Support 3D input for MKL-DNN softmax operator

src/operator/nn/mkldnn/mkldnn_base-inl.h

@@ -180,7 +180,7 @@ bool SupportMKLDNNAct(const ActivationParam& param);
 bool SupportMKLDNNAct(const ActivationParam& param, const NDArray &input);
 bool SupportMKLDNNConv(const ConvolutionParam& params, const NDArray &input);
 bool SupportMKLDNNDeconv(const DeconvolutionParam& params, const NDArray &input);
-bool SupportMKLDNNSoftmax(const SoftmaxParam& param);
+bool SupportMKLDNNSoftmax(const SoftmaxParam& param, const NDArray &input, const NDArray &output);
 bool SupportMKLDNNSoftmaxOutput(const SoftmaxOutputParam &param);
 bool SupportMKLDNNTranspose(const TransposeParam& param, const NDArray &data);
 }  // namespace op

src/operator/nn/mkldnn/mkldnn_softmax.cc

@@ -26,43 +26,66 @@
 #include "../softmax-inl.h"
 #include "./mkldnn_ops-inl.h"
 #include "./mkldnn_base-inl.h"
-#include "../../tensor/broadcast_reduce_op.h"
 
 #if MXNET_USE_MKLDNN == 1
 namespace mxnet {
 namespace op {
 
-bool SupportMKLDNNSoftmax(const SoftmaxParam &param) {
+bool SupportMKLDNNSoftmax(const SoftmaxParam &param,
+                          const NDArray &data,
+                          const NDArray &output) {
+  const int ndim = data.shape().ndim();
+  const int in_dtype = data.dtype();
+  const int out_dtype = output.dtype();
+
+  const int axis = CheckAxis(param.axis, ndim);
   // MKLDNN does not support temperature argument in their softmax function
   // now. Need update this once they start to support it.
-  if (param.temperature.has_value()) {
+  // Currently, MKLDNN shows bad performance when softmax is not performed on the last dimension
+  if (param.temperature.has_value() ||
+      in_dtype != mshadow::kFloat32 ||
+      in_dtype != out_dtype ||
+      axis != (ndim - 1)) {
     return false;
   }
-  return true;
+  // only supports ndim = 1, 2, 3, 4 for now
+  return (ndim >= 1 && ndim <= 4);
+}
+
+static mkldnn::softmax_forward::primitive_desc GetSoftmaxFwdPd(const int axis,
+                                                               const bool is_train,
+                                                               const mkldnn::memory &input) {
+  auto data_md = input.get_primitive_desc().desc();
+  auto prop = is_train ? mkldnn::prop_kind::forward_training : mkldnn::prop_kind::forward_scoring;
+  auto desc = mkldnn::softmax_forward::desc(prop, data_md, axis);
+  auto pd = mkldnn::softmax_forward::primitive_desc(desc, CpuEngine::Get()->get_engine());
+  return pd;
 }
 
-void MKLDNNSoftmaxForward(const nnvm::NodeAttrs& attrs, const OpContext &ctx,
-                          const NDArray &in_data, const OpReqType &req,
+void MKLDNNSoftmaxForward(const nnvm::NodeAttrs &attrs,
+                          const OpContext &ctx,
+                          const NDArray &in_data,
+                          const OpReqType &req,
                           const NDArray &out_data) {
+  if (req == kNullOp) return;
+  // same as the FCompute path, softmax only supports kWriteTo and kWriteInplace for now.
+  CHECK_NE(req, kAddTo);
   const SoftmaxParam& param = nnvm::get<SoftmaxParam>(attrs.parsed);
-  auto input_mem = in_data.GetMKLDNNData();
-  mkldnn::memory::primitive_desc data_mpd = input_mem->get_primitive_desc();
-  mkldnn::memory::desc data_md = data_mpd.desc();
-  int axis = CheckAxis(param.axis, in_data.shape().ndim());
+  const int axis = CheckAxis(param.axis, in_data.shape().ndim());
 
-  auto cpu_engine = data_mpd.get_engine();
-  auto prop = ctx.is_train
-    ? mkldnn::prop_kind::forward_training : mkldnn::prop_kind::forward_scoring;
-  mkldnn::softmax_forward::desc desc = mkldnn::softmax_forward::desc(prop,
-      data_md, axis);
-  mkldnn::softmax_forward::primitive_desc pdesc(desc, cpu_engine);
+  NDArray data = in_data;
+  if (in_data.IsView() && in_data.IsMKLDNNData()) {
+    data = in_data.Reorder2Default();
+  }
 
-  auto output_memory = out_data.GetMKLDNNData();
+  auto data_mem = data.GetMKLDNNData();
+  auto pd = GetSoftmaxFwdPd(axis, ctx.is_train, *data_mem);
+  auto out_mem = CreateMKLDNNMem(out_data, pd.dst_primitive_desc(), req);
   MKLDNNStream *stream = MKLDNNStream::Get();
-  stream->RegisterPrim(mkldnn::softmax_forward(pdesc, *input_mem, *output_memory));
+  stream->RegisterPrim(mkldnn::softmax_forward(pd, *data_mem, *out_mem.second));
+  CommitOutput(out_data, out_mem);
   stream->Submit();
 }
-
 }   // namespace op
 }   // namespace mxnet
 #endif

src/operator/nn/softmax.cc

@@ -43,7 +43,7 @@ static void SoftmaxComputeExCPU(const nnvm::NodeAttrs& attrs,
                                 const std::vector<NDArray>& outputs) {
   // It seems MKLDNN softmax doesn't support training.
   const SoftmaxParam& param = nnvm::get<SoftmaxParam>(attrs.parsed);
-  if (SupportMKLDNN(inputs[0]) && !ctx.is_train && SupportMKLDNNSoftmax(param)) {
+  if (SupportMKLDNNSoftmax(param, inputs[0], outputs[0])) {
     MKLDNN_OPCHECK_INIT(false, outputs.size(), inputs, outputs);
     MKLDNNSoftmaxForward(attrs, ctx, inputs[0], req[0], outputs[0]);
     auto fn = SoftmaxCompute<cpu, mxnet_op::softmax_fwd>;