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/* -*- mode: c; tab-width: 4; indent-tabs-mode: n; c-basic-offset: 4 -*-
*
* $Id: gmx_parallel_3dfft.h,v 1.1.2.2 2005/09/30 13:15:51 lindahl Exp $
*
* Gromacs Copyright (c) 1991-2005
* David van der Spoel, Erik Lindahl, University of Groningen.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* To help us fund GROMACS development, we humbly ask that you cite
* the research papers on the package. Check out http://www.gromacs.org
*
* And Hey:
* Gnomes, ROck Monsters And Chili Sauce
*/
#ifndef _gmx_parallel_3dfft_h_
#define _gmx_parallel_3dfft_h_
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#ifdef GMX_MPI
#include "types/simple.h"
#include "gmxcomplex.h"
#include "gmx_fft.h"
/* We NEED MPI here. */
#include <mpi.h>
typedef struct gmx_parallel_3dfft *
gmx_parallel_3dfft_t;
/*! \brief Initialize parallel MPI-based 3D-FFT.
*
* This routine performs real-to-complex and complex-to-real parallel 3D FFTs,
* but not complex-to-complex.
*
* The routine is optimized for small-to-medium size FFTs used for PME and
* PPPM algorithms, and do allocate extra workspace whenever it might improve
* performance.
*
* \param pfft_setup Pointer to parallel 3dfft setup structure, previously
* allocated or with automatic storage.
* \param ngridx Global number of grid cells in the x direction. Must be
* divisible by the number of nodes.
* \param ngridy Global number of grid cells in the y direction. Must be
* divisible by the number of nodes.
* \param ngridz Global number of grid cells in the z direction.
* \param comm MPI communicator, must have been initialized.
*
* \return 0 or a standard error code.
*/
int
gmx_parallel_3dfft_init (gmx_parallel_3dfft_t * pfft_setup,
int ngridx,
int ngridy,
int ngridz,
MPI_Comm comm);
/*! \brief Get direct space grid index limits
*
* The z dimension is never distributed. In the direct space, the x dimension
* is distributed over nodes, and after the real-to-complex FFT we work with
* a transposed grid where the y dimension is partitioned over nodes.
*
* The order is determined from the rank in the communicator used at
* initialization.
*/
int
gmx_parallel_3dfft_limits(gmx_parallel_3dfft_t pfft_setup,
int * local_x_start,
int * local_nx,
int * local_y_start,
int * local_ny);
int
gmx_parallel_transpose(t_complex * data,
t_complex * work,
int nx,
int ny,
int local_x_start,
int local_nx,
int local_y_start,
int local_ny,
int nelem,
MPI_Comm comm);
/*! \brief Perform forward parallel MPI FFT.
*
* Direction is either GMX_FFT_REAL_TO_COMPLEX or GMX_FFT_COMPLEX_TO_REAL.
*
* If input and output arrays are separate there is no packing to consider.
* Input is simply nx*ny*nz in real, and output ny*nx*nzc in complex.
*
* In they are identical we need to make sure there is room for the complex
* (length nzc=nz/2+1) in the array, so the _real_ space dimensions is
* always padded to nzc*2.
* In this case, the real dimensions are nx*ny*(nzc*2) while the complex
* dimensions is ny*nx*nzc (of type complex).
*
* Note that the X and Y dimensions are transposed in the reciprocal space
* to avoid extra communication!
*/
int
gmx_parallel_3dfft(gmx_parallel_3dfft_t pfft_setup,
enum gmx_fft_direction dir,
void * in_data,
void * out_data);
/*! \brief Release all data in parallel fft setup
*
* All temporary storage and FFT plans are released. The structure itself
* is not released, but the contents is invalid after this call.
*
* \param pfft_setup Parallel 3dfft setup.
*
* \return 0 or a standard error code.
*/
int
gmx_parallel_3dfft_destroy(gmx_parallel_3dfft_t pfft_setup);
#endif /* GMX_MPI */
#endif /* _gmx_parallel_3dfft_h_ */
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