# HPL_spreadN man page

HPL_spreadN — Spread row panel U and forward current column panel.

## Synopsis

**#include "hpl.h"**

**void HPL_spreadN( HPL_T_panel *** *PBCST*, **int *** *IFLAG*, **HPL_T_panel *** *PANEL*, **const enum HPL_SIDE** *SIDE*, **const int** *N*, **double *** *U*, **const int** *LDU*, **const int** *SRCDIST*, **const int *** *IPLEN*, **const int *** *IPMAP*, **const int *** *IPMAPM1* **);**

## Description

**HPL_spreadN** spreads the local array containing local pieces of U, so that on exit to this function, a piece of U is contained in every process row. The array IPLEN contains the number of rows of U, that should be spread on any given process row. This function also probes for the presence of the column panel PBCST. In case of success, this panel will be forwarded. If PBCST is NULL on input, this probing mechanism will be disabled.

## Arguments

- PBCST (local input/output) HPL_T_panel *
On entry, PBCST points to the data structure containing the panel (to be broadcast) information.

- 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.

- PANEL (local input/output) HPL_T_panel *
On entry, PANEL points to the data structure containing the panel (to be spread) information.

- SIDE (global input) const enum HPL_SIDE
On entry, SIDE specifies whether the local piece of U located in process IPMAP[SRCDIST] should be spread to the right or to the left. This feature is used by the equilibration process.

- N (global input) const int
On entry, N specifies the local number of columns of U. N must be at least zero.

- U (local input/output) double *
On entry, U is an array of dimension (LDU,*) containing the local pieces of U.

- LDU (local input) const int
On entry, LDU specifies the local leading dimension of U. LDU should be at least MAX(1,IPLEN[nprow]).

- SRCDIST (local input) const int
On entry, SRCDIST specifies the source process that spreads its piece of U.

- IPLEN (global input) const int *
On entry, IPLEN is an array of dimension NPROW+1. This array is such that IPLEN[i+1] - IPLEN[i] is the number of rows of U in each process before process IPMAP[i], with the convention that IPLEN[nprow] is the total number of rows. In other words IPLEN[i+1] - IPLEN[i] is the local number of rows of U that should be moved to process IPMAP[i].

- IPMAP (global input) const int *
On entry, IPMAP is an array of dimension NPROW. This array contains the logarithmic mapping of the processes. In other words, IPMAP[myrow] is the absolute coordinate of the sorted process.

- IPMAPM1 (global input) const int *
On entry, IPMAPM1 is an array of dimension NPROW. This array contains the inverse of the logarithmic mapping contained in IPMAP: For i in [0.. NPROW) IPMAPM1[IPMAP[i]] = i.

## See Also

**HPL_pdlaswp01N** (3).