169
1170
  CHECK(num_vtypes == 1 || num_vtypes == 2);
  if (num_vtypes == 1)
    CHECK_EQ(num_src, num_dst);
  auto mg = CreateUnitGraphMetaGraph(num_vtypes);
  CSRPtr csr(new CSR(mg, num_src, num_dst, indptr, indices, edge_ids));
1171
  return HeteroGraphPtr(new UnitGraph(mg, nullptr, csr, nullptr, formats));
1172
1173
}

1174
1175
HeteroGraphPtr UnitGraph::CreateFromCSR(
    int64_t num_vtypes, const aten::CSRMatrix& mat,
1176
    dgl_format_code_t formats) {
1177
1178
1179
1180
1181
  CHECK(num_vtypes == 1 || num_vtypes == 2);
  if (num_vtypes == 1)
    CHECK_EQ(mat.num_rows, mat.num_cols);
  auto mg = CreateUnitGraphMetaGraph(num_vtypes);
  CSRPtr csr(new CSR(mg, mat));
1182
  return HeteroGraphPtr(new UnitGraph(mg, nullptr, csr, nullptr, formats));
1183
1184
}

1185
1186
HeteroGraphPtr UnitGraph::CreateFromCSC(
    int64_t num_vtypes, int64_t num_src, int64_t num_dst,
1187
    IdArray indptr, IdArray indices, IdArray edge_ids, dgl_format_code_t formats) {
1188
1189
1190
1191
1192
  CHECK(num_vtypes == 1 || num_vtypes == 2);
  if (num_vtypes == 1)
    CHECK_EQ(num_src, num_dst);
  auto mg = CreateUnitGraphMetaGraph(num_vtypes);
  CSRPtr csc(new CSR(mg, num_src, num_dst, indptr, indices, edge_ids));
1193
  return HeteroGraphPtr(new UnitGraph(mg, csc, nullptr, nullptr, formats));
1194
1195
1196
1197
}

HeteroGraphPtr UnitGraph::CreateFromCSC(
    int64_t num_vtypes, const aten::CSRMatrix& mat,
1198
    dgl_format_code_t formats) {
1199
1200
1201
1202
1203
  CHECK(num_vtypes == 1 || num_vtypes == 2);
  if (num_vtypes == 1)
    CHECK_EQ(mat.num_rows, mat.num_cols);
  auto mg = CreateUnitGraphMetaGraph(num_vtypes);
  CSRPtr csc(new CSR(mg, mat));
1204
  return HeteroGraphPtr(new UnitGraph(mg, csc, nullptr, nullptr, formats));
1205
1206
}

Minjie Wang's avatar
Minjie Wang committed
1207
HeteroGraphPtr UnitGraph::AsNumBits(HeteroGraphPtr g, uint8_t bits) {
1208
1209
1210
  if (g->NumBits() == bits) {
    return g;
  } else {
Minjie Wang's avatar
Minjie Wang committed
1211
    auto bg = std::dynamic_pointer_cast<UnitGraph>(g);
1212
    CHECK_NOTNULL(bg);
1213
1214
1215
1216
1217
1218
    CSRPtr new_incsr =
      (bg->in_csr_->defined())? CSRPtr(new CSR(bg->in_csr_->AsNumBits(bits))) : nullptr;
    CSRPtr new_outcsr =
      (bg->out_csr_->defined())? CSRPtr(new CSR(bg->out_csr_->AsNumBits(bits))) : nullptr;
    COOPtr new_coo =
      (bg->coo_->defined())? COOPtr(new COO(bg->coo_->AsNumBits(bits))) : nullptr;
1219
    return HeteroGraphPtr(
1220
        new UnitGraph(g->meta_graph(), new_incsr, new_outcsr, new_coo, bg->formats_));
1221
1222
1223
  }
}

Minjie Wang's avatar
Minjie Wang committed
1224
HeteroGraphPtr UnitGraph::CopyTo(HeteroGraphPtr g, const DLContext& ctx) {
1225
1226
  if (ctx == g->Context()) {
    return g;
1227
1228
1229
  } else {
    auto bg = std::dynamic_pointer_cast<UnitGraph>(g);
    CHECK_NOTNULL(bg);
1230
1231
1232
1233
1234
1235
    CSRPtr new_incsr =
      (bg->in_csr_->defined())? CSRPtr(new CSR(bg->in_csr_->CopyTo(ctx))) : nullptr;
    CSRPtr new_outcsr =
      (bg->out_csr_->defined())? CSRPtr(new CSR(bg->out_csr_->CopyTo(ctx))) : nullptr;
    COOPtr new_coo =
      (bg->coo_->defined())? COOPtr(new COO(bg->coo_->CopyTo(ctx))) : nullptr;
1236
    return HeteroGraphPtr(
1237
        new UnitGraph(g->meta_graph(), new_incsr, new_outcsr, new_coo, bg->formats_));
1238
1239
1240
  }
}

1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
void UnitGraph::InvalidateCSR() {
  this->out_csr_ = CSRPtr(new CSR());
}

void UnitGraph::InvalidateCSC() {
  this->in_csr_ = CSRPtr(new CSR());
}

void UnitGraph::InvalidateCOO() {
  this->coo_ = COOPtr(new COO());
}

1253
UnitGraph::UnitGraph(GraphPtr metagraph, CSRPtr in_csr, CSRPtr out_csr, COOPtr coo,
1254
                     dgl_format_code_t formats)
Minjie Wang's avatar
Minjie Wang committed
1255
  : BaseHeteroGraph(metagraph), in_csr_(in_csr), out_csr_(out_csr), coo_(coo) {
1256
1257
1258
1259
1260
1261
1262
1263
1264
  if (!in_csr_) {
    in_csr_ = CSRPtr(new CSR());
  }
  if (!out_csr_) {
    out_csr_ = CSRPtr(new CSR());
  }
  if (!coo_) {
    coo_ = COOPtr(new COO());
  }
1265
1266
1267
1268
1269
  formats_ = formats;
  dgl_format_code_t created = GetCreatedFormats();
  if ((formats | created) != formats)
    LOG(FATAL) << "Graph created from formats: " << CodeToStr(created) <<
      ", which is not compatible with available formats: " << CodeToStr(formats);
1270
1271
1272
  CHECK(GetAny()) << "At least one graph structure should exist.";
}

1273
1274
1275
1276
1277
1278
1279
HeteroGraphPtr UnitGraph::CreateHomographFrom(
    const aten::CSRMatrix &in_csr,
    const aten::CSRMatrix &out_csr,
    const aten::COOMatrix &coo,
    bool has_in_csr,
    bool has_out_csr,
    bool has_coo,
1280
    dgl_format_code_t formats) {
1281
1282
1283
1284
1285
1286
1287
1288
  auto mg = CreateUnitGraphMetaGraph1();

  CSRPtr in_csr_ptr = nullptr;
  CSRPtr out_csr_ptr = nullptr;
  COOPtr coo_ptr = nullptr;

  if (has_in_csr)
    in_csr_ptr = CSRPtr(new CSR(mg, in_csr));
1289
1290
  else
    in_csr_ptr = CSRPtr(new CSR());
1291
1292
  if (has_out_csr)
    out_csr_ptr = CSRPtr(new CSR(mg, out_csr));
1293
1294
  else
    out_csr_ptr = CSRPtr(new CSR());
1295
1296
  if (has_coo)
    coo_ptr = COOPtr(new COO(mg, coo));
1297
1298
  else
    coo_ptr = COOPtr(new COO());
1299

1300
  return HeteroGraphPtr(new UnitGraph(mg, in_csr_ptr, out_csr_ptr, coo_ptr, formats));
1301
1302
}

1303
1304
UnitGraph::CSRPtr UnitGraph::GetInCSR(bool inplace) const {
  if (inplace)
1305
1306
1307
    if (!(formats_ & csc_code))
      LOG(FATAL) << "The graph have restricted sparse format " <<
        CodeToStr(formats_) << ", cannot create CSC matrix.";
1308
  CSRPtr ret = in_csr_;
1309
1310
  if (!in_csr_->defined()) {
    if (out_csr_->defined()) {
1311
      const auto& newadj = aten::CSRSort(aten::CSRTranspose(out_csr_->adj()));
1312

1313
      if (inplace)
1314
1315
1316
        *(const_cast<UnitGraph*>(this)->in_csr_) = CSR(meta_graph(), newadj);
      else
        ret = std::make_shared<CSR>(meta_graph(), newadj);
1317
    } else {
1318
      CHECK(coo_->defined()) << "None of CSR, COO exist";
1319
1320
      const auto& newadj = aten::CSRSort(aten::COOToCSR(
            aten::COOTranspose(coo_->adj())));
1321

1322
      if (inplace)
1323
1324
1325
        *(const_cast<UnitGraph*>(this)->in_csr_) = CSR(meta_graph(), newadj);
      else
        ret = std::make_shared<CSR>(meta_graph(), newadj);
1326
1327
    }
  }
1328
  return ret;
1329
1330
1331
}

/* !\brief Return out csr. If not exist, transpose the other one.*/
1332
1333
UnitGraph::CSRPtr UnitGraph::GetOutCSR(bool inplace) const {
  if (inplace)
1334
1335
1336
    if (!(formats_ & csr_code))
      LOG(FATAL) << "The graph have restricted sparse format " <<
        CodeToStr(formats_) << ", cannot create CSR matrix.";
1337
  CSRPtr ret = out_csr_;
1338
1339
  if (!out_csr_->defined()) {
    if (in_csr_->defined()) {
1340
      const auto& newadj = aten::CSRSort(aten::CSRTranspose(in_csr_->adj()));
1341

1342
      if (inplace)
1343
1344
1345
        *(const_cast<UnitGraph*>(this)->out_csr_) = CSR(meta_graph(), newadj);
      else
        ret = std::make_shared<CSR>(meta_graph(), newadj);
1346
    } else {
1347
      CHECK(coo_->defined()) << "None of CSR, COO exist";
1348
      const auto& newadj = aten::CSRSort(aten::COOToCSR(coo_->adj()));
1349

1350
      if (inplace)
1351
1352
1353
        *(const_cast<UnitGraph*>(this)->out_csr_) = CSR(meta_graph(), newadj);
      else
        ret = std::make_shared<CSR>(meta_graph(), newadj);
1354
1355
    }
  }
1356
  return ret;
1357
1358
1359
}

/* !\brief Return coo. If not exist, create from csr.*/
1360
1361
UnitGraph::COOPtr UnitGraph::GetCOO(bool inplace) const {
  if (inplace)
1362
1363
1364
    if (!(formats_ & coo_code))
      LOG(FATAL) << "The graph have restricted sparse format " <<
        CodeToStr(formats_) << ", cannot create COO matrix.";
1365
  COOPtr ret = coo_;
1366
1367
  if (!coo_->defined()) {
    if (in_csr_->defined()) {
1368
      const auto& newadj = aten::COOTranspose(aten::CSRToCOO(in_csr_->adj(), true));
1369

1370
      if (inplace)
1371
1372
1373
        *(const_cast<UnitGraph*>(this)->coo_) = COO(meta_graph(), newadj);
      else
        ret = std::make_shared<COO>(meta_graph(), newadj);
1374
    } else {
1375
      CHECK(out_csr_->defined()) << "Both CSR are missing.";
1376
      const auto& newadj = aten::CSRToCOO(out_csr_->adj(), true);
1377

1378
      if (inplace)
1379
1380
1381
        *(const_cast<UnitGraph*>(this)->coo_) = COO(meta_graph(), newadj);
      else
        ret = std::make_shared<COO>(meta_graph(), newadj);
1382
1383
    }
  }
1384
  return ret;
1385
1386
}

1387
aten::CSRMatrix UnitGraph::GetCSCMatrix(dgl_type_t etype) const {
1388
1389
1390
  return GetInCSR()->adj();
}

1391
aten::CSRMatrix UnitGraph::GetCSRMatrix(dgl_type_t etype) const {
1392
1393
1394
  return GetOutCSR()->adj();
}

1395
aten::COOMatrix UnitGraph::GetCOOMatrix(dgl_type_t etype) const {
1396
1397
1398
  return GetCOO()->adj();
}

Minjie Wang's avatar
Minjie Wang committed
1399
HeteroGraphPtr UnitGraph::GetAny() const {
1400
  if (in_csr_->defined()) {
1401
    return in_csr_;
1402
  } else if (out_csr_->defined()) {
1403
1404
1405
1406
1407
1408
    return out_csr_;
  } else {
    return coo_;
  }
}

1409
dgl_format_code_t UnitGraph::GetCreatedFormats() const {
1410
  dgl_format_code_t ret = 0;
1411
1412
1413
1414
1415
1416
  if (in_csr_->defined())
    ret |= csc_code;
  if (out_csr_->defined())
    ret |= csr_code;
  if (coo_->defined())
    ret |= coo_code;
1417
1418
1419
  return ret;
}

1420
1421
1422
1423
dgl_format_code_t UnitGraph::GetAllowedFormats() const {
  return formats_;
}

1424
1425
HeteroGraphPtr UnitGraph::GetFormat(SparseFormat format) const {
  switch (format) {
1426
1427
1428
1429
  case SparseFormat::kCSR:
    return GetOutCSR();
  case SparseFormat::kCSC:
    return GetInCSR();
1430
  default:
1431
    return GetCOO();
1432
1433
1434
  }
}

1435
1436
1437
HeteroGraphPtr UnitGraph::GetGraphInFormat(dgl_format_code_t formats) const {
  if (formats == all_code)
    return HeteroGraphPtr(
1438
1439
        // TODO(xiangsx) Make it as graph storage.Clone()
        new UnitGraph(meta_graph_,
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
                      (in_csr_->defined())
                          ? CSRPtr(new CSR(*in_csr_))
                          : nullptr,
                      (out_csr_->defined())
                          ? CSRPtr(new CSR(*out_csr_))
                          : nullptr,
                      (coo_->defined())
                          ? COOPtr(new COO(*coo_))
                          : nullptr,
                      formats));
  int64_t num_vtypes = NumVertexTypes();
  if (formats & coo_code)
    return CreateFromCOO(num_vtypes, GetCOO(false)->adj(), formats);
  if (formats & csr_code)
    return CreateFromCSR(num_vtypes, GetOutCSR(false)->adj(), formats);
  return CreateFromCSC(num_vtypes, GetInCSR(false)->adj(), formats);
}

SparseFormat UnitGraph::SelectFormat(dgl_format_code_t preferred_formats) const {
  dgl_format_code_t common = preferred_formats & formats_;
  dgl_format_code_t created = GetCreatedFormats();
  if (common & created)
    return DecodeFormat(common & created);
1463
1464
1465
1466
1467

  // NOTE(zihao): hypersparse is currently disabled since many CUDA operators on COO have
  // not been implmented yet.
  // if (coo_->defined() && coo_->IsHypersparse())  // only allow coo for hypersparse graph.
  //   return SparseFormat::kCOO;
1468
1469
1470
  if (common)
    return DecodeFormat(common);
  return DecodeFormat(created);
1471
1472
}

1473
1474
1475
1476
GraphPtr UnitGraph::AsImmutableGraph() const {
  CHECK(NumVertexTypes() == 1) << "not a homogeneous graph";
  dgl::CSRPtr in_csr_ptr = nullptr, out_csr_ptr = nullptr;
  dgl::COOPtr coo_ptr = nullptr;
1477
  if (in_csr_->defined()) {
1478
    aten::CSRMatrix csc = GetCSCMatrix(0);
1479
    in_csr_ptr = dgl::CSRPtr(new dgl::CSR(csc.indptr, csc.indices, csc.data));
1480
  }
1481
  if (out_csr_->defined()) {
1482
    aten::CSRMatrix csr = GetCSRMatrix(0);
1483
    out_csr_ptr = dgl::CSRPtr(new dgl::CSR(csr.indptr, csr.indices, csr.data));
1484
  }
1485
  if (coo_->defined()) {
1486
1487
    aten::COOMatrix coo = GetCOOMatrix(0);
    if (!COOHasData(coo)) {
1488
      coo_ptr = dgl::COOPtr(new dgl::COO(NumVertices(0), coo.row, coo.col));
1489
1490
1491
    } else {
      IdArray new_src = Scatter(coo.row, coo.data);
      IdArray new_dst = Scatter(coo.col, coo.data);
1492
      coo_ptr = dgl::COOPtr(new dgl::COO(NumVertices(0), new_src, new_dst));
1493
1494
1495
1496
1497
    }
  }
  return GraphPtr(new dgl::ImmutableGraph(in_csr_ptr, out_csr_ptr, coo_ptr));
}

1498
1499
HeteroGraphPtr UnitGraph::LineGraph(bool backtracking) const {
  // TODO(xiangsx) currently we only support homogeneous graph
1500
  auto fmt = SelectFormat(all_code);
1501
1502
  switch (fmt) {
    case SparseFormat::kCOO: {
1503
      return CreateFromCOO(1, aten::COOLineGraph(coo_->adj(), backtracking));
1504
1505
1506
1507
    }
    case SparseFormat::kCSR: {
      const aten::CSRMatrix csr = GetCSRMatrix(0);
      const aten::COOMatrix coo = aten::COOLineGraph(aten::CSRToCOO(csr, true), backtracking);
1508
      return CreateFromCOO(1, coo);
1509
1510
1511
1512
1513
    }
    case SparseFormat::kCSC: {
      const aten::CSRMatrix csc = GetCSCMatrix(0);
      const aten::CSRMatrix csr = aten::CSRTranspose(csc);
      const aten::COOMatrix coo = aten::COOLineGraph(aten::CSRToCOO(csr, true), backtracking);
1514
      return CreateFromCOO(1, coo);
1515
1516
1517
1518
1519
1520
1521
1522
    }
    default:
      LOG(FATAL) << "None of CSC, CSR, COO exist";
      break;
  }
  return nullptr;
}

1523
1524
1525
1526
1527
1528
constexpr uint64_t kDGLSerialize_UnitGraphMagic = 0xDD2E60F0F6B4A127;

bool UnitGraph::Load(dmlc::Stream* fs) {
  uint64_t magicNum;
  CHECK(fs->Read(&magicNum)) << "Invalid Magic Number";
  CHECK_EQ(magicNum, kDGLSerialize_UnitGraphMagic) << "Invalid UnitGraph Data";
1529

1530
  int64_t save_format_code, formats_code;
1531
  CHECK(fs->Read(&save_format_code)) << "Invalid format";
1532
  CHECK(fs->Read(&formats_code)) << "Invalid format";
1533
  auto save_format = static_cast<SparseFormat>(save_format_code);
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
  if (formats_code >> 32) {
    formats_ = static_cast<dgl_format_code_t>(0xffffffff & formats_code);
  } else {
    // NOTE(zihao): to be compatible with old formats.
    switch (formats_code & 0xffffffff) {
    case 0:
      formats_ = all_code;
      break;
    case 1:
      formats_ = coo_code;
      break;
    case 2:
      formats_ = csr_code;
      break;
    case 3:
      formats_ = csc_code;
      break;
    default:
      LOG(FATAL) << "Load graph failed, formats code " << formats_code <<
        "not recognized.";
    }
  }
1556

1557
  switch (save_format) {
1558
    case SparseFormat::kCOO:
1559
1560
      fs->Read(&coo_);
      break;
1561
    case SparseFormat::kCSR:
1562
1563
      fs->Read(&out_csr_);
      break;
1564
    case SparseFormat::kCSC:
1565
1566
1567
1568
1569
1570
1571
      fs->Read(&in_csr_);
      break;
    default:
      LOG(FATAL) << "unsupported format code";
      break;
  }

1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
  if (!in_csr_) {
    in_csr_ = CSRPtr(new CSR());
  }
  if (!out_csr_) {
    out_csr_ = CSRPtr(new CSR());
  }
  if (!coo_) {
    coo_ = COOPtr(new COO());
  }

1582
1583
  meta_graph_ = GetAny()->meta_graph();

1584
1585
1586
  return true;
}

1587

1588
1589
void UnitGraph::Save(dmlc::Stream* fs) const {
  fs->Write(kDGLSerialize_UnitGraphMagic);
1590
1591
  // Didn't write UnitGraph::meta_graph_, since it's included in the underlying
  // sparse matrix
1592
  auto avail_fmt = SelectFormat(all_code);
1593
  fs->Write(static_cast<int64_t>(avail_fmt));
1594
  fs->Write(static_cast<int64_t>(formats_ | 0x100000000));
1595
  switch (avail_fmt) {
1596
    case SparseFormat::kCOO:
1597
1598
      fs->Write(GetCOO());
      break;
1599
    case SparseFormat::kCSR:
1600
1601
      fs->Write(GetOutCSR());
      break;
1602
    case SparseFormat::kCSC:
1603
1604
1605
1606
1607
1608
      fs->Write(GetInCSR());
      break;
    default:
      LOG(FATAL) << "unsupported format code";
      break;
  }
1609
1610
}

1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
UnitGraphPtr UnitGraph::Reverse() const {
  CSRPtr new_incsr = out_csr_, new_outcsr = in_csr_;
  COOPtr new_coo = nullptr;
  if (coo_->defined()) {
    new_coo = COOPtr(new COO(coo_->meta_graph(), aten::COOTranspose(coo_->adj())));
  }

  return UnitGraphPtr(new UnitGraph(meta_graph(), new_incsr, new_outcsr, new_coo));
}

1621
1622
1623
1624
1625
1626
1627
std::tuple<UnitGraphPtr, IdArray, IdArray>
UnitGraph::ToSimple() const {
  CSRPtr new_incsr = nullptr, new_outcsr = nullptr;
  COOPtr new_coo = nullptr;
  IdArray count;
  IdArray edge_map;

1628
  auto avail_fmt = SelectFormat(all_code);
1629
1630
  switch (avail_fmt) {
    case SparseFormat::kCOO: {
1631
      auto ret = aten::COOToSimple(GetCOO()->adj());
1632
1633
      count = std::get<1>(ret);
      edge_map = std::get<2>(ret);
1634
      new_coo = COOPtr(new COO(meta_graph(), std::get<0>(ret)));
1635
1636
1637
      break;
    }
    case SparseFormat::kCSR: {
1638
      auto ret = aten::CSRToSimple(GetOutCSR()->adj());
1639
1640
      count = std::get<1>(ret);
      edge_map = std::get<2>(ret);
1641
      new_outcsr = CSRPtr(new CSR(meta_graph(), std::get<0>(ret)));
1642
1643
1644
      break;
    }
    case SparseFormat::kCSC: {
1645
      auto ret = aten::CSRToSimple(GetInCSR()->adj());
1646
1647
      count = std::get<1>(ret);
      edge_map = std::get<2>(ret);
1648
      new_incsr = CSRPtr(new CSR(meta_graph(), std::get<0>(ret)));
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
      break;
    }
    default:
      LOG(FATAL) << "At lease one of COO, CSR or CSC adj should exist.";
      break;
  }

  return std::make_tuple(UnitGraphPtr(new UnitGraph(meta_graph(), new_incsr, new_outcsr, new_coo)),
                         count,
                         edge_map);
}

1661
}  // namespace dgl