Sync the timming when using the GPU. Otherwise, we end up with 0s!

theano/misc/check_blas.py

@@ -90,9 +90,14 @@ def execute(execute=True, verbose=True, M=2000, N=2000, K=2000,
     t1 = -1
 
     if execute:
+        sync = (hasattr(theano, "sandbox") and
+                hasattr(theano.sandbox, "cuda") and
+                theano.sandbox.cuda.cuda_available)
         t0 = time.time()
         for i in range(iters):
             f()
+        if sync:
+            theano.sandbox.cuda.synchronize()
         t1 = time.time()
     return t1 - t0, impl