Reverting setup.py to rely on cpp_extension's native CUDA_HOME, because...

Reverting setup.py to rely on cpp_extension's native CUDA_HOME, because upstream fixed cross-compilation

setup.py

@@ -4,7 +4,7 @@ import re
 import subprocess
 from setuptools import setup, find_packages
 from distutils.command.clean import clean
-from torch.utils.cpp_extension import CUDAExtension
+from torch.utils.cpp_extension import CUDAExtension, CUDA_HOME
 
 # TODO:  multiple modules, so we don't have to route all interfaces through
 # the same interface.cpp file?
@@ -36,48 +36,6 @@ def find(path, regex_func, collect=False):
                     return os.path.join(root, file)
     return list(set(collection))
 
-# The means of finding CUDA_HOME in cpp_extension does not allow cross-compilation 
-# if torch.cuda.is_available() is False.
-def find_cuda_home():
-    cuda_path = None
-    CUDA_HOME = None
-
-    CUDA_HOME = os.getenv('CUDA_HOME', '/usr/local/cuda')
-    if not os.path.exists(CUDA_HOME):
-        # We use nvcc path on Linux and cudart path on macOS
-        cudart_path = ctypes.util.find_library('cudart')
-        if cudart_path is not None:
-            cuda_path = os.path.dirname(cudart_path)
-        if cuda_path is not None:
-            CUDA_HOME = os.path.dirname(cuda_path)
-            
-    if not cuda_path and not CUDA_HOME:
-        nvcc_path = find('/usr/local/', re.compile("nvcc").search, False)
-        if nvcc_path:
-            CUDA_HOME = os.path.dirname(nvcc_path)
-            if CUDA_HOME:
-                os.path.dirname(CUDA_HOME)
-
-        if (not os.path.exists(CUDA_HOME+os.sep+"lib64")
-            or not os.path.exists(CUDA_HOME+os.sep+"include") ):
-            raise RuntimeError("Error: found NVCC at ", 
-                               nvcc_path,
-                               " but could not locate CUDA libraries"+
-                               " or include directories.")
-        
-        raise RuntimeError("Error: Could not find cuda on this system. " +
-                            "Please set your CUDA_HOME enviornment variable "
-                            "to the CUDA base directory.")
-
-    print("Found CUDA_HOME = ", CUDA_HOME)
-
-    return CUDA_HOME
-
-CUDA_HOME = find_cuda_home()
-
-# Patch the extension's view of CUDA_HOME to allow cross-compilation
-torch.utils.cpp_extension.CUDA_HOME = CUDA_HOME
-
 def get_cuda_version():
     NVCC = find(CUDA_HOME+os.sep+"bin",
                 re.compile('nvcc$').search)
@@ -96,27 +54,32 @@ def get_cuda_version():
 
     return CUDA_MAJOR
 
-CUDA_MAJOR = get_cuda_version()
-
-gencodes = ['-gencode', 'arch=compute_52,code=sm_52',
-            '-gencode', 'arch=compute_60,code=sm_60',
-            '-gencode', 'arch=compute_61,code=sm_61',]
-
-if CUDA_MAJOR > 8:
-    gencodes += ['-gencode', 'arch=compute_70,code=sm_70',
-                 '-gencode', 'arch=compute_70,code=compute_70',]
-
-ext_modules = []
-extension = CUDAExtension(
-    'apex_C', [
-        'csrc/interface.cpp',
-        'csrc/weight_norm_fwd_cuda.cu',
-        'csrc/weight_norm_bwd_cuda.cu',
-        'csrc/scale_cuda.cu',
-    ],
-    extra_compile_args={'cxx': ['-g'] + version_le_04,
-                        'nvcc': ['-O3'] + version_le_04 + gencodes})
-ext_modules.append(extension)
+if CUDA_HOME is not None:
+    print("Found CUDA_HOME = ", CUDA_HOME)
+
+    CUDA_MAJOR = get_cuda_version()
+
+    gencodes = ['-gencode', 'arch=compute_52,code=sm_52',
+                '-gencode', 'arch=compute_60,code=sm_60',
+                '-gencode', 'arch=compute_61,code=sm_61',]
+
+    if CUDA_MAJOR > 8:
+        gencodes += ['-gencode', 'arch=compute_70,code=sm_70',
+                     '-gencode', 'arch=compute_70,code=compute_70',]
+
+    ext_modules = []
+    extension = CUDAExtension(
+        'apex_C', [
+            'csrc/interface.cpp',
+            'csrc/weight_norm_fwd_cuda.cu',
+            'csrc/weight_norm_bwd_cuda.cu',
+            'csrc/scale_cuda.cu',
+        ],
+        extra_compile_args={'cxx': ['-g'] + version_le_04,
+                            'nvcc': ['-O3'] + version_le_04 + gencodes})
+    ext_modules.append(extension)
+else:
+    raise RuntimeError("Could not find Cuda install directory")
 
 setup(
     name='apex',