Added fixes for the case that matmullt dim A is zero, e.g. [0, 768].

bitsandbytes/autograd/_functions.py

 import torch
+import math
 import bitsandbytes as bnb
 import bitsandbytes.functional as F
 
@@ -162,6 +163,17 @@ class MatMul8bitLt(torch.autograd.Function):
 
     @staticmethod
     def forward(ctx, A, B, out=None, state=MatmulLtState()):
+        # default to pytorch behavior if inputs are empty
+        ctx.is_empty = False
+        if math.prod(A.shape) == 0:
+            ctx.is_empty = True
+            ctx.A = A
+            ctx.B = B
+            if A.shape[-1] == B.shape[0]:
+                return torch.empty(A.shape[:-1]+B.shape[1:], dtype=torch.float16, device=A.device)
+            else:
+                return torch.empty(A.shape[:-1]+B.shape[:1], dtype=torch.float16, device=A.device)
+
         # 1. Quantize A
         # 2. Quantize B
         # 3. Matmul
@@ -265,6 +277,8 @@ class MatMul8bitLt(torch.autograd.Function):
 
     @staticmethod
     def backward(ctx, grad_output):
+        if ctx.is_empty:
+            return torch.zeros_like(ctx.A), torch.zeros_like(ctx.B), None, None
         req_gradA, req_gradB = ctx.req_grads
         CAt, subA = ctx.tensors
         SCAt, idx = ctx.tensor_states
@@ -293,7 +307,7 @@ class MatMul8bitLt(torch.autograd.Function):
             gradA32, SgradA32 = F.igemmlt(C32grad, state.CxBt, Sgrad, state.SBt)
             grad_A = F.mm_dequant(gradA32, SgradA32, SCgrad, state.SCBt).view(ctx.grad_shape)
 
-        return grad_A, grad_B, None, None, None, None, None
+        return grad_A, grad_B, None, None
 
 
 matmul = MatMul8bitLt.apply

bitsandbytes/functional.py

@@ -4,9 +4,10 @@
 # LICENSE file in the root directory of this source tree.
 import ctypes as ct
 import random
-from typing import Tuple
-
+import math
 import torch
+
+from typing import Tuple
 from torch import Tensor
 
 from .cextension import lib, COMPILED_WITH_CUDA
@@ -919,15 +920,22 @@ def igemmlt(A, B, SA, SB, out=None, Sout=None, dtype=torch.int32):
     shapeB = SB[0]
     dimsA = len(shapeA)
     dimsB = len(shapeB)
+    assert dimsB == 2, 'Only two dimensional matrices are supported for argument B'
     if dimsA == 2:
         m = shapeA[0]
     elif dimsA == 3:
         m = shapeA[0]*shapeA[1]
 
-    if dimsB == 2:
-        rows = n = shapeB[0]
-    elif dimsB == 3:
-        rows = n = shapeB[0]*shapeB[1]
+    rows = n = shapeB[0]
+    assert math.prod(list(shapeA)) > 0, f'Input tensor dimensions need to be > 0: {shapeA}'
+    print(shapeA, math.prod(shapeA), math.prod(list(shapeA)))
+    print('aaa')
+
+    # if the tensor is empty, return a transformed empty tensor with the right dimensions
+    if shapeA[0] == 0 and dimsA == 2:
+        return torch.empty((0, shapeB[0]), device=A.device, dtype=torch.float16)
+    elif shapeA[1] == 0 and dimsA == 3:
+        return torch.empty(tuple(shapeA[:2] + [shapeB[0]]), device=A.device, dtype=torch.float16)
 
     if dimsA == 2 and out is None:
         out, Sout = get_transform_buffer((shapeA[0], shapeB[0]), dtype, A.device, 'col32', 'row')
@@ -984,6 +992,7 @@ def igemmlt(A, B, SA, SB, out=None, Sout=None, dtype=torch.int32):
             has_error = lib.cigemmlt_ampere_8(ptr, m, n, k, ptrA, ptrB, ptrC, ptrRowScale, lda, ldb, ldc)
 
     if has_error == 1:
+        print(f'A: {shapeA}, B: {shapeB}, C: {Sout[0]}; (lda, ldb, ldc): {(lda, ldb, ldc)}; (m, n, k): {(m, n, k)}')
         raise Exception('cublasLt ran into an error!')
 
     torch.cuda.set_device(prev_device)

csrc/ops.cu

@@ -459,8 +459,6 @@ void dequant_mm_int32_fp16(int *A, float *rowStats, float *colStats, half *out,
   assert(num_blocks <= 65535 && "CUDA ERROR: Maximum number of blocks for kernel exceeded");
   assert(threads <= tilesize);
 
-  //cout << num_blocks << " blocks" << endl;
-
   kdequant_mm_int32_fp16<4, 128, 512><<<num_blocks, threads>>>(A, rowStats, colStats, out, newRowStats, newcolStats, numRows, numCols, tileCols, n);
   CUDA_CHECK_RETURN(cudaPeekAtLastError());
 }
@@ -473,11 +471,14 @@ void getColRowStats(half * A, float *rowStats, float *colStats, int *nnz_count_r
   int tile_cols = STATS_THREADS*STATS_ITEMS;
   int tiledCols = fill_up_to_nearest_multiple(cols, tile_cols);
   int tiledRows = fill_up_to_nearest_multiple(rows, STATS_ROWS);
-  int num_blocks = (tiledCols/tile_cols) * (tiledRows/STATS_ROWS);
+	int row_tiles = (tiledRows/STATS_ROWS);
+	int col_tiles = (tiledCols/tile_cols);
+	row_tiles = row_tiles > 0 ? row_tiles : 1;
+	col_tiles = col_tiles > 0 ? col_tiles : 1;
+  int num_blocks = row_tiles * col_tiles;
 
   assert(num_blocks <= 65535 && "CUDA ERROR: Maximum number of blocks for kernel exceeded");
 
-
   if(nnz_threshold == 0.0)
     kgetColRowStats<half, STATS_THREADS, STATS_ITEMS, STATS_ROWS, STATS_THREADS*STATS_ITEMS, 0><<<num_blocks, STATS_THREADS>>>(A, rowStats, colStats, nnz_count_row, nnz_threshold, rows, cols, tiledRows, tiledCols);
   else if(nnz_threshold != 0.0)
@@ -494,13 +495,14 @@ void doubleRowColQuant(half * A, float *rowStats, float *colStats, char *out_col
   int tile_rows = 16;
   int tiledCols = fill_up_to_nearest_multiple(cols, tile_cols);
   int tiledRows = fill_up_to_nearest_multiple(rows, tile_rows);
-  int num_blocks = (tiledCols/tile_cols) * (tiledRows/tile_rows);
-  assert(num_blocks <= 65535 && "CUDA ERROR: Maximum number of blocks for kernel exceeded");
+	int row_tiles = (tiledRows/tile_rows);
+	int col_tiles = (tiledCols/tile_cols);
+	row_tiles = row_tiles > 0 ? row_tiles : 1;
+	col_tiles = col_tiles > 0 ? col_tiles : 1;
+  int num_blocks = row_tiles * col_tiles;
 
-  //cout << cols << " " << tiledCols << " " << tiledRows << endl;
-  //cout << "num blocks " << num_blocks << endl;
+  assert(num_blocks <= 65535 && "CUDA ERROR: Maximum number of blocks for kernel exceeded");
 
-  //cout << A << " " << out_col_normed << endl;
   if(threshold > 0.0f)
     kDoubleRowColQuant<64, 4, 16, 64*4, 1><<<num_blocks, threads>>>(A, rowStats, colStats, out_col_normed, out_row_normed, rowidx, colidx, val, nnz_block_ptr, threshold, rows, cols, tiledCols);
   else
@@ -518,7 +520,12 @@ template <int FORMAT, int TRANSPOSE> void transformRowToFormat(char * A, char *o
   int tile_rows = 32;
   int tiledCols = fill_up_to_nearest_multiple(cols, tile_cols);
   int tiledRows = fill_up_to_nearest_multiple(rows, tile_rows);
-  int num_blocks = (tiledCols/tile_cols) * (tiledRows/tile_rows);
+	int row_tiles = (tiledRows/tile_rows);
+	int col_tiles = (tiledCols/tile_cols);
+	row_tiles = row_tiles > 0 ? row_tiles : 1;
+	col_tiles = col_tiles > 0 ? col_tiles : 1;
+  int num_blocks = row_tiles * col_tiles;
+
   assert(num_blocks <= 65535 && "CUDA ERROR: Maximum number of blocks for kernel exceeded");
   int outCols = fill_up_to_nearest_multiple(cols, 32);
   int outRows = fill_up_to_nearest_multiple(rows, 32);
@@ -545,10 +552,6 @@ template <int FORMAT, int TRANSPOSE> void transformRowToFormat(char * A, char *o
     }
   }
 
-  //cout << cols << " " << tiledCols << " " << tiledRows <<  " " << outCols << endl;
-  //cout << "num blocks " << num_blocks << endl;
-
-  //cout << A << " " << out_col_normed << endl;
   kTransformRowToFormat<256, 8, 32, 32*8, TRANSPOSE, FORMAT><<<num_blocks, threads>>>(A, out, rows, cols, tiledCols, outRows, outCols);
   CUDA_CHECK_RETURN(cudaPeekAtLastError());
 }

tests/test_autograd.py

@@ -23,7 +23,8 @@ str_values = list(product(dim1,dim2,dim3,dim4,str_funcs, dtype, req_grad_str, st
 names = ['dim1_{0}_dim2_{1}_dim3_{2}_dim4_{3}_func_{4}_dtype_{5}_requires_grad_{6}_transpose_{7}'.format(*vals) for vals in str_values]
 @pytest.mark.parametrize("dim1, dim2, dim3, dim4, funcs, dtype, req_grad, transpose", values, ids=names)
 def test_matmul(dim1, dim2, dim3, dim4, funcs, dtype, req_grad, transpose):
-    dim2 = dim2 - (dim2 % 16)
+    if dim2 > 0:
+        dim2 = dim2 - (dim2 % 16)
     dim3 = dim3 - (dim3 % 16)
     dim4 = dim4 - (dim4 % 16)
     for i in range(k):
@@ -179,6 +180,7 @@ dim2 = torch.randint(32,96, size=(n,)).tolist()
 dim3 = torch.randint(32,96, size=(n,)).tolist()
 dim4 = torch.randint(32,96, size=(n,)).tolist()
 
+dim2.append(0)
 #dim1 = (17,)
 #dim2 = (7,)
 #dim3 = (37,)
@@ -234,9 +236,9 @@ def test_matmullt(dim1, dim2, dim3, dim4, funcs, dtype, req_grad, transpose, dec
             err = torch.abs(out_bnb-out_torch).mean().item()
             #print(f'abs error {err:.4f}')
             idx = torch.isclose(out_bnb, out_torch, atol=0.01, rtol=0.1)
-            assert (idx==0).sum().item() < n*0.0175
+            assert (idx==0).sum().item() <= n*0.0175
             idx = torch.isclose(out_bnb, out_torch, atol=0.035, rtol=0.2)
-            assert (idx==0).sum().item() < n*0.001
+            assert (idx==0).sum().item() <= n*0.001
 
             if has_fp16_weights:
                 if any(req_grad):
@@ -260,11 +262,15 @@ def test_matmullt(dim1, dim2, dim3, dim4, funcs, dtype, req_grad, transpose, dec
                     torch.testing.assert_allclose(gradA1, gradA2, atol=0.015, rtol=0.1)
                 if req_grad[1]:
                     n = gradB1.numel()
-                    assert torch.abs(gradB1).sum() > 0.0
-                    assert torch.abs(gradB2).sum() > 0.0
+                    if dim2 > 0:
+                        assert torch.abs(gradB1).sum() > 0.0
+                        assert torch.abs(gradB2).sum() > 0.0
+                    else:
+                        assert torch.abs(gradB1).sum() == 0.0
+                        assert torch.abs(gradB2).sum() == 0.0
                     idx = torch.isclose(gradB1, gradB2, atol=0.06, rtol=0.3)
-                    assert (idx==0).sum().item() < n*0.1
+                    assert (idx==0).sum().item() <= n*0.1
                     idx = torch.isclose(gradB1, gradB2, atol=0.10, rtol=0.3)
-                    assert (idx==0).sum().item() < n*0.02
+                    assert (idx==0).sum().item() <= n*0.02
                     torch.testing.assert_allclose(gradB1, gradB2, atol=0.18, rtol=0.3)