Add unit test

theano/sandbox/test_rng_mrg.py

@@ -17,6 +17,7 @@ import unittest
 from theano.tests import unittest_tools as utt
 from nose.plugins.skip import SkipTest
 from nose.plugins.attrib import attr
+from nose.tools import assert_raises
 
 #TODO: test gpu
 # Done in test_consistency_GPU_{serial,parallel}
@@ -305,6 +306,22 @@ def test_consistency_GPU_parallel():
     samples = numpy.array(samples).flatten()
     assert(numpy.allclose(samples, java_samples))
 
+def test_GPU_nstreams_limit():
+    """Verify that a ValueError is raised when n_streams
+    is greater than 2**20 on GPU. This is the value of
+    (NUM_VECTOR_OP_THREADS_PER_BLOCK * NUM_VECTOR_OP_BLOCKS).
+    """
+    if not cuda_available:
+        raise SkipTest('Optional package cuda not available')
+
+    seed = 12345
+    R = MRG_RandomStreams(seed=seed, use_cuda=True)
+    
+    def eval_uniform(size, nstreams):
+        return R.uniform(size=size, nstreams=nstreams).eval()
+    
+    eval_uniform((10,), 2**20)
+    assert_raises(ValueError, eval_uniform, (10,), 2**20 + 1)
 
 def test_consistency_GPUA_serial():
     '''Verify that the random numbers generated by GPUA_mrg_uniform, serially,