Centre Blaise Pascal » HPL sur GPU

.TH HPL_pdlaswp01N 3 "September 10, 2008" "HPL 2.0" "HPL Library Functions"

.SH NAME

HPL_pdlaswp01N \- Broadcast a column panel L and swap the row panel U.

.SH SYNOPSIS

\fB\&#include "hpl.h"\fR

\fB\&void\fR

\fB\&HPL_pdlaswp01N(\fR

\fB\&HPL_T_panel *\fR

\fI\&PBCST\fR,

\fB\&int *\fR

\fI\&IFLAG\fR,

\fB\&HPL_T_panel *\fR

\fI\&PANEL\fR,

\fB\&const int\fR

\fI\&NN\fR

\fB\&);\fR

.SH DESCRIPTION

\fB\&HPL_pdlaswp01N\fR

applies the  NB  row interchanges to  NN columns of the

trailing submatrix and broadcast a column panel.

A "Spread then roll" algorithm performs  the swap :: broadcast  of the

row panel U at once,  resulting in a minimal communication volume  and

a "very good"  use of the connectivity if available.  With  P  process

rows  and  assuming  bi-directional links,  the  running time  of this

function can be approximated by:

   (log_2(P)+(P-1)) * lat +   K * NB * LocQ(N) / bdwth

where  NB  is the number of rows of the row panel U,  N is the global

number of columns being updated,  lat and bdwth  are the latency  and

bandwidth  of  the  network  for  double  precision real words.  K is

a constant in (2,3] that depends on the achieved bandwidth  during  a

simultaneous  message exchange  between two processes.  An  empirical

optimistic value of K is typically 2.4.

.SH ARGUMENTS

.TP 8

PBCST   (local input/output)    HPL_T_panel *

On entry,  PBCST  points to the data structure containing the

panel (to be broadcast) information.

.TP 8

IFLAG   (local input/output)    int *

On entry, IFLAG  indicates  whether or not  the broadcast has

already been completed.  If not,  probing will occur, and the

outcome will be contained in IFLAG on exit.

.TP 8

PANEL   (local input/output)    HPL_T_panel *

On entry,  PANEL  points to the data structure containing the

panel information.

.TP 8

NN      (local input)           const int

On entry, NN specifies  the  local  number  of columns of the

trailing  submatrix  to  be swapped and broadcast starting at

the current position. NN must be at least zero.

.SH SEE ALSO

.BR HPL_pdgesv \ (3),

.BR HPL_pdgesvK2 \ (3),

.BR HPL_pdupdateNN \ (3),

.BR HPL_pdupdateTN \ (3),

.BR HPL_pipid \ (3),

.BR HPL_plindx1 \ (3),

.BR HPL_plindx10 \ (3),

.BR HPL_spreadN \ (3),

.BR HPL_equil \ (3),

.BR HPL_rollN \ (3),

.BR HPL_dlaswp00N \ (3),

.BR HPL_dlaswp01N \ (3),

.BR HPL_dlaswp06N \ (3).