Class: Chainer::Functions::Array::Squeeze

Inherits:
Chainer::FunctionNode show all
Defined in:
lib/chainer/functions/array/squeeze.rb

Instance Attribute Summary

Attributes inherited from Chainer::FunctionNode

#inputs, #outputs, #rank

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Chainer::FunctionNode

#apply, #backward_accumulate, #forward_cpu, #get_retained_inputs, #get_retained_outputs, #label, #output_data, #retain_inputs, #retain_outputs, #unchain

Constructor Details

#initialize(axis: nil) ⇒ Squeeze

Returns a new instance of Squeeze.



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# File 'lib/chainer/functions/array/squeeze.rb', line 15

def initialize(axis: nil)
  if axis.nil?
    @axis = nil
  elsif axis.kind_of?(Integer)
    @axis = [axis]
  elsif axis.kind_of?(::Array) && Array(axis).all? { |i| i.kind_of?(Integer) }
    @axis = axis
  else
    raise TypeError, 'axis must be None, int or tuple of ints'
  end
end

Class Method Details

.squeeze(x, axis: nil) ⇒ Chainer::Variable

Remove demensions of size one from the shape of a Numo::NArray.

Parameters:

  • x (Chainer::Variable or Numo::NArray) —

    Input data.

  • axis (nil or integer or array of integer) (defaults to: nil) —

    A subset of the single-dimensional entries in the shape to remove. If nil is supplied, all of them are removed. The dimension index starts at zero. If an axis with dimension greater than one is selected, an error is raised.

Returns:



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# File 'lib/chainer/functions/array/squeeze.rb', line 11

def self.squeeze(x, axis: nil)
  self.new(axis: axis).apply([x]).first
end

Instance Method Details

#backward(indexes, grad_outputs) ⇒ Object 



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# File 'lib/chainer/functions/array/squeeze.rb', line 47

def backward(indexes, grad_outputs)
  if @axis.nil?
    axis = argone(@inputs[0].shape)
  else
    axis = @axis
    ndim = @inputs[0].shape.size
    axis = axis.map { |x| x < 0 ? x + ndim : x }
    axis.sort!
  end
  gx = grad_outputs.first

  shape = gx.shape
  axis.each do |x|
    shape.insert(x, 1)
  end
  [gx.reshape(*shape)]
end

#forward(inputs) ⇒ Object 



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# File 'lib/chainer/functions/array/squeeze.rb', line 27

def forward(inputs)
  x = inputs.first
  shape = x.shape

  # TODO: numpy.squeeze
  if @axis.nil?
    new_shape = shape.reject { |axis| axis == 1 }
  else
    new_shape = shape
    @axis.map do |a|
      raise StandardError, "cannot select an axis to squeeze out which has size not equal to one" unless shape[a] == 1
      new_shape[a] = nil
    end
    new_shape.compact!
  end
  ret = new_shape.size.zero? ? x.class.new.fill(x[0]) : x.reshape(*new_shape)

  [ret]
end