MPSMatrixNeuron(3)

NAME
MPSMatrixNeuron

SYNOPSIS

#import <MPSMatrixNeuron.h>

Inherits MPSMatrixUnaryKernel.

  Instance Methods
(void) - setNeuronType:parameterA:parameterB:parameterC:
(MPSCNNNeuronType) - neuronType
(float) - neuronParameterA
(float) - neuronParameterB
(float) - neuronParameterC
(void) - setNeuronToPReLUWithParametersA:
(nonnull instancetype) - initWithDevice:
(void) - encodeToCommandBuffer:inputMatrix:biasVector:resultMatrix:
(nullable instancetype) - initWithCoder:device:
(nonnull instancetype) - copyWithZone:device:

  Properties
NSUInteger sourceNumberOfFeatureVectors
NSUInteger sourceInputFeatureChannels
double alpha

  Additional Inherited Members

Detailed Description

MPSMatrixNeuron.h MetalPerformanceShaders.framework

Copyright:
    Copyright (c) 2018 Apple Inc. All rights reserved. MPSMatrices fused with neurons

This depends on Metal.framework.

A neuron activation kernel that operates on matrices.

A MPSMatrixNeuron object computes:

            y = neuron(alpha * x + bias)
        y is the output matrix, x is the input matrix corresponding
        to a collection of input vectors and bias is a vector which is broadcast
        and accumulated to each row of the intermediate result.
        alpha is a scale factor applied to the input.
        neuron() defines the pointwise function that is applied to the intermediate result.
        Note: This function computes the same result as MPSMatrixFullyConnected that has
                unit weight matrix.

Method Documentation

  - (nonnull instancetype) copyWithZone: (nullable NSZone *) zone(nullable id< MTLDevice >) device
Make a copy of this kernel for a new device -

See also:
    MPSKernel

Parameters:
    zone The NSZone in which to allocate the object
    device The device for the new MPSKernel. If nil, then use self.device.

Returns:
    A pointer to a copy of this MPSKernel. This will fail, returning nil if the device is not supported. Devices must be MTLFeatureSet_iOS_GPUFamily2_v1 or later.

Reimplemented from MPSKernel.

  - (void) encodeToCommandBuffer: (nonnull id< MTLCommandBuffer >) commandBuffer(MPSMatrix *__nonnull) inputMatrix(MPSVector *__nullable) biasVector(MPSMatrix *__nonnull) resultMatrix
Encode a MPSMatrixNeuron object to a command buffer.

Parameters:
    commandBuffer A valid MTLCommandBuffer to receive the encoded kernel.
    inputMatrix A valid MPSMatrix object which specifies the input array.
    biasVector A valid MPSVector object which specifies the bias values, or a null object to indicate that no bias is to be applied.
    resultMatrix A valid MPSMatrix object which specifies the output array.

Encodes the operation to the specified command buffer. resultMatrix must be large enough to hold a MIN(sourceNumberOfFeatureVectors, inputMatrix.rows - sourceMatrixOrigin.x) x MIN(inputMatrix.columns - sourceMatrixOrigin.y, sourceInputFeatureChannels) array.

The bias vector must contain at least MIN(inputMatrix.columns - sourceMatrixOrigin.y, sourceInputFeatureChannels) elements.

  - (nullable instancetype) initWithCoder: (NSCoder *__nonnull) aDecoder(nonnull id< MTLDevice >) device
NSSecureCoding compatability See MPSKernel::initWithCoder.

Parameters:
    aDecoder The NSCoder subclass with your serialized MPSMatrixNeuron
    device The MTLDevice on which to make the MPSMatrixNeuron object.

Returns:
    A new MPSMatrixNeuron object, or nil if failure.

Reimplemented from MPSKernel.

  - (nonnull instancetype) initWithDevice: (nonnull id< MTLDevice >) device
Standard init with default properties per filter type

Parameters:
    device The device that the filter will be used on. May not be NULL.

Returns:
    a pointer to the newly initialized object. This will fail, returning nil if the device is not supported. Devices must be MTLFeatureSet_iOS_GPUFamily2_v1 or later.

Reimplemented from MPSKernel.

  - (float) neuronParameterA
Getter funtion for neuronType set using setNeuronType:parameterA:parameterB:parameterC method

  - (float) neuronParameterB
Getter funtion for neuronType set using setNeuronType:parameterA:parameterB:parameterC method

  - (float) neuronParameterC
Getter funtion for neuronType set using setNeuronType:parameterA:parameterB:parameterC method

  - (MPSCNNNeuronType) neuronType
Getter funtion for neuronType set using setNeuronType:parameterA:parameterB:parameterC method

  - (void) setNeuronToPReLUWithParametersA: (NSData *__nonnull) A
Add per output value neuron parameters A for PReLu neuron activation functions.

This method sets the neuron to PReLU, zeros parameters A and B and sets the per output value neuron parameters A to an array containing a unique value of A for each output value.

If the neuron function is f(v,a,b), it will apply

   resultMatrix(i, j) = f( input(i, j), A[j], B[j] )
where j in [0, sourceInputFeatureChannels]

See https://arxiv.org/pdf/1502.01852.pdf for details.

All other neuron types, where parameter A and parameter B are shared across output values must be set using -setNeuronType:parameterA:parameterB:

Parameters:
    A An array containing float values for neuron parameter A. Number of entries must be equal to MIN(inputMatrix.columns - sourceMatrixOrigin.y, sourceInputFeatureChannels)

  - (void) setNeuronType: (MPSCNNNeuronType) neuronType(float) parameterA(float) parameterB(float) parameterC
Specifies a neuron activation function to be used.

This method can be used to add a neuron activation funtion of given type with associated scalar parameters A, B, and C that are shared across all output values. Note that this method can only be used to specify neurons which are specified by three (or fewer) parameters shared across all output values (or channels, in CNN nomenclature). It is an error to call this method for neuron activation functions like MPSCNNNeuronTypePReLU, which require per-channel parameter values. For those kind of neuron activation functions, use appropriate setter functions. An MPSMatrixNeuron kernel is initialized with a default neuron function of MPSCNNNeuronTypeNone.

Parameters:
    neuronType Type of neuron activation function. For full list see MPSCNNNeuronType.h
    parameterA parameterA of neuron activation that is shared across all output values.
    parameterB parameterB of neuron activation that is shared across all output values.
    parameterC parameterC of neuron activation that is shared across all output values.

Property Documentation

  - alpha [read], [write], [nonatomic], [assign]
The scale factor to apply to the input. Specified in double precision. Will be converted to the appropriate precision in the implementation subject to rounding and/or clamping as necessary. Defaults to 1.0 at initialization time.

  - sourceInputFeatureChannels [read], [write], [nonatomic], [assign]
The input size to to use in the operation. This is equivalent to the number of columns in the primary (input array) source matrix to consider and the number of channels to produce for the output matrix. This property is modifiable and defaults to NSUIntegerMax. At encode time the larger of this property or the available input size is used. The value of NSUIntegerMax thus indicates that all available columns in the input array (beginning at sourceMatrixOrigin.y) should be considered. Defines also the number of output feature channels. Note: The value used in the operation will be MIN(inputMatrix.columns - sourceMatrixOrigin.y, sourceInputFeatureChannels)

  - sourceNumberOfFeatureVectors [read], [write], [nonatomic], [assign]
The number of input vectors which make up the input array. This is equivalent to the number of rows to consider from the primary source matrix. This property is modifiable and defaults to NSUIntegerMax. At encode time the larger of this property or the available number of inputs is used. The value of NSUIntegerMax thus indicates that all available input rows (beginning at sourceMatrixOrigin.x) should be considered.

Author

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