Module: NumRu::Misc::MD_Iterators

Included in:
NArray
Defined in:
lib/numru/misc/md_iterators.rb

Overview

A Mixin. To be included in a class with multi-dimension indexing support (such as NArray).

Instance Method Summary collapse

Instance Method Details

#each_subary_at_dims(*dims) ⇒ Object

Iterator for each sub-array (not each element) specified by dimensions.

ARGUMENT

*dims (integers) : specifies subsets at dimensions specified here with the beginning-to-end selection. For example, [0, 1] to specify the first 2 dimensions (subsets will be 2D then), and [2] to specify the 3rd dimension (subsets will be 1D). Duplication has no effect, so [0,0] and [0] are the same. Also, its order has no effect. See EXAMPLE below for more.

RETURN VALUE

  • self

POSSIBLE EXCEPTIONS

  • exception is raised if ( dims.min<0 || dims.max>=self.rank ).

EXAMPLE

  • Suppose that you want to do something with 2D sub-arrays in a multi-dimension NArray. First, you include this module as follows:

    require "narray"
class NArray
   include NumRu::Misc::MD_Iterators
end

    And prepare the array if you have not (here, it is 4D):

    na = NArray.int(10,2,5,2).indgen!

    Then you do the job like this:

    na.each_subary_at_dims(0,2){ |sub|
  ...  # do whatever with sub
}

    This is equivalent to the following:

    (0...na.shape[3]).each{|j|
  (0...na.shape[1]).each{|i|
    sub = na[0..-1, i, 0..-1, j]
    ...  # do whatever with sub
  }
}

    Note that the loop must be nested 3 times when <tt>na>/tt> is a 5D array, if the latter approach is used. On the other hand, it will still require the same single loop with the former.



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# File 'lib/numru/misc/md_iterators.rb', line 62

def each_subary_at_dims( *dims )
	if dims.min<0 || dims.max>=rank
	  raise ArguemntError,"Invalid dims #{dims.inspect} for #{rank}D array"
	end

	loopdims = Array.new
	sh = Array.new
	len = 1
	(0...rank).each{|i| 
	  if !dims.include?(i)
	    loopdims.push(i) 
	    sh.push(shape[i])
	    len *= shape[i]
	  end
	}
	if loopdims.length == 0
	  yield(self)
	  return self
	end
	cs = [1]
	(1...sh.length).each{|i| cs[i] = sh[i-1]*cs[i-1]}
	idx = Array.new
	all = 0..-1
	for i in 0...len do
	  loopdims.each_with_index{|d,j| idx[d] = ( (i/cs[j])%sh[j] )}
	  dims.each{|d| idx[d] = all}
	  sub = self[ *idx ]
	  yield(sub)
	end
	self
end

#each_subary_at_dims_with_index(*dims) ⇒ Object

Like #each_subary_at_dims but the block takes two arguments: subset and the subset specifier (index).

EXAMPLE

  • Suppose the example above in #each_subary_at_dims (EXAMPLE). And suppose that you want to overwrite na with the result you get. You can do it like this:

    na.each_subary_at_dims_with_index(0,2){ |sub,idx|
  result = (sub + 10) / 2
  na[*idx] = result
}

    Here, idx is an Array to be fed in the []= or [] methods with asterisk (ungrouping).



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# File 'lib/numru/misc/md_iterators.rb', line 110

def each_subary_at_dims_with_index( *dims )
	if dims.min<0 || dims.max>=rank
	  raise ArguemntError,"Invalid dims #{dims.inspect} for #{rank}D array"
	end

	loopdims = Array.new
	sh = Array.new
	len = 1
	(0...rank).each{|i| 
	  if !dims.include?(i)
	    loopdims.push(i) 
	    sh.push(shape[i])
	    len *= shape[i]
	  end
	}
	if loopdims.length == 0
	  yield(self, false)
	  return self
	end
	cs = [1]
	(1...sh.length).each{|i| cs[i] = sh[i-1]*cs[i-1]}
	idx = Array.new
	all = 0..-1
	for i in 0...len do
	  loopdims.each_with_index{|d,j| idx[d] = ( (i/cs[j])%sh[j] )}
	  dims.each{|d| idx[d] = all}
	  sub = self[ *idx ]
	  yield(sub, idx)
	end
	self
end