Module: Narray::Convolve

Defined in:
lib/narray/convolve.rb,
lib/narray/convolve/version.rb

Constant Summary collapse

VERSION = 
"0.2.1"

Class Method Summary collapse

Class Method Details

.convolve(n, m, mode = :full) ⇒ Numo::DFloat

Narray::Convolve is similar to numpy.convolve, but with a different order of second arguments.

Examples:

Narray::Convolve

require "narray/convolve"
n = Numo::DFloat[1,2,3]
m = Numo::DFloat[0,1,0.5].reverse
Narray::Convolve.convolve(n, m, :same)
# => [1, 2.5, 4]

or 

Narray::Convolve.convolve([1,2,3], [0,1,0.5].reverse, :same)
# => [1, 2.5, 4]

In case of numpy.convolve
>>> numpy.convolve([1,2,3],[0,1,0.5], 'same')
array([1. , 2.5, 4. ])



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# File 'lib/narray/convolve.rb', line 38

def convolve(n, m, mode = :full)
  case n
  when Array
    n = Numo::DFloat.cast(n)
  when Numo::DFloat
    # ok
  else
    raise ArgumentError, "not Numo::DFloat: #{n.inspect[0..48]}"
  end

  case m
  when Array
    m = Numo::DFloat.cast(m)
  when Numo::DFloat
    # ok
  else
    raise ArgumentError, "not Numo::DFloat: #{n.inspect[0..48]}"
  end

  n_size = n.size
  m_size = m.size
  zero_size = m_size - 1
  out_size = zero_size + n_size
  n_end = out_size - 1
  work_size = out_size + zero_size

  out = Numo::DFloat.zeros(out_size)
  work = Numo::DFloat.zeros(work_size)
  work[zero_size..n_end].store(n[true])

  work_size.times do |i|
    w = i + zero_size
    if w < work_size
      out[i] = work[i..w].mulsum(m)
    end
  end

  case mode
  when :full
    # full: (N+M-1)    
    ans = out[true]
  when :same
    # same: [M,N].max
    s = (m_size / 2.0).round - 1
    e = s + n_size
    ans = out[s...e]
  when :valid
    # valid: [M,N].max - [M,N].min + 1
    s = zero_size
    e = m_size
    ans = out[s..-e]
  end
  ans
end