al_decompose.c File Reference

ArrayLib functions to decompose the domain among the MPI processes. More...

#include "al_hidden.h"

Functions
int	AL_Find_decomp_ (int sz_ptr, int mode, int *procs)
int	AL_Global_to_local_ (int sz_ptr)
int	AL_Decomp1d_ (int gdim, int lproc, int lloc, int *start, int *end)
int	AL_Decompose (int sz_ptr, int *procs, int mode)

Detailed Description

ArrayLib functions to decompose the domain among the MPI processes.

Authors

A. Malagoli (University of Chicago)

G. Muscianisi (g.mus.nosp@m.cian.nosp@m.isi@c.nosp@m.inec.nosp@m.a.it)

A. Mignone (migno.nosp@m.ne@p.nosp@m.h.uni.nosp@m.to.i.nosp@m.t)

Date

Aug 24, 2012

Function Documentation

int AL_Decomp1d_	(	int	gdim,
		int	lproc,
		int	lloc,
		int *	start,
		int *	end
	)

Decompose a 1D array, given the number of processors along the direction

Parameters

[in]	gdim	integer size of the global dimension
[in]	lproc	integer size of the number of processors along the dimension
[in]	lloc	integer location of this node along the dimension
[out]	start	integer pointer to start address for the array (C-convention)
[out]	end	integer pointer to end address for the array (C-convention)

int AL_Decompose	(	int	sz_ptr,
		int *	procs,
		int	mode
	)

Create a distributed array descriptor and compile it

Parameters

[in]	sz_ptr	integer pointer to the distributed array descriptor
[in,out]	procs	array with the processor decomposition
[in]	mode	available value: AL_AUTO_DECOMP (internal decomposition) [Only for powers of two dimensions]; AL_MPI_DECOMP (MPI decomposition); AL_USER_DECOMP (user defined)

Bug fixed on Aug 26, 2012: When the global view of the file for a staggered variable is computed, the gdims[nd] has to be computed and then passed to the function AL_Type_create_subarray.

Since gdims[nd]=s->arrdim[nd], and in s->arrdim[nd] is taking into account that the variable is staggered, we comment the line "gdims[istag]++;" because it is no more needed.

Bug fixed on Aug 26, 2012: The following "if" has been modified:

OLD version: if (s->beg[istag] == s->bg[istag]) { ldims[istag]++; }else{ starts[istag]++; }

NEW version: if (s->beg[istag] == s->bg[istag]) { }else{ starts[istag]++; ldims[istag]–; }

• "ldims[istag]++;" has been cancelled from the firt part of the if for the same motivation explaned before;
• "ldims[istag]–;" has been added in the second part of the if because in PLUTO the index of the staggered variables start from -1, while in the ArrayLib they start from 0.

Bugs fixed on Aug 26, 2012: The following if has been modified:

OLD version: if (s->beg[istag] == s->bg[istag]) { ldims[istag]++; starts[istag]–; }

NEW version: if (s->beg[istag] == s->bg[istag]) { }else{ ldims[istag]–; starts[istag]++; }

• "ldims[istag]++;" has been cancelled from the firt part of the if because when the local subarray for the MPI_Set_write_all for a staggered variable is computed, the ldims[nd] has to be computed and then passed to the function AL_Type_create_subarray. Since ldims[nd]=s->larrdim[nd], and in s->larrdim[nd] is taking into account that the variable is staggered, we remouved the line "ldims[istag]++;" because it is no more needed;
• "starts[istag]–;" has been cancelled from the first part of the if because in PLUTO the indexes for the staggered variables start locally from -1, while in ArrayLib they start from 0;
• the "else" has been added to take into account the motivation explaned in the point before.

int AL_Find_decomp_	(	int	sz_ptr,
		int	mode,
		int *	procs
	)

Find the decomposition for a distributed array given its global size and the number of nodes

Parameters

[in]	sz_ptr	integer pointer to the SZ structure
[in]	mode	mode parameter: AL_AUTO_DECOMP, AL_MPI_DECOMP, AL_USER_DECOMP
[in,out]	procs	array of processor decomposition

int AL_Global_to_local_

(

int

sz_ptr

)

Compute addresses of local portions of array from global dimensions and processor decomposition

Parameters

[in]

sz_ptr

integer pointer to SZ structure

Bug fixed on Dec 7, 2011: The lines:

if( s->isstaggered[i] == AL_TRUE ){ s->lend[i] = (end-start+1+s->lbeg[i]);}

if( s->isstaggered[i] == AL_TRUE ){ s->larrdim_gp[i] = (end-start+1+s->bg[i]+s->eg[i]+1);}

if( s->isstaggered[i] == AL_TRUE ){ s->larrdim[i] = (end-start+1+1);}

have been added to manage in the right way the correspondence among global and local indeces for staggered variables.