From e39dfae2dc5d06971b7993e3dddc8b9e4817bf69 Mon Sep 17 00:00:00 2001
From: "Efimov Alexander/AI Tools Lab/./Samsung Electronics"
 <a.efimov@samsung.com>
Date: Wed, 22 Aug 2018 16:09:17 +0300
Subject: [PATCH] Add support of negative axis in softmax (#1117)

Use negative parameter in softmax operation to count axises from last one
---
 .../include/nnc/core/IR/model/operations/softmax_op.h   | 13 ++++++++++++-
 .../nnc/libs/frontend/caffe/src/caffe_op_creator.cpp    |  3 ++-
 .../nnc/libs/frontend/tflite/src/tflite_op_creator.cpp  |  4 ++--
 contrib/nnc/unittests/core/operation.cpp                | 17 +++++++++++++++++
 4 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/contrib/nnc/libs/core/include/nnc/core/IR/model/operations/softmax_op.h b/contrib/nnc/libs/core/include/nnc/core/IR/model/operations/softmax_op.h
index e9d6f5b..091dcdb 100644
--- a/contrib/nnc/libs/core/include/nnc/core/IR/model/operations/softmax_op.h
+++ b/contrib/nnc/libs/core/include/nnc/core/IR/model/operations/softmax_op.h
@@ -21,7 +21,18 @@ class SoftmaxOp : public OpDescription
 public:
   explicit SoftmaxOp(int axis) : OpDescription(1, 1), _axis(axis) {}
 
-  int getAxis() const { return _axis; }
+  int getAxis() const
+  {
+    if (_axis < 0)
+    {
+      // Negative axis is used to index starting from the last element of the shape
+      // -1 means last element, -2 means second from end, like in python
+      int res = _axis + getInputShape(0).rank();
+      assert(res >= 0);
+      return res;
+    }
+    return _axis;
+  }
 
 private:
   int _axis;
diff --git a/contrib/nnc/libs/frontend/caffe/src/caffe_op_creator.cpp b/contrib/nnc/libs/frontend/caffe/src/caffe_op_creator.cpp
index edf18df..2d41440 100644
--- a/contrib/nnc/libs/frontend/caffe/src/caffe_op_creator.cpp
+++ b/contrib/nnc/libs/frontend/caffe/src/caffe_op_creator.cpp
@@ -234,7 +234,8 @@ __attribute__ ((unused)) static ops::PoolOp::PoolingType getPoolingType(const Po
 template <typename OptsType>
 __attribute__ ((unused)) static int getAxisValue(const OptsType& opts)
 {
-  int axis = 2;
+  // -1 represents last one dimension
+  int axis = -1;
   if (opts.has_axis())
   {
     axis = opts.axis();
diff --git a/contrib/nnc/libs/frontend/tflite/src/tflite_op_creator.cpp b/contrib/nnc/libs/frontend/tflite/src/tflite_op_creator.cpp
index 2f7e84e..d5cab37 100644
--- a/contrib/nnc/libs/frontend/tflite/src/tflite_op_creator.cpp
+++ b/contrib/nnc/libs/frontend/tflite/src/tflite_op_creator.cpp
@@ -76,8 +76,8 @@ std::vector<INode::Ref> OpCreator::createAvgPool(InputOps inputs, InputParams pa
 std::vector<INode::Ref> OpCreator::createSoftmax(InputOps inputs, InputParams params,
                                                  const SoftmaxOptions *opts)
 {
-  // TODO: here assuming that softmax is applied to a 1-d tensor
-  return createOp<ops::SoftmaxOp>(inputs, ActivationFunctionType_NONE, 1);
+  // -1 represents last one dimension
+  return createOp<ops::SoftmaxOp>(inputs, ActivationFunctionType_NONE, -1);
 }
 
 std::vector<INode::Ref> OpCreator::createReshape(InputOps inputs, InputParams params,
diff --git a/contrib/nnc/unittests/core/operation.cpp b/contrib/nnc/unittests/core/operation.cpp
index 35f34e5..3944fb4 100644
--- a/contrib/nnc/unittests/core/operation.cpp
+++ b/contrib/nnc/unittests/core/operation.cpp
@@ -1,4 +1,5 @@
 #include "nnc/core/IR/model/operations/operation.h"
+#include "nnc/core/IR/model/operations/softmax_op.h"
 
 #include <gtest/gtest.h>
 
@@ -16,3 +17,19 @@ TEST(OpDescription, InputOutputShapeTest) {
   ASSERT_EQ(inShape, op.getInputShape(0));
   ASSERT_EQ(outShape, op.getOutputShape(0));
 }
+
+TEST(OpDescription, SoftmaxAxisTest) {
+  Shape inShape{1,2,3};
+
+  ops::SoftmaxOp op_1(1);
+  op_1.setInputShape(0, inShape);
+  ASSERT_EQ(op_1.getAxis(), 1);
+
+  ops::SoftmaxOp op_n1(-1);
+  op_n1.setInputShape(0, inShape);
+  ASSERT_EQ(op_n1.getAxis(), 2);
+
+  ops::SoftmaxOp op_n3(-3);
+  op_n3.setInputShape(0, inShape);
+  ASSERT_EQ(op_n3.getAxis(), 0);
+}
\ No newline at end of file
-- 
2.7.4