Fix blas C code having wrong alpha and beta for float16.

theano/gpuarray/blas.py

@@ -47,8 +47,8 @@ class GpuGemv(BlasOp):
         A = as_gpuarray_variable(A, ctx_name)
         x = as_gpuarray_variable(x, ctx_name)
         y = as_gpuarray_variable(y, ctx_name)
-        alpha = as_tensor_variable(alpha)
-        beta = as_tensor_variable(beta)
+        alpha = as_tensor_variable(alpha).astype('float64')
+        beta = as_tensor_variable(beta).astype('float64')
         assert alpha.ndim == 0
         assert beta.ndim == 0
         assert A.ndim == 2
@@ -128,8 +128,8 @@ class GpuGemm(BlasOp):
         A = as_gpuarray_variable(A, ctx_name)
         B = as_gpuarray_variable(B, ctx_name)
         C = as_gpuarray_variable(C, ctx_name)
-        alpha = as_tensor_variable(alpha)
-        beta = as_tensor_variable(beta)
+        alpha = as_tensor_variable(alpha).astype('float64')
+        beta = as_tensor_variable(beta).astype('float64')
         assert alpha.ndim == 0
         assert beta.ndim == 0
         assert A.ndim == 2
@@ -208,7 +208,7 @@ class GpuGer(BlasOp):
         A = as_gpuarray_variable(A, ctx_name)
         x = as_gpuarray_variable(x, ctx_name)
         y = as_gpuarray_variable(y, ctx_name)
-        alpha = as_tensor_variable(alpha)
+        alpha = as_tensor_variable(alpha).astype('float64')
         assert alpha.ndim == 0
         assert A.ndim == 2
         assert x.ndim == 1
@@ -345,8 +345,8 @@ class GpuGemmBatch(BlasOp):
         A = as_gpuarray_variable(A, ctx_name)
         B = as_gpuarray_variable(B, ctx_name)
         C = as_gpuarray_variable(C, ctx_name)
-        alpha = as_tensor_variable(alpha)
-        beta = as_tensor_variable(beta)
+        alpha = as_tensor_variable(alpha).astype('float64')
+        beta = as_tensor_variable(beta).astype('float64')
         assert alpha.ndim == 0
         assert beta.ndim == 0
         assert A.ndim == 3