SHMEM_GET64(3)

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version 5.0.10 · 4 versions
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SHMEM_GET64 💖 (aka the whole shmem_*_get girlie squad)

okay bestie, you opened the shmem_get family manual page in Open MPI, and honestly? iconic. it's giving "one-trip data heist from another PE". let's get into it 🦋

🌸 NAME

This one page covers a whole clique of routines. every single one transfers data from a specified processing element (PE):

✨ SYNOPSIS ✨

🎀 C or C++

#include <mpp/shmem.h>

void shmem_get32(void *target, const void *source,
  size_t len, int pe)

void shmem_get64(void *target, const void *source,
  size_t len, int pe)

void shmem_get128(void *target, const void *source,
  size_t len, int pe)

void shmem_getmem(void *target, const void *source,
  size_t len, int pe)

void shmem_int_get(int *target, const int *source,
  size_t len, int pe)

void shmem_double_get(double *target, const double *source,
  size_t len, int pe)

void shmem_float_get(float *target, const float *source,
  size_t len, int pe)

void shmem_long_get(long *target, const long *source,
  size_t len, int pe)

void shmem_longdouble_get(long double *target,
  const long double *source, size_t len, int pe)

void shmem_longlong_get(long long *target,
  const long long *source, size_t len, int pe)

void shmem_short_get(short *target,
  const short *source, size_t len, int pe)

🌈 Fortran

INCLUDE "mpp/shmem.fh"

INTEGER len, pe

CALL SHMEM_CHARACTER_GET(target, source, len, pe)

CALL SHMEM_COMPLEX_GET(target, source, len, pe)

CALL SHMEM_DOUBLE_GET(target, source, len, pe)

CALL SHMEM_GET4(target, source, len, pe)

CALL SHMEM_GET8(target, source, len, pe)

CALL SHMEM_GET32(target, source, len, pe)

CALL SHMEM_GET64(target, source, len, pe)

CALL SHMEM_GET128(target, source, len, pe)

CALL SHMEM_GETMEM(target, source, len, pe)

CALL SHMEM_INTEGER_GET(target, source, len, pe)

CALL SHMEM_LOGICAL_GET(target, source, len, pe)

CALL SHMEM_REAL_GET(target, source, len, pe)

💅 DESCRIPTION 💅

so what do these bad boys actually do? the shmem_get routines transfer nelems elements of the data object at address source on the remote PE pe, over to the data object at address target on the local PE. and here's the main character detail: they return after the data has been copied to address target on the local PE. no vibes-based timing, it's done when it's done. periodt ✋

🧚 the arguments, bestie

  • target — the local data object that's getting updated. glow-up destination 💖
  • source — the data object on the PE identified by pe that holds the data to be copied. and btw? this data object must be remotely accessible. no exceptions, no cap.
  • len — the number of elements in the target and source arrays. len must be of type integer. in Fortran it has to be a constant, variable, or array element of default integer type.
  • pe — the PE number of the remote PE. pe must be of type integer. in Fortran it has to be a constant, variable, or array element of default integer type.

🔥 the typing constraints (read this part fr fr)

the target and source data objects must conform to typing constraints, and they go a lil something like this:

  • shmem_getmem — Fortran: any noncharacter type. C: any data type. len is scaled in bytes.
  • shmem_get4, shmem_get32 — any noncharacter type that has a storage size equal to 32 bits.
  • {shmem_get8, shmem_get64} — any noncharacter type that has a storage size equal to 64 bits.
  • shmem_get128 — any noncharacter type that has a storage size equal to 128 bits.
  • shmem_short_get — elements of type short.
  • shmem_int_get — elements of type int.
  • shmem_long_get — elements of type long.
  • shmem_longlong_get — elements of type long long.
  • shmem_float_get — elements of type float.
  • shmem_double_get — elements of type double.
  • shmem_longdouble_get — elements of type long double.
  • SHMEM_CHARACTER_GET — elements of type character. len is the number of characters to transfer. the actual character lengths of the source and target variables are ignored (yes, ignored, she said what she said).
  • SHMEM_COMPLEX_GET — elements of type complex of default size.
  • SHMEM_DOUBLE_GET — (Fortran) elements of type double precision.
  • SHMEM_INTEGER_GET — elements of type integer.
  • SHMEM_LOGICAL_GET — elements of type logical.
  • SHMEM_REAL_GET — elements of type real.
if you're using Fortran, data types must be of default size. like, a real variable has to be declared as REAL, REAL*4, or REAL(KIND=4). that's the rule, bestie, I don't make 'em 💅

🦋 NOTES 🦋

see intro_shmem(3) for a definition of the term remotely accessible. iykyk.

⭐ EXAMPLES ⭐

okay consider this simple little Fortran example, she's cute:

PROGRAM REDUCTION
  REAL VALUES, SUM
  COMMON /C/ VALUES
  REAL WORK

  CALL START_PES(0) ! ALLOW ANY NUMBER OF PES
  VALUES = MY_PE() ! INITIALIZE IT TO SOMETHING
  CALL SHMEM_BARRIER_ALL
  SUM = 0.0
  DO I = 0,NUM_PES()-1
    CALL SHMEM_REAL_GET(WORK, VALUES, 1, I)
    SUM = SUM + WORK
  ENDDO
  PRINT *, 'PE ', MY_PE(), ' COMPUTED SUM=', SUM
  CALL SHMEM_BARRIER_ALL
END

👑 See also

intro_shmem(3) shmem_put(3) shmem_iget(3) shmem_quiet(3)

2003-2026, The Open MPI Community

and that's the whole page, bestie — this lore dropped in the Open MPI manual, dated Sep 10, 2026, and it was SHMEM_GET64(3) coded by the Open MPI girlies, 2003-2026. slay, stay remotely accessible, and go get those elements 💖✨🫶

📦 where this page comes from