fix fp16 grid_size for size=1; test=release/1.6 (#20806)

paddle/fluid/operators/elementwise/elementwise_add_op.cu

@@ -40,8 +40,9 @@ struct SameDimsElemwiseAdd<platform::CUDADeviceContext, platform::float16> {
                   const framework::Tensor* x, const framework::Tensor* y,
                   framework::Tensor* z) {
     auto size = x->numel();
-    dim3 gird_size = dim3(
-        (size / 2 + PADDLE_CUDA_THREAD_SIZE - 1) / PADDLE_CUDA_THREAD_SIZE, 1);
+    dim3 gird_size = dim3(((size + 1) / 2 + PADDLE_CUDA_THREAD_SIZE - 1) /
+                              PADDLE_CUDA_THREAD_SIZE,
+                          1);
     dim3 block_size = dim3(PADDLE_CUDA_THREAD_SIZE, 1);
     const half* x2 =
         reinterpret_cast<const half*>(x->data<platform::float16>());

paddle/fluid/operators/elementwise/elementwise_div_op.cu

@@ -41,8 +41,9 @@ struct SameDimsElemwiseDiv<platform::CUDADeviceContext, platform::float16> {
                   const framework::Tensor* x, const framework::Tensor* y,
                   framework::Tensor* z) {
     auto size = x->numel();
-    dim3 gird_size = dim3(
-        (size / 2 + PADDLE_CUDA_THREAD_SIZE - 1) / PADDLE_CUDA_THREAD_SIZE, 1);
+    dim3 gird_size = dim3(((size + 1) / 2 + PADDLE_CUDA_THREAD_SIZE - 1) /
+                              PADDLE_CUDA_THREAD_SIZE,
+                          1);
     dim3 block_size = dim3(PADDLE_CUDA_THREAD_SIZE, 1);
     const half* x2 =
         reinterpret_cast<const half*>(x->data<platform::float16>());

paddle/fluid/operators/elementwise/elementwise_mul_op.cu

@@ -41,8 +41,9 @@ struct SameDimsElemwiseMul<platform::CUDADeviceContext, platform::float16> {
                   const framework::Tensor* x, const framework::Tensor* y,
                   framework::Tensor* z) {
     auto size = x->numel();
-    dim3 gird_size = dim3(
-        (size / 2 + PADDLE_CUDA_THREAD_SIZE - 1) / PADDLE_CUDA_THREAD_SIZE, 1);
+    dim3 gird_size = dim3(((size + 1) / 2 + PADDLE_CUDA_THREAD_SIZE - 1) /
+                              PADDLE_CUDA_THREAD_SIZE,
+                          1);
     dim3 block_size = dim3(PADDLE_CUDA_THREAD_SIZE, 1);
     const half* x2 =
         reinterpret_cast<const half*>(x->data<platform::float16>());

paddle/fluid/operators/elementwise/elementwise_sub_op.cu

@@ -41,8 +41,9 @@ struct SameDimsElemwiseSub<platform::CUDADeviceContext, platform::float16> {
                   const framework::Tensor* x, const framework::Tensor* y,
                   framework::Tensor* z) {
     auto size = x->numel();
-    dim3 gird_size = dim3(
-        (size / 2 + PADDLE_CUDA_THREAD_SIZE - 1) / PADDLE_CUDA_THREAD_SIZE, 1);
+    dim3 gird_size = dim3(((size + 1) / 2 + PADDLE_CUDA_THREAD_SIZE - 1) /
+                              PADDLE_CUDA_THREAD_SIZE,
+                          1);
     dim3 block_size = dim3(PADDLE_CUDA_THREAD_SIZE, 1);
     const half* x2 =
         reinterpret_cast<const half*>(x->data<platform::float16>());