clean code

paddle/fluid/operators/math/sequence_pooling.cc

@@ -113,33 +113,34 @@ class LastFirstSeqPoolFunctor {
   auto* in_data = input.data<T>();
   auto* out_data = output->data<T>();
 
-  //Calculate length of each word
-  int64_t word_len = input.numel() / input.dims()[0];
+  //Calculate the size of each item in sequence
+  int64_t item_size = input.numel() / input.dims()[0];
   auto lod = input.lod()[0];
+  int seq_num = static_cast<int>(lod.size()) - 1;
   if (pooltype == "LAST"){
-      for (int i=0;  i < static_cast<int>(lod.size()) - 1; ++i ){
+      for (int i=0;  i < seq_num; ++i ){
             //Calculate the length of each sequence
             int64_t seq_len =  static_cast<int64_t>(lod[i + 1] - lod[i]);
             //Point to the begin of next sequence
-            in_data += seq_len* word_len;
-            //Copy the last words to output
-            std::memcpy(out_data,(in_data-word_len),word_len*sizeof(T));
-            out_data += word_len;
-            
+            in_data += seq_len* item_size;
+            //Copy the last item to output
+            std::memcpy(out_data,(in_data-item_size),item_size*sizeof(T));
+            out_data += item_size;
        }
   }
   else if(pooltype == "FIRST"){
-      for (int i=0;  i < static_cast<int>(lod.size()) - 1; ++i ){
+      for (int i=0;  i < seq_num; ++i ){
             //Calculate the length of each sequence 
             int64_t seq_len =  static_cast<int64_t>(lod[i + 1] - lod[i]);
-            //Copy the first words of sequence to output
-            std::memcpy(out_data,in_data,word_len*sizeof(T));
+            //Copy the first item of sequence to output
+            std::memcpy(out_data,in_data,item_size*sizeof(T));
             //Point to the next sequence
-            in_data += seq_len * word_len;
-            out_data += word_len;
-
+            in_data += seq_len * item_size;
+            out_data += item_size;
        }
-
+     }
+   else {
+        PADDLE_THROW("it's not LAST or FIRST pool type");
       }
    }
 };