Speed up choice with replace on the GPU.

theano/gpuarray/multinomial.py

@@ -392,9 +392,12 @@ KERNEL void k_multi_warp_multinomial_wor(
         PyErr_Format(PyExc_ValueError, "unis.shape[0] != pvals.shape[0] * n");
         %(fail)s
     }
-
-    pvals_copy = pygpu_copy(pvals, GA_C_ORDER);
-
+    if (! %(replace)s) {
+        pvals_copy = pygpu_copy(pvals, GA_C_ORDER);
+    } else {
+        pvals_copy = pvals;
+        Py_INCREF(pvals_copy);
+    }
     dims[0] = n_samples;
     dims[1] = PyGpuArray_DIMS(pvals)[0];
 
@@ -474,7 +477,7 @@ KERNEL void k_multi_warp_multinomial_wor(
         return s
 
     def c_code_cache_version(self):
-        return (6,)
+        return (7,)
 
 
 @register_opt('fast_compile')