- First draft of reusing of softmax mkldnn primitives

- Added hash function inside of MKLDNN softmax op to be used as handle for primitives stroing in a
context

- Style fixes to softmax mkldnn op

- Fixes after review

- Coding style

- Fix to style

- style fixes

- style fix

- style fixes

- Fix to cody style check

- Rephrasing a comment

paddle/fluid/operators/softmax_mkldnn_op.cc

@@ -53,25 +53,60 @@ class SoftmaxMKLDNNKernel : public paddle::framework::OpKernel<T> {
                    "Softmax input and output dimensions should match");
     // Same memory descriptor to be used for input and output
     memory::dims softmax_tz = {src_tz[0], src_tz[1]};
-    // Currently only supports NC data format
-    // TODO(jczaja-intel): support more formats
+    // Generate keys for storing/retriving primitives for this operator
+    // TODO(jczaja): Each MKLDNN operator may have diffrent hashing function
+    auto gethash = [](memory::dims& operand_dims) {
+      return std::string(std::to_string(operand_dims[0]) + "-" +
+                         std::to_string(operand_dims[1]));
+    };
+    const std::string key = gethash(softmax_tz);
+    const std::string key_softmax_p = key + "@softmax_p";
+    const std::string key_softmax_src_mem_p = key + "@softmax_src_mem_p";
+    const std::string key_softmax_dst_mem_p = key + "@softmax_dst_mem_p";
+
+    std::shared_ptr<void> softmax_p = dev_ctx.GetBlob(key_softmax_p);
+    if (softmax_p == nullptr) {
+      // Currently only NC data format is supported
       auto softmax_md =
           MKLDNNMemDesc({softmax_tz}, memory::f32, memory::format::nc);
       // Normalization is made after innermost dimension eg. C out of NC
       auto softmax_desc = softmax_forward::desc(prop_kind::forward_scoring,
                                                 softmax_md, 1 /*dim: C*/);
       // create memory primitives
-    auto softmax_src_memory =
-        memory({softmax_md, mkldnn_engine},
+      auto softmax_src_memory_p = std::make_shared<memory>(
+          memory::primitive_desc{softmax_md, mkldnn_engine},
           static_cast<void*>(const_cast<T*>(input_data)));
-    auto softmax_dst_memory =
-        memory({softmax_md, mkldnn_engine},
-               static_cast<void*>(const_cast<T*>(output_data)));
-    auto softmax_prim_desc =
-        softmax_forward::primitive_desc(softmax_desc, mkldnn_engine);
-    auto softmax = softmax_forward(softmax_prim_desc, softmax_src_memory,
-                                   softmax_dst_memory);
-    std::vector<primitive> pipeline{softmax};
+      dev_ctx.SetBlob(key_softmax_src_mem_p, softmax_src_memory_p);
+      auto softmax_dst_memory_p = std::make_shared<memory>(
+          memory::primitive_desc{softmax_md, mkldnn_engine},
+          static_cast<void*>(output_data));
+      dev_ctx.SetBlob(key_softmax_dst_mem_p, softmax_dst_memory_p);
+
+      auto softmax_forward_pd =
+          std::make_shared<softmax_forward::primitive_desc>(softmax_desc,
+                                                            mkldnn_engine);
+      softmax_p = std::make_shared<softmax_forward>(
+          *(softmax_forward_pd.get()),
+          *(static_cast<memory*>(softmax_src_memory_p.get())),
+          *(static_cast<memory*>(softmax_dst_memory_p.get())));
+      dev_ctx.SetBlob(key_softmax_p, softmax_p);
+    } else {
+      // Primitives already exist
+      auto src_memory_p = std::static_pointer_cast<memory>(
+          dev_ctx.GetBlob(key_softmax_src_mem_p));
+      PADDLE_ENFORCE(src_memory_p != nullptr,
+                     "Fail to find softmax src mem_p in device context");
+      auto dst_memory_p = std::static_pointer_cast<memory>(
+          dev_ctx.GetBlob(key_softmax_dst_mem_p));
+      PADDLE_ENFORCE(dst_memory_p != nullptr,
+                     "Fail to find softmax dst mem_p in device context");
+      src_memory_p->set_data_handle(
+          reinterpret_cast<void*>(const_cast<T*>(input_data)));
+      dst_memory_p->set_data_handle(output_data);
+    }
+
+    std::vector<primitive> pipeline{
+        *(static_cast<softmax_forward::primitive*>(softmax_p.get()))};
     stream(stream::kind::eager).submit(pipeline).wait();
 
     const bool is_test = ctx.Attr<bool>("is_test");