metis support optional

README.md

@@ -59,7 +59,8 @@ $ echo $CPATH
 >>> /usr/local/cuda/include:...
 ```
 
-Afterwards, download and install the [METIS library](http://glaros.dtc.umn.edu/gkhome/metis/metis/download) by following the instructions in the `Install.txt` file.
+If you want to additionally build `torch-sparse` with METIS support, *e.g.* for partioning, please download and install the [METIS library](http://glaros.dtc.umn.edu/gkhome/metis/metis/download) by following the instructions in the `Install.txt` file.
+Afterwards, set the environment variable `WITH_METIS=1`.
 
 Then run:
 
@@ -67,11 +68,11 @@ Then run:
 pip install torch-scatter torch-sparse
 ```
 
-When running in a docker container without nvidia driver, PyTorch needs to evaluate the compute capabilities and may fail.
+When running in a docker container without NVIDIA driver, PyTorch needs to evaluate the compute capabilities and may fail.
 In this case, ensure that the compute capabilities are set via `TORCH_CUDA_ARCH_LIST`, *e.g.*:
 
 ```
-export TORCH_CUDA_ARCH_LIST = "6.0 6.1 7.2+PTX 7.5+PTX"
+export TORCH_CUDA_ARCH_LIST="6.0 6.1 7.2+PTX 7.5+PTX"
 ```
 
 ## Functions

csrc/cpu/metis_cpu.cpp

 #include "metis_cpu.h"
 
+#ifdef WITH_METIS
 #include <metis.h>
+#endif
 
 #include "utils.h"
 
 torch::Tensor partition_cpu(torch::Tensor rowptr, torch::Tensor col,
                             int64_t num_parts, bool recursive) {
+#ifdef WITH_METIS
   CHECK_CPU(rowptr);
   CHECK_CPU(col);
 
   int64_t nvtxs = rowptr.numel() - 1;
+  auto part = torch::empty(nvtxs, rowptr.options());
+
   auto *xadj = rowptr.data_ptr<int64_t>();
   auto *adjncy = col.data_ptr<int64_t>();
   int64_t ncon = 1;
   int64_t objval = -1;
-  auto part = torch::empty(nvtxs, rowptr.options());
   auto part_data = part.data_ptr<int64_t>();
 
   if (recursive) {
@@ -26,4 +30,7 @@ torch::Tensor partition_cpu(torch::Tensor rowptr, torch::Tensor col,
   }
 
   return part;
+#else
+  AT_ERROR("Not compiled with METIS support");
+#endif
 }

csrc/metis.cpp

@@ -3,10 +3,8 @@
 
 #include "cpu/metis_cpu.h"
 
-#include <metis.h>
-
 #ifdef _WIN32
-PyMODINIT_FUNC PyInit__metis_wrapper(void) { return NULL; }
+PyMODINIT_FUNC PyInit__metis(void) { return NULL; }
 #endif
 
 torch::Tensor partition(torch::Tensor rowptr, torch::Tensor col,

script/metis.sh

 #!/bin/bash
 
 METIS=metis-5.1.0
+export WITH_METIS=1
 
 wget -nv http://glaros.dtc.umn.edu/gkhome/fetch/sw/metis/${METIS}.tar.gz
 tar -xvzf ${METIS}.tar.gz

setup.py

@@ -16,10 +16,18 @@ if os.getenv('FORCE_CPU', '0') == '1':
 
 BUILD_DOCS = os.getenv('BUILD_DOCS', '0') == '1'
 
+WITH_METIS = False
+if os.getenv('WITH_METIS', '0') == '1':
+    WITH_METIS = True
+
 
 def get_extensions():
     Extension = CppExtension
     define_macros = []
+    libraries = []
+    if WITH_METIS:
+        define_macros += [('WITH_METIS', None)]
+        libraries += ['metis']
     extra_compile_args = {'cxx': []}
     extra_link_args = []
 
@@ -59,7 +67,7 @@ def get_extensions():
             define_macros=define_macros,
             extra_compile_args=extra_compile_args,
             extra_link_args=extra_link_args,
-            libraries=['metis'],
+            libraries=libraries,
         )
         extensions += [extension]