ArmNN
 24.08
Softmax.cpp
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1 //
2 // Copyright © 2017, 2024 Arm Ltd. All rights reserved.
3 // SPDX-License-Identifier: MIT
4 //
5 
6 #include "Softmax.hpp"
7 
9 
10 #include <cmath>
11 #include <vector>
12 
13 namespace armnn
14 {
15 
16 /// Computes the softmax function on some inputs, into outputs, with a shape given by tensorInfo.
17 void Softmax(Decoder<float>& in, Encoder<float>& out, const TensorInfo& inputTensorInfo, float beta, int axis)
18 {
19  ARMNN_THROW_INVALIDARG_MSG_IF_FALSE(axis < static_cast<int>(inputTensorInfo.GetNumDimensions()),
20  "Required axis index greater than number of dimensions.");
21  ARMNN_THROW_INVALIDARG_MSG_IF_FALSE(axis >= -static_cast<int>(inputTensorInfo.GetNumDimensions()),
22  "Required axis index lower than negative of the number of dimensions");
23 
24  unsigned int uAxis = axis < 0 ?
25  inputTensorInfo.GetNumDimensions() - static_cast<unsigned int>(abs(axis))
26  : static_cast<unsigned int>(axis);
27 
28  const TensorShape& inputShape = inputTensorInfo.GetShape();
29  const unsigned int outerSize = armnnUtils::GetNumElementsBetween(inputShape, 0, uAxis);
30  const unsigned int axisSize = inputShape[uAxis];
31  const unsigned int innerSize = armnnUtils::GetNumElementsBetween(inputShape,
32  uAxis + 1,
33  inputShape.GetNumDimensions());
34 
35  for (unsigned int outer = 0; outer < outerSize; ++outer)
36  {
37  unsigned int inputBeginIdx = outer * axisSize * innerSize;
38  unsigned int inputEndIdx = inputBeginIdx + axisSize * innerSize;
39  unsigned int outputBeginIdx = outer * axisSize * innerSize;
40 
41  for (unsigned int inner = 0; inner < innerSize; ++inner, ++inputBeginIdx, ++inputEndIdx, ++outputBeginIdx)
42  {
43  // Find max
44  float maxValue = std::numeric_limits<float>::lowest();
45  for (unsigned int iter = inputBeginIdx; iter < inputEndIdx; iter += innerSize)
46  {
47  in[iter];
48  maxValue = std::max(maxValue, in.Get());
49  }
50 
51  // Compute sum
52  float sum = 0.0f;
53  for (unsigned int iter = inputBeginIdx; iter < inputEndIdx; iter += innerSize)
54  {
55  in[iter];
56  sum += std::exp((in.Get() - maxValue) * beta);
57  }
58 
59  // Compute result
60  unsigned int outputIter = outputBeginIdx;
61  out[outputIter];
62  for (unsigned int iter = inputBeginIdx; iter < inputEndIdx; iter += innerSize, outputIter += innerSize)
63  {
64  out[outputIter];
65  in[iter];
66  out.Set(std::exp((in.Get() - maxValue) * beta) / sum);
67  }
68  }
69  }
70 }
71 
72 } //namespace armnn
armnn::Decoder< float >
armnn::Encoder::Set
virtual void Set(IType right)=0
armnn::TensorInfo
Definition: Tensor.hpp:152
armnn::TensorInfo::GetNumDimensions
unsigned int GetNumDimensions() const
Definition: Tensor.hpp:197
TensorUtils.hpp
armnn::TensorShape
Definition: Tensor.hpp:20
armnn::Encoder< float >
armnn::TensorShape::GetNumDimensions
unsigned int GetNumDimensions() const
Function that returns the tensor rank.
Definition: Tensor.cpp:174
armnn::Softmax
void Softmax(Decoder< float > &in, Encoder< float > &out, const TensorInfo &inputTensorInfo, float beta, int axis)
Computes the softmax function on some inputs, into outputs, with a shape given by tensorInfo.
Definition: Softmax.cpp:17
armnn::Decoder::Get
virtual IType Get() const =0
Softmax.hpp
armnnUtils::GetNumElementsBetween
unsigned int GetNumElementsBetween(const armnn::TensorShape &shape, unsigned int firstAxisInclusive, unsigned int lastAxisExclusive)
Definition: TensorUtils.cpp:209
armnn::abs
Definition: Abs.hpp:13
armnn::TensorInfo::GetShape
const TensorShape & GetShape() const
Definition: Tensor.hpp:193
armnn
Copyright (c) 2021 ARM Limited and Contributors.
Definition: 01_00_quick_start.dox:6
ARMNN_THROW_INVALIDARG_MSG_IF_FALSE
#define ARMNN_THROW_INVALIDARG_MSG_IF_FALSE(_cond, _str)
Definition: Exceptions.hpp:210