Conda: Enable use of mingw-w64 g++ and mkl when not on PATH

theano/compat/__init__.py

@@ -107,3 +107,30 @@ class DefaultOrderedDict(OrderedDict):
         return type(self)(self.default_factory, self)
 
 __all__ += ['DefaultOrderedDict']
+
+
+def maybe_add_to_os_environ_pathlist(var, newpath):
+    '''Unfortunately, Conda offers to make itself the default Python
+       and those who use it that way will probably not activate envs
+       correctly meaning e.g. mingw-w64 g++ may not be on their PATH.
+
+       This function ensures that, if `newpath` is an absolute path,
+       and it is not already in os.environ[var] it gets added to the
+       front.
+
+       The reason we check first is because Windows environment vars
+       are limited to 8191 characters and it is easy to hit that.
+
+       `var` will typically be 'PATH'. '''
+
+    import os
+    if os.path.isabs(newpath):
+        try:
+            oldpaths = os.environ[var].split(os.pathsep)
+            if newpath not in oldpaths:
+                newpaths = os.pathsep.join([newpath] + oldpaths)
+                os.environ[var] = newpaths
+        except:
+            pass
+
+__all__ += ['maybe_add_to_os_environ_pathlist']

theano/configdefaults.py

@@ -19,6 +19,7 @@ from theano.configparser import (AddConfigVar, BoolParam, ConfigParam, EnumStr,
                                  TheanoConfigParser, THEANO_FLAGS_DICT)
 from theano.misc.cpucount import cpuCount
 from theano.misc.windows import call_subprocess_Popen, output_subprocess_Popen
+from theano.compat import maybe_add_to_os_environ_pathlist
 
 
 _logger = logging.getLogger('theano.configdefaults')
@@ -418,6 +419,19 @@ try:
 except OSError:
     rc = 1
 
+# Anaconda on Windows has mingw-w64 packages including GCC, but it may not be on PATH.
+if rc != 0:
+    if sys.platform == "win32":
+        mingw_w64_gcc = os.path.join(os.path.dirname(sys.executable), "Library", "mingw-w64", "bin", "g++")
+        try:
+            rc = call_subprocess_Popen([mingw_w64_gcc, '-v'])
+            if rc == 0:
+                maybe_add_to_os_environ_pathlist('PATH', os.path.dirname(mingw_w64_gcc))
+        except OSError:
+            rc = 1
+        if rc != 0:
+            _logger.warning("conda g++ not available, use `conda install m2w64-toolchain`")
+
 if rc != 0:
     param = ""
 
@@ -1269,6 +1283,7 @@ def default_blas_ldflags():
                               blas_info.get('library_dirs', [])])
                 res = try_blas_flag(flags)
                 if res:
+                    maybe_add_to_os_environ_pathlist('PATH', lib_path)
                     return res
 
         # to support path that includes spaces, we need to wrap it with double quotes on Windows