Merge pull request #1228 from lamblin/default_blas_flags

theano/gof/cmodule.py

@@ -1483,6 +1483,49 @@ class GCC_compiler(object):
             cxxflags.append("-D NPY_ARRAY_F_CONTIGUOUS=NPY_F_CONTIGUOUS")
         return cxxflags
 
+    @staticmethod
+    def try_flags(flag_list):
+        '''
+        Try to compile a dummy file with these flags.
+
+        Returns True if compilation was successful, False if there
+        were errors.
+        '''
+        if not theano.config.cxx:
+            return False
+
+        rval = True
+        try:
+            code = """
+            int main(int argc, char** argv)
+            {
+                return 0;
+            }
+            """
+            fd, path = tempfile.mkstemp(suffix='.c', prefix='try_flags_')
+            dummy_stdin = open(os.devnull)
+            try:
+                os.write(fd, code)
+                os.close(fd)
+                fd = None
+                proc = call_subprocess_Popen(['g++', path] + flag_list,
+                        stdout=subprocess.PIPE,
+                        stderr=subprocess.PIPE,
+                        stdin=dummy_stdin.fileno())
+                proc.wait()
+                if proc.returncode != 0:
+                    rval = False
+            finally:
+                del dummy_stdin
+                try:
+                    if fd is not None:
+                        os.close(fd)
+                finally:
+                    os.remove(path)
+        except OSError, e:
+            rval = False
+        return rval
+
     @staticmethod
     def compile_str(module_name, src_code, location=None,
                     include_dirs=None, lib_dirs=None, libs=None,

theano/tensor/blas.py

@@ -138,6 +138,7 @@ from theano.gof import (utils, Op, view_roots, DestroyHandler,
                         InconsistencyError, toolbox, SequenceDB,
                         EquilibriumOptimizer, Apply,
                         ReplacementDidntRemovedError)
+from theano.gof.cmodule import GCC_compiler
 from theano.printing import pprint, FunctionPrinter, debugprint
 from theano.compile.mode import optdb
 from theano.gof.python25 import all, any
@@ -373,9 +374,8 @@ def default_blas_ldflags():
 
         #if numpy was linked with library that are not installed, we
         #can't reuse them.
-        if all(not os.path.exists(dir) for dir in blas_info['library_dirs']):
-            return "-lblas"
-        return ' '.join(
+        if any(os.path.exists(dir) for dir in blas_info['library_dirs']):
+            return ' '.join(
                         #TODO: the Gemm op below should separate the
                         # -L and -l arguments into the two callbacks
                         # that CLinker uses for that stuff.  for now,
@@ -386,7 +386,17 @@ def default_blas_ldflags():
                         [])
 #                       ['-I%s' % l for l in blas_info['include_dirs']])
     except KeyError:
+        pass
+
+    # Even if we could not detect what was used for numpy, or if these
+    # libraries are not found, most Linux systems have a libblas.so
+    # readily available. We try to see if that's the case, rather
+    # than disable blas.
+    if GCC_compiler.try_flags(["-lblas"]):
         return "-lblas"
+    else:
+        return ""
+
 
 AddConfigVar('blas.ldflags',
         "lib[s] to include for [Fortran] level-3 blas implementation",