MPI_TYPE_CREATE_F90_INTEGER(3)

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version 5.0.10 · 7 versions
, in ubuntu stonking

💖 MPI_Type_create_f90_integer 💖

okay bestie so we're in the Open MPI manual, section 3, and today's main character is MPI_Type_create_f90_integer — she's the one who hands you a bounded MPI integer datatype when you ask nicely. this page is everything u need to know about her, no cap ✨

🌸 NAME 🌸

MPI_Type_create_f90_integer — returns a bounded MPI integer datatype 🫶

✨ SYNTAX ✨

💅 C Syntax

#include <mpi.h>

int MPI_Type_create_f90_integer(int r, MPI_Datatype *newtype)

🎀 Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_TYPE_CREATE_F90_INTEGER (R, NEWTYPE, IERROR)
     INTEGER R, NEWTYPE, IERROR

🦋 Fortran 2008 Syntax

USE mpi_f08
MPI_Type_create_f90_integer(r, newtype, ierror)
     INTEGER, INTENT(IN) :: r
     TYPE(MPI_Datatype), INTENT(OUT) :: newtype
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

🍓 INPUT PARAMETER 🍓

  • r — your precision, in decimal digits. it's an integer, bestie. that's literally it 💖

🌈 OUTPUT PARAMETERS 🌈

  • newtype — the new data type, as a handle 🎀
  • ierror — Fortran only: the error status, and yes it's an integer 💅

👑 DESCRIPTION 👑

so the way this works: this function is how you declare KIND-parameterized INTEGER MPI datatypes. the argument gets interpreted kinda the same way the F90 function SELECTED_INT_KIND does it — r has to be a scalar integer, and it represents the level of numerical precision you want, counted in decimal digits ✨

🔥 NOTES 🔥

ngl this part matters, so pay attention 👀

It is erroneous to supply a value for r that your compiler doesn't support. like, don't do that. 💀

okay so here's the tea: the Fortran function SELECTED_INT_KIND maps a large number of r values down to a much smaller number of KIND parameters that the compiler actually supports. and KIND parameters? they are not specified by the language and they are not portable. from the language's point of view, two variables with the same base type and the same KIND parameter are equivalent — even if their KIND parameters came from totally different r arguments to SELECTED_INT_KIND. 😭

BUT. to help facilitate interoperability in a heterogeneous environment, equivalency is defined more strictly for datatypes returned by MPI_Type_create_f90_integer. the rule is: two MPI datatypes, each generated by this function, will match if and only if they have identical values for r. periodt. 👑

The interaction between the datatypes returned by this function and the external32 data representation — which is used by MPI_Pack_external, MPI_Unpack_external and many MPI_File functions — is subtle. The external32 representation of returned datatypes is as follows:

if (r > 38):
        external32 size = n/a (undefined)
else if (r > 18):
        external32 size = 16
else if (r > 9):
        external32 size = 8
else if (r > 4):
        external32 size = 4
else if (r > 2):
        external32 size = 2
else:
        external32 size = 1

If the external32 representation of a datatype is undefined, then so are the results of using that datatype in operations that require the external32 format. so be careful and do not use incompatible datatypes indirectly — like, as part of another datatype, or through a duplicated datatype — in these functions. 🙈

And if a variable is declared specifying a nondefault KIND value that wasn't obtained with SELECTED_INT_KIND (i.e., r is unknown), the only way to obtain a matching MPI datatype is to use the functions MPI_Sizeof and MPI_Type_match_size. that's the whole escape hatch, bestie 🫶

💀 ERRORS 💀

Almost all MPI routines return an error value — C routines as the return result of the function, and Fortran routines in the last argument. iykyk ✨

Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions. 😌

Open MPI includes three predefined error handlers that can be used:

  • MPI_ERRORS_ARE_FATAL — Causes the program to abort all connected MPI processes. 💀
  • MPI_ERRORS_ABORT — An error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI_Abort was called on that communicator. If called on a window or file, acts as if MPI_Abort was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process.
  • MPI_ERRORS_RETURN — Returns an error code to the application. 🎀

MPI applications can also implement their own error handlers by calling:

  • MPI_Comm_create_errhandler then MPI_Comm_set_errhandler
  • MPI_File_create_errhandler then MPI_File_set_errhandler
  • MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init
  • MPI_Win_create_errhandler then MPI_Win_set_errhandler

Note that MPI does not guarantee that an MPI program can continue past an error. so like. respect the error, fr fr 😭

See the MPI man page for a full list of MPI error codes.

See the Error Handling section of the MPI-3.1 standard for more information.

See also:

  • MPI_Pack_external
  • MPI_Sizeof
  • MPI_Type_match_size
  • MPI_Unpack_external
  • SELECTED_INT_KIND

Copyright — 2003-2026, The Open MPI Community 💜

aaaand that's the whole page bestie, you ate it, go forth and declare ur KIND-parameterized INTEGERs responsibly 👑💅

Open MPI, MPI_TYPE_CREATE_F90_INTEGER(3) — dated Sep 10, 2026, copyright 2003-2026, The Open MPI Community 🎀🦋✨

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