NAME

MPSCNNCrossChannelNormalizationGradient

SYNOPSIS

#import <MPSCNNNormalization.h>

Inherits MPSCNNGradientKernel.

Instance Methods

(nonnull instancetype) - initWithDevice:kernelSize:
(nullable instancetype) - initWithCoder:device:

Properties

float alpha
float beta
float delta
NSUInteger kernelSize

Detailed Description

This depends on Metal.framework Specifies the normalization gradient filter across feature channels. This normalization filter applies the filter to a local region across nearby feature channels, but with no spatial extent (i.e., they have shape kernelSize x 1 x 1). The normalized output is given by: Y(i,j,k) = X(i,j,k) / L(i,j,k)^beta, where the normalizing factor is: L(i,j,k) = delta + alpha/N * (sum_{q in Q(k)} X(i,j,q)^2, where N is the kernel size. The window Q(k) itself is defined as: Q(k) = [max(0, k-floor(N/2)), min(D-1, k+floor((N-1)/2)], where

k is the feature channel index (running from 0 to D-1) and D is the number of feature channels, and alpha, beta and delta are paremeters. It is the end-users responsibility to ensure that the combination of the parameters delta and alpha does not result in a situation where the denominator becomes zero - in such situations the resulting pixel-value is undefined.

OutputGradient: dZ/dX(i,j,k) = dZ/dY(i,j,k) * (L(i,j,k)^-beta) - 2 * alpha * beta * X(i,j,k) * ( sum_{r in R(k)} dZ/dY(i,j,r) * X(i,j,r) * (L(i,j,r) ^ (-beta-1)) ) N is the kernel size. The window L(i) and K(j) itself is defined as: R(k) = [max(0, k-floor((N-1)/2)), min(D-1, k+floor(N/2)]

For correct gradient computation all parameters must be the same as the original normalization filter.

Method Documentation

- (nullable instancetype) initWithCoder: (NSCoder *__nonnull) aDecoder(nonnull id< MTLDevice >) device

NSSecureCoding compatability While the standard NSSecureCoding/NSCoding method -initWithCoder: should work, since the file can't know which device your data is allocated on, we have to guess and may guess incorrectly. To avoid that problem, use initWithCoder:device instead.

Parameters:

aDecoder The NSCoder subclass with your serialized MPSKernel
device The MTLDevice on which to make the MPSKernel

Returns:

A new MPSKernel object, or nil if failure.

Reimplemented from MPSCNNGradientKernel.

- (nonnull instancetype) initWithDevice: (nonnull id< MTLDevice >) device(NSUInteger) kernelSize

Initialize a cross channel normalization gradient filter

Parameters:

device The device the filter will run on
kernelSize The kernel filter size in each dimension.

Returns:

A valid MPSCNNCrossChannelNormalization object or nil, if failure.

Property Documentation

- alpha [read], [write], [nonatomic], [assign]

The value of alpha. Default is 1.0. Must be non-negative.

- beta [read], [write], [nonatomic], [assign]

The value of beta. Default is 5.0

- delta [read], [write], [nonatomic], [assign]

The value of delta. Default is 1.0

- kernelSize [read], [nonatomic], [assign]

The size of the square filter window. Default is 5

Author

Generated automatically by Doxygen for MetalPerformanceShaders.framework from the source code.