fix SplitLodTensor when batch_size = 0, test=develop (#19866)

paddle/fluid/framework/lod_tensor.cc

@@ -283,6 +283,21 @@ std::vector<LoDTensor> LoDTensor::SplitLoDTensor(
   std::vector<LoDTensor> results;
   results.reserve(result_size);
 
+  // if result_size(batch_size) is 0, just return #places.size() copys of empty
+  // tensors.
+  if (result_size == 0) {
+    for (size_t i = 0; i < places.size(); ++i) {
+      LoDTensor dst;
+      dst.Resize(dims());
+      dst.mutable_data(places[i], type());
+      if (!lod().empty()) {
+        dst.set_lod(lod());
+      }
+      results.emplace_back(dst);
+    }
+    return results;
+  }
+
   int step_width = static_cast<int>(batch_size / result_size);
   for (size_t i = 0; i < result_size; ++i) {
     int begin = static_cast<int>(i * step_width);

paddle/fluid/framework/lod_tensor_test.cc

@@ -155,6 +155,26 @@ TEST(LoD, SplitLoDTensor) {
   EXPECT_EQ(lods[1].lod(), lod1);
 }
 
+TEST(LoD, SplitLoDTensorWithZeroBatchSize) {
+  LoD lod;
+  lod.push_back(std::vector<size_t>({0}));
+
+  platform::CPUPlace place;
+  LoDTensor lod_tensor;
+  lod_tensor.Resize({0, 5});
+  lod_tensor.mutable_data<float>(place);
+  lod_tensor.set_lod(lod);
+
+  std::vector<platform::Place> places{platform::CPUPlace(),
+                                      platform::CPUPlace()};
+  LoD lod_res;
+  lod_res.push_back(std::vector<size_t>({0}));
+
+  auto lods = lod_tensor.SplitLoDTensor(places);
+  EXPECT_EQ(lods[0].lod(), lod_res);
+  EXPECT_EQ(lods[1].lod(), lod_res);
+}
+
 TEST(LoD, MergeLoDTensor) {
   LoD lod;
   lod.push_back(std::vector<size_t>({0, 2, 4, 5, 6}));