small optimization to GpuSum

theano/sandbox/cuda/basic_ops.py

@@ -636,7 +636,20 @@ class GpuSum(Op):
             }
             buf[threadNum] = mysum;
             // no sync because only one warp is running
-            if (threadNum < 16)
+            if(threadCount >32)
+            {
+                buf[threadNum] += buf[threadNum+16];
+                buf[threadNum] += buf[threadNum+8];
+                buf[threadNum] += buf[threadNum+4];
+                buf[threadNum] += buf[threadNum+2];
+                buf[threadNum] += buf[threadNum+1];
+                if (threadNum == 0)
+                {
+                    %(z_pos)s = buf[0];
+                }
+
+            }
+            else if (threadNum < 16)
             {
                 //reduce so that threadNum 0 has the sum of everything
                 if(threadNum + 16 < threadCount) buf[threadNum] += buf[threadNum+16];
@@ -979,7 +992,7 @@ class GpuSum(Op):
 
     def c_code_cache_version(self):
         #return ()
-        return (9,)
+        return (10,)
 
 
     def c_support_code_apply(self, node, nodename):

theano/sandbox/cuda/tests/test_basic_ops.py

@@ -36,7 +36,7 @@ def test_sum():
     """
 
     for shape, pattern in [((5,),[0]),
-                           ((5,4),[0,1]),((5,4),[0]),
+                           ((5,4),[0,1]),((33,31),[0,1]),((5,4),[0]),#need something bigger then 32 for some opt test.
                            ((5,4,3),[0]),((5,4,3),[0,1]),((5,4,3),[2]),((5,4,3),[0,1,2]),
                            ((5,4,3,2),[0,1,2,3]), ((5,4,3,2),[0,2,3])]:
         a = tensor.TensorType('float32',(False,)*len(shape))()