ActivationFunction.cpp

/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License. */

#include "ActivationFunction.h"

#include <algorithm>
#include <iostream>
#include <memory>
#include <string>
#include <thread>
#include <type_traits>
#include "paddle/parameter/Argument.h"
#include "paddle/utils/ClassRegistrar.h"

#include "paddle/utils/Logging.h"

namespace paddle {

static ClassRegistrar<ActivationFunction> gActivationRegistrar;
/**
 * @def ACTIVATION_CLASS_NAME
 * @brief Macro for getting derived activation class name
 * @note ACTIVATION_CLASS_NAME(softmax) softmax_;
 * means softmaxActivation softmax_;
 */
#define ACTIVATION_CLASS_NAME(ACTIVATION_NAME) ACTIVATION_NAME##Activation
/**
 * @def BEGIN_DEFINE_ACTIVATION
 * @brief Macro for defining a devried activation class
 */
#define BEGIN_DEFINE_ACTIVATION(ACTIVATION_NAME)                             \
  class ACTIVATION_CLASS_NAME(ACTIVATION_NAME) : public ActivationFunction { \
  private:                                                                   \
    static const std::string name;                                           \
                                                                             \
  public:                                                                    \
    const std::string& getName() const { return name; }
/**
 * @def END_DEFINE_ACTIVATION
 * @brief Macro for registering a derived activation class
 */
#define END_DEFINE_ACTIVATION(ACTIVATION_NAME)                     \
  }                                                                \
  ;                                                                \
  const std::string ACTIVATION_CLASS_NAME(ACTIVATION_NAME)::name = \
      #ACTIVATION_NAME;                                            \
  static InitFunction __reg_activation__##ACTIVATION_NAME([] {     \
    gActivationRegistrar                                           \
        .registerClass<ACTIVATION_CLASS_NAME(ACTIVATION_NAME)>(    \
            #ACTIVATION_NAME);                                     \
  });

/**
 * @brief The IdentityActivation class
 *
 * Do nothing when forward/backward.
 */
class IdentityActivation : public ActivationFunction {
public:
  static const std::string name;
  Status forward(Argument& act) {
    (void)act;
    return Status();
  }
  Status backward(Argument& act) {
    (void)act;
    return Status();
  }
  const std::string& getName() const { return name; }
};
const std::string IdentityActivation::name = "";
static InitFunction __reg_activation__identity([] {
  gActivationRegistrar.registerClass<IdentityActivation>("");
  gActivationRegistrar.registerClass<IdentityActivation>("linear");
});

/**
 * @brief Sigmoid Activation
 * \f[
 * f(z) = \frac{1}{1+exp(-z)}
 * \f]
 */
BEGIN_DEFINE_ACTIVATION(sigmoid)
Status forward(Argument& act) {
  act.value->sigmoid(*act.value);
  return Status();
}
Status backward(Argument& act) {
  act.grad->sigmoidDerivative(*act.value);
  return Status();
}
END_DEFINE_ACTIVATION(sigmoid)

/**
 * @brief Softmax Activation
 * \f[
 * P(y=j|x) = \frac{e^{x^Tw_j}}{\sum^K_{k=1}e^{x^Tw_k}}
 * \f]
 */
BEGIN_DEFINE_ACTIVATION(softmax)
private:
MatrixPtr sftMaxSum_;
MatrixPtr sftMaxDot_;
MatrixPtr one_;

public:
Status forward(Argument& act) {
  act.value->softmax(*act.value);
  return Status();
}

Status backward(Argument& act) {
  MatrixPtr outputV = act.value;
  MatrixPtr outputG = act.grad;

  if (outputG->useGpu()) {
    outputG->softmaxBackward(*outputV);
  } else {
    SetDevice device(act.deviceId);
    Matrix::resizeOrCreate(sftMaxDot_,
                           outputG->getHeight(),
                           outputG->getWidth(),
                           /* trans */ false,
                           useGpu(act.deviceId));
    Matrix::resizeOrCreate(sftMaxSum_,
                           outputG->getHeight(),
                           1,
                           /* trans */ false,
                           useGpu(act.deviceId));
    if (!one_ || one_->getWidth() != outputG->getWidth()) {
      Matrix::resizeOrCreate(one_,
                             1,
                             outputG->getWidth(),
                             /* trans */ false,
                             useGpu(act.deviceId));
      one_->one();
    }

    sftMaxDot_->dotMul(*outputG, *outputV);
    sftMaxSum_->colMerge(*sftMaxDot_);

    act.grad->softmaxDerivative(*act.value, *sftMaxSum_);
  }
  return Status();
}
END_DEFINE_ACTIVATION(softmax)

/**
 * @brief Sequence_softmax Activation
 * @note Softmax on all frames of one sequence.
 * Width of frame must be one.
 */
BEGIN_DEFINE_ACTIVATION(sequence_softmax)
private:
ACTIVATION_CLASS_NAME(softmax) softmax_;
Argument argument_;

public:
Status forward(Argument& act) {
  if (act.value->getWidth() != 1UL) {
    return Status(
        "Input width for each timestep of sequence softmax should be 1");
  }

  if (!argument_.value) {
    argument_.value = Matrix::create(nullptr,
                                     /* height= */ 1,
                                     1,
                                     /* trans= */ false,
                                     useGpu(act.deviceId));
    argument_.grad = Matrix::create(nullptr,
                                    /* height= */ 1,
                                    1,
                                    /* trans= */ false,
                                    useGpu(act.deviceId));
  }

  auto starts = act.sequenceStartPositions->getVector(useGpu(act.deviceId));
  act.value->sequenceSoftmax(*act.value, *starts);
  return Status();
}

Status backward(Argument& act) {
  if (act.value->getWidth() != 1UL) {
    return Status(
        "Input width for each timestep of sequence softmax should be 1");
  }

  size_t numSequences = act.getNumSequences();
  const int* starts = act.sequenceStartPositions->getData(false);

  for (size_t i = 0; i < numSequences; ++i) {
    // TODO(Dangqingqing) optimization for GPU
    size_t offset = starts[i];
    size_t size = starts[i + 1] - starts[i];
    argument_.value->setData(act.value->getData() + offset, 1UL, size);
    argument_.grad->setData(act.grad->getData() + offset, 1UL, size);

    softmax_.backward(argument_);
  }
  return Status();
}
END_DEFINE_ACTIVATION(sequence_softmax)

/**
 * @brief Relu Activation.
 * forward. y = max(0, z)
 *
 * derivative of relu is:
 *
 *    1 if z > 0
 *
 *    0 otherwise.
 */
BEGIN_DEFINE_ACTIVATION(relu)
Status forward(Argument& act) {
  act.value->relu(*act.value);
  return Status();
}

Status backward(Argument& act) {
  act.grad->reluDerivative(*act.value);
  return Status();
}
END_DEFINE_ACTIVATION(relu)

/**
 * @brief BRelu Activation.
 *
 * forward. y = min(24, max(0, z))
 *
 * derivative of brelu is:
 *
 *    1 if 0 < z < 24
 *
 *    0 otherwise.
 *
 * TODO(yuyang18): Remove magic number 24 or make it configuable.
 */
BEGIN_DEFINE_ACTIVATION(brelu)
Status forward(Argument& act) {
  act.value->brelu(*act.value);
  return Status();
}

Status backward(Argument& act) {
  act.grad->breluDerivative(*act.value);
  return Status();
}
END_DEFINE_ACTIVATION(brelu)

/**
 * @brief Tanh Activation.
 * \f[
 * f(z) = tanh(z)=\frac{e^z-e^{-z}}{e^z+e^{-z}}
 * \f]
 */
BEGIN_DEFINE_ACTIVATION(tanh)
Status forward(Argument& act) {
  act.value->tanh(*act.value);
  return Status();
}

Status backward(Argument& act) {
  act.grad->tanhDerivative(*act.value);
  return Status();
}
END_DEFINE_ACTIVATION(tanh)

/**
 * @brief Scaled Tanh Activation
 * \f[
 * f(z) = 1.7159 * tanh(2/3*z)
 * \f]
 */
BEGIN_DEFINE_ACTIVATION(stanh)
private:
real a, b;

public:
ACTIVATION_CLASS_NAME(stanh)() : a(1.7159), b(2. / 3.) {}
Status forward(Argument& act) {
  act.value->scaledTanh(*act.value, a, b);
  return Status();
}

Status backward(Argument& act) {
  act.grad->scaledTanhDerivative(*act.value, a, b);
  return Status();
}
END_DEFINE_ACTIVATION(stanh)

/**
 * @brief Soft Relu Activation.
 * \f[
 * f(z) = ln(1+e^z)
 * \f]
 */
BEGIN_DEFINE_ACTIVATION(softrelu)
Status forward(Argument& act) {
  act.value->softrelu(*act.value);
  return Status();
}

Status backward(Argument& act) {
  act.grad->softreluDerivative(*act.value);
  return Status();
}
END_DEFINE_ACTIVATION(softrelu)

/**
 * @brief Abs Activation.
 * Forward: f(z) = abs(z)
 *
 * Derivative:
 *
 *     1   if z>0
 *
 *    -1   if z<0
 *
 *     0   if z=0
 */
BEGIN_DEFINE_ACTIVATION(abs)
Status forward(Argument& act) {
  SetDevice device(act.deviceId);
  Matrix::resizeOrCreate(act.in,
                         act.value->getHeight(),
                         act.value->getWidth(),
                         /* trans */ false,
                         useGpu(act.deviceId));

  act.in->copyFrom(*act.value);
  act.value->abs2(*act.value);
  return Status();
}

Status backward(Argument& act) {
  act.grad->absDerivative(*act.in);
  return Status();
}
END_DEFINE_ACTIVATION(abs)

/**
 * @brief Square Activation.
 * \f[
 * f(z) = z^2.
 * \f]
 */
BEGIN_DEFINE_ACTIVATION(square)
Status forward(Argument& act) {
  SetDevice device(act.deviceId);
  Matrix::resizeOrCreate(act.in,
                         act.value->getHeight(),
                         act.value->getWidth(),
                         /* trans */ false,
                         useGpu(act.deviceId));

  act.in->copyFrom(*act.value);
  act.value->square2(*act.value);
  return Status();
}

Status backward(Argument& act) {
  act.grad->squareDerivative(*act.in);
  return Status();
}
END_DEFINE_ACTIVATION(square)

/**
 * @brief Exponential Activation.
 * \f[
 * f(z) = e^z
 * \f]
 */
BEGIN_DEFINE_ACTIVATION(exponential)
Status forward(Argument& act) {
  act.value->exp2(*act.value);
  return Status();
}

Status backward(Argument& act) {
  act.grad->expDerivative(*act.value);
  return Status();
}
END_DEFINE_ACTIVATION(exponential)

/**
 * @brief Logarithm Activation.
 * \f[
 * f(z) = log(z)
 * \f]
 */
BEGIN_DEFINE_ACTIVATION(log)
Status forward(Argument& act) {
  SetDevice device(act.deviceId);
  Matrix::resizeOrCreate(act.in,
                         act.value->getHeight(),
                         act.value->getWidth(),
                         /* trans */ false,
                         useGpu(act.deviceId));

  act.in->copyFrom(*act.value);
  act.value->log2(*act.value);
  return Status();
}

Status backward(Argument& act) {
  act.grad->dotDiv(*act.grad, *act.in);
  return Status();
}
END_DEFINE_ACTIVATION(log)

ActivationFunction* ActivationFunction::create(const std::string& type) {
  return gActivationRegistrar.createByType(type);
}

std::vector<std::string> ActivationFunction::getAllRegisteredTypes() {
  std::vector<std::string> types;
  gActivationRegistrar.forEachType(
      [&](const std::string& type) { types.push_back(type); });
  return types;
}

}  // namespace paddle