dfft: Distributed FFT

FFTW + 3-D to 1-D Data Redistribution

This directory contains the implementation and tests for the FFTW MPI
transform, combined with a 1-d <--> 3-d data redistribution so that it
can be applied directly to problems requiring a 3-d data distribution

Implementation:
  distribution.c
  distribution.h

Tools:
  fp.h
    Floating point comparison functions.  

  cycle.h
    The cycle timer from FFTW, useful for comparative benchmarks.

Tests:

  test-distribution
    This test initializes the field to the value of its global
    coordinate for thorough checking of the redistribution
    functions. Checks that the data is correct are performed before
    and after each data redistribution redistribution

  test-distribution-fft
    As above but with a forward backward fft.

  test-delta-function
    This test initializes the field to a delta function centered
    and performs forward and backward transforms, checking the
    data is correct before and after each data redistribution
    or transform.

  test-timing
    This test times the combined redistribution and transform.

  test-solver
    A test stand-alone implementation of the Poisson solver.