Make parent_idx a dispensable output for beam_search op to support models saved by older paddle version. (#16106)

test=develop

paddle/fluid/operators/beam_search_op.cc

@@ -51,9 +51,9 @@ class BeamSearchOpMaker : public framework::OpProtoAndCheckerMaker {
     AddOutput("selected_scores",
               "A LoDTensor containing the accumulated scores corresponding to "
               "Output(selected_ids).");
-    AddOutput(
-        "parent_idx",
-        "A Tensor preserving the selected_ids' parent indice in pre_ids.");
+    AddOutput("parent_idx",
+              "A Tensor preserving the selected_ids' parent indice in pre_ids.")
+        .AsDispensable();
 
     // Attributes stored in AttributeMap
     AddAttr<int>("level", "the level of LoDTensor");

paddle/fluid/operators/beam_search_op.h

@@ -44,7 +44,6 @@ class BeamSearchOpKernel : public framework::OpKernel<T> {
     auto* parent_idx = context.Output<framework::Tensor>("parent_idx");
     PADDLE_ENFORCE_NOT_NULL(selected_ids);
     PADDLE_ENFORCE_NOT_NULL(selected_scores);
-    PADDLE_ENFORCE_NOT_NULL(parent_idx);
 
     math::BeamSearchFunctor<DeviceContext, T> alg;
     alg(context.template device_context<DeviceContext>(), pre_ids, pre_scores,

paddle/fluid/operators/math/beam_search.cc

@@ -56,15 +56,15 @@ class BeamSearchFunctor<platform::CPUDeviceContext, T> {
     // the output tensor shape should be [num_instances, 1]
     auto dims = framework::make_ddim(
         std::vector<int64_t>({static_cast<int>(num_instances), 1}));
-    selected_ids->Resize(dims);
-    selected_scores->Resize(dims);
-    parent_idx->Resize({static_cast<int64_t>(num_instances)});
-
     auto *selected_ids_data =
-        selected_ids->mutable_data<int64_t>(platform::CPUPlace());
+        selected_ids->mutable_data<int64_t>(dims, platform::CPUPlace());
     auto *selected_scores_data =
-        selected_scores->mutable_data<float>(platform::CPUPlace());
-    auto *parent_idx_data = parent_idx->mutable_data<int>(platform::CPUPlace());
+        selected_scores->mutable_data<float>(dims, platform::CPUPlace());
+    auto *parent_idx_data =
+        parent_idx
+            ? parent_idx->mutable_data<int>(
+                  {static_cast<int64_t>(num_instances)}, platform::CPUPlace())
+            : nullptr;
 
     // fill in data
     std::vector<size_t> low_level;
@@ -72,7 +72,9 @@ class BeamSearchFunctor<platform::CPUDeviceContext, T> {
     for (auto &items : selected_items) {
       low_level.push_back(low_offset);
       for (auto &item : items) {
-        parent_idx_data[low_offset] = static_cast<int>(low_level.size() - 1);
+        if (parent_idx) {
+          parent_idx_data[low_offset] = static_cast<int>(low_level.size() - 1);
+        }
         selected_ids_data[low_offset] = item.id;
         selected_scores_data[low_offset] = item.score;
         low_offset++;

paddle/fluid/operators/math/beam_search.cu

@@ -168,6 +168,7 @@ __device__ __forceinline__ bool PruneEndBeams(Triple* top_beam_local,
   return finish_flag;
 }
 
+template <bool ReturnParentIdx = false>
 __device__ __forceinline__ void WriteBack(
     int64_t* selected_ids, float* selected_scores, int* parent_idx,
     size_t* selected_offsets, Triple* top_beam_local,
@@ -183,7 +184,9 @@ __device__ __forceinline__ void WriteBack(
         selected_ids[global_index] =
             static_cast<int64_t>(top_beam_local[local_index].id);
         selected_scores[global_index] = top_beam_local[local_index].score;
-        parent_idx[global_index] = static_cast<int>(global_offset);
+        if (ReturnParentIdx) {
+          parent_idx[global_index] = static_cast<int>(global_offset);
+        }
         global_index++;
       }
     }
@@ -241,9 +244,15 @@ __device__ void BeamSearchDetails(
       selected_offsets[0] = 0;
     }
 
-    WriteBack(selected_ids, selected_scores, parent_idx, selected_offsets,
-              top_beam_local, seq_offset_start, seq_offset_end,
-              selected_seq_start, selected_seq_length);
+    if (parent_idx) {
+      WriteBack<true>(selected_ids, selected_scores, parent_idx,
+                      selected_offsets, top_beam_local, seq_offset_start,
+                      seq_offset_end, selected_seq_start, selected_seq_length);
+    } else {
+      WriteBack<false>(selected_ids, selected_scores, parent_idx,
+                       selected_offsets, top_beam_local, seq_offset_start,
+                       seq_offset_end, selected_seq_start, selected_seq_length);
+    }
   }
 }
 
@@ -337,8 +346,12 @@ class BeamSearchFunctor<platform::CUDADeviceContext, T> {
         selected_ids->mutable_data<int64_t>(selected_dims, context.GetPlace());
     float* selected_scores_data =
         selected_scores->mutable_data<float>(selected_dims, context.GetPlace());
-    int* parent_idx_data = parent_idx->mutable_data<int>(
-        {static_cast<int64_t>(num_seqs * beam_size)}, context.GetPlace());
+    int* parent_idx_data =
+        parent_idx
+            ? parent_idx->mutable_data<int>(
+                  {static_cast<int64_t>(num_seqs * beam_size)},
+                  context.GetPlace())
+            : nullptr;
 
     framework::LoD selected_lod(2);
     selected_lod[0].assign(abs_lod[level].begin(), abs_lod[level].end());
@@ -396,7 +409,9 @@ class BeamSearchFunctor<platform::CUDADeviceContext, T> {
           {static_cast<int64_t>(selected_lod[1].back()), 1});
       selected_ids->Resize(final_selected_dims);
       selected_scores->Resize(final_selected_dims);
-      parent_idx->Resize({static_cast<int64_t>(selected_lod[1].back())});
+      if (parent_idx) {
+        parent_idx->Resize({static_cast<int64_t>(selected_lod[1].back())});
+      }
     }
   }
 };