HPL_spreadN(3)

💖 HPL_spreadN 💖

okay bestie, welcome to HPL_spreadN(3) from the HPL Library Functions lineup — this is the one that spreads the row panel U around and forwards the current column panel. she's a real one. ✨

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🌸 NAME 🌸

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

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🎀 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 );

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🦋 DESCRIPTION 🦋

so basically, HPL_spreadN spreads the local array holding the local pieces of U, so that when this function exits, a piece of U is literally sitting in every process row. like, everybody eats. 💅

the array IPLEN tells you the number of rows of U that should be spread onto any given process row. she also probes for the presence of the column panel PBCST — and if it's a success, that panel gets forwarded. 🫶

and if PBCST is NULL on input? then this whole probing mechanism is disabled, periodt. no probing for you.

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👑 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 says whether or not the broadcast has already been completed. if it hasn't, probing will occur, and the outcome lives 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. no cap.
• N (global input) — const int — on entry, N specifies the local number of columns of U. N must be at least zero. that's the vibe check. 😤
• 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]. iykyk 🧚
• 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.

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🌈 SEE ALSO 🌈

HPL_pdlaswp01N (3).

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that's the whole page, bestie — go forth and spread that panel 💜

this iconic lil manual page is from HPL 2.2, dated February 24, 2016 — mwah, xoxo, she ate and left no crumbs 💅🎀