follow comment and fix typo

test=develop

paddle/fluid/framework/ir/seqpool_concat_fuse_pass.cc

@@ -39,21 +39,25 @@ PDNode* BuildSeqPoolConcatPattern(PDPattern* pattern,
 
   auto is_seqpool_op_with_pootype_of_nth_input_of_concat = [=](
       Node* x, const std::string& type, int idx) -> bool {
-    bool ok = x && x->IsOp() && x->Op()->Type() == "sequence_pool" &&
+    bool this_is_seqpool_op =
+        x && x->IsOp() && x->Op()->Type() == "sequence_pool" &&
         x->Op()->HasAttr("pooltype") &&
         boost::get<std::string>(x->Op()->GetAttr("pooltype")) == type &&
         x->outputs.size() == 2;  // seqpool should only have 2 outputs
-    if (ok) {
-      // only one output of seqpool_op is nth_input_var of concat
-      // the other one should be unused empty var
+    bool satisfied_all = this_is_seqpool_op;
+    if (this_is_seqpool_op) {
+      // Only one output of seqpool_op is nth_input_var of concat,
+      // the other one should be unused empty var.
       if (is_nth_input_var_of_concat(x->outputs[0], idx)) {
-        ok = ok && x->outputs[1]->IsVar() && x->outputs[1]->outputs.size() == 0;
+        satisfied_all = satisfied_all && x->outputs[1]->IsVar() &&
+                        x->outputs[1]->outputs.size() == 0;
       } else {
-        ok = ok && is_nth_input_var_of_concat(x->outputs[1], idx) &&
+        satisfied_all =
+            satisfied_all && is_nth_input_var_of_concat(x->outputs[1], idx) &&
             x->outputs[0]->IsVar() && x->outputs[0]->outputs.size() == 0;
       }
     }
-    return ok;
+    return satisfied_all;
   };
 
   auto* concat_op = pattern->NewNode(

paddle/fluid/framework/ir/seqpool_concat_fuse_pass.h

@@ -23,6 +23,20 @@ namespace paddle {
 namespace framework {
 namespace ir {
 
+/**
+ * Fuse SequencePool(with sum pooltype yet) and Concat;
+ *
+ * Before fuse:
+ *    |         |             |
+ * seq_pool, seq_pool, ... seq_pool
+ *    \         |      ...   /
+ *            concat
+ *              |
+ * After fuse:
+ *    \      |       /
+ *   FusionSeqPoolConcat
+ *           |
+ */
 class SeqPoolConcatFusePass : public FusePassBase {
  public:
   virtual ~SeqPoolConcatFusePass() {}

paddle/fluid/operators/fused/fusion_seqpool_concat_op.cc

@@ -23,7 +23,7 @@ namespace operators {
 void FusionSeqPoolConcatOp::InferShape(
     framework::InferShapeContext* ctx) const {
   PADDLE_ENFORCE_GE(ctx->Inputs("X").size(), 1UL,
-                    "Inputs(X) of FusionSeqPoolConcatOp should be empty.");
+                    "Inputs(X) of FusionSeqPoolConcatOp should not be empty.");
   PADDLE_ENFORCE(ctx->HasOutput("Out"),
                  "Output(Out) of FusionSeqPoolConcatOp should not be null.");
   int axis = ctx->Attrs().Get<int>("axis");
@@ -54,12 +54,13 @@ void FusionSeqPoolConcatOpMaker::Make() {
   AddInput("X", "(LoDTensor) Input tensors of this operator.").AsDuplicable();
   AddOutput("Out", "(LoDTensor) Output tensor of concat operator.");
   AddAttr<std::string>("pooltype",
-                       "(string, default 'AVERAGE') some of the pooling "
+                       "(string, default 'SUM') some of the pooling "
                        "pooltype of SequencePoolOp.")
       .SetDefault("SUM")
       .InEnum({"AVERAGE", "SUM", "SQRT"});
   AddAttr<int>("axis",
-               "The axis along which the input tensors will be concatenated.")
+               "The axis along which the input tensors will be concatenated. "
+               "Only supports concat axis=1 yet.")
       .SetDefault(1);
   AddComment(R"DOC(
 Fusion Sequence Pool of pooltype(sum, average and sqrt) and Concat Operator.
@@ -100,6 +101,7 @@ class FusionSeqPoolConcatKernel : public framework::OpKernel<T> {
         jit::Get<jit::kSeqPool, jit::SeqPoolTuples<T>, platform::CPUPlace>(
             attr);
     size_t n = ins.size();
+    size_t dst_step_size = n * w;
     for (size_t i = 0; i < n; ++i) {
       auto x_dims = ins[i]->dims();
       auto x_lod = ins[i]->lod()[0];
@@ -112,7 +114,7 @@ class FusionSeqPoolConcatKernel : public framework::OpKernel<T> {
       for (size_t j = 0; j < bs; ++j) {
         attr.h = static_cast<int>(x_lod[j + 1] - x_lod[j]);
         seqpool(src, dst, &attr);
-        dst += n * w;
+        dst += dst_step_size;
         src += attr.h * attr.w;
       }
     }