Fix copy wrong pos bug

test=develop

Author: velconia

paddle/fluid/operators/math/sequence_pooling.cc

@@ -242,7 +242,7 @@ class SequencePoolGradFunctor<platform::CPUDeviceContext, T> {
       auto blas = math::GetBlas<platform::CPUDeviceContext, T>(context);
       for (int i = 0; i < static_cast<int>(lod.size()) - 1; ++i) {
         int64_t h = static_cast<int64_t>(lod[i + 1] - lod[i]);
-        int64_t in_offset = lod[i];
+        int64_t in_offset = lod[i] * in_w;
         const T* out_pos = out_g_data + i * out_w;
         T* in_pos = in_g_data + in_offset;
         for (int r = 0; r != h; ++r) {

paddle/fluid/operators/math/sequence_pooling_test.cc

@@ -70,7 +70,7 @@ void TestSequencePoolingSum(const paddle::framework::LoD& lod) {
   EXPECT_EQ(in_grad.lod(), lod);
 
   if (paddle::platform::is_cpu_place(*place)) {
-    for (int64_t i = 0; i < cpu_in_grad.lod()[0].size() - 1; ++i) {
+    for (int64_t i = 0; i < in_grad.lod()[0].size() - 1; ++i) {
       int64_t begin = in_grad.lod()[0][i];
       int64_t end = in_grad.lod()[0][i + 1];
       paddle::framework::Tensor tmp = in_grad.Slice(begin, end);