MPI_TYPE_CREATE_F90_COMPLEX(3)

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version 5.0.10 · 7 versions
, in ubuntu stonking

✨ MPI_TYPE_CREATE_F90_COMPLEX ✨

okay bestie, welcome to the Open MPI manual, and today's episode is MPI_Type_create_f90_complex — literally the girl whose whole job is handing you a bounded MPI complex datatype 🫶

🌸 NAME 🌸

MPI_Type_create_f90_complex — returns a bounded MPI complex datatype 💖

📜 SYNTAX 📜

C Syntax

#include <mpi.h>

int MPI_Type_create_f90_complex(int p, int r,
     MPI_Datatype *newtype)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_TYPE_CREATE_F90_COMPLEX (P, R, NEWTYPE, IERROR)
     INTEGER P, R, NEWTYPE, IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_Type_create_f90_complex(p, r, newtype, ierror)
     INTEGER, INTENT(IN) :: p, r
     TYPE(MPI_Datatype), INTENT(OUT) :: newtype
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

💌 INPUT PARAMETERS 💌

  • p — precision, in decimal digits (integer). like, how many digits do you want, girl ✨
  • r — decimal exponent range (integer). how far up and down the exponents can go 💅

🎀 OUTPUT PARAMETERS 🎀

  • newtype — the new data type (handle). the fresh new datatype, hot off the press 👑
  • ierror — Fortran only: error status (integer). no cap 🙈

🦋 DESCRIPTION 🦋

So basically this function is your way to declare KIND-parameterized COMPLEX MPI datatypes. the arguments get interpreted kind of the same way the F90 function SELECTED_REAL_KIND does it — they're siblings fr fr.

The parameters p and r must be scalar integers. p is the level of numerical precision you're asking for, in decimal digits. r says how big a range of exponents you want: the returned datatype will have at least one exponent between +r and -r (inclusive). inclusive bestie, don't forget 💖

Either p or r, but not both, may be omitted from calls to SELECTED_REAL_KIND. Same energy here: either argument to MPI_Type_create_f90_complex may be set to MPI_UNDEFINED. periodt.

📝 NOTES 📝

it is erroneous to supply values for p and r that the compiler doesn't support. like, don't do it. the compiler will not be slaying with you on that one 💀

The Fortran function SELECTED_REAL_KIND maps a large number of (p,r) pairs down to a much smaller number of KIND parameters that the compiler actually supports. And here's the tea: KIND parameters are not specified by the language and are not portable. From the language's point of view, variables with the same base type and the same KIND parameter are equivalent — even if their KIND parameters came from totally different (p,r) arguments to SELECTED_REAL_KIND. iconic chaotic behaviour tbh.

But — to help with interoperability in a heterogeneous environment, equivalency is more strictly defined for datatypes returned by MPI_Type_create_f90_complex. Two MPI datatypes, each generated by this function, will match if and only if they have identical values for both p and r. no vibes-based matching here, we need receipts 🌸

The interaction between the datatypes returned by this function and the external32 data representation — the one 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 (p > 33) and/or (r > 4931):
        external32 size = n/a (undefined)
else if (p > 15) and/or (r > 307):
        external32 size = 32
else if (p > 6) and/or (r > 37):
        external32 size = 16
else:
        external32 size = 8

If the external32 representation of a datatype is undefined, so are the results of using that datatype in operations that require the external32 format. so like — care should be taken not to use incompatible datatypes indirectly, e.g., as part of another datatype or through a duplicated datatype, in these functions. that's the sneaky route and it will not end well 😭

If a variable is declared specifying a nondefault KIND value that was not obtained with SELECTED_REAL_KIND (i.e., p and/or r are 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, there is no other door 🚪✨

💀 ERRORS 💀

Almost all MPI routines return an error value; C routines return it as the return result of the function, and Fortran routines put it in the last argument.

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 you can use:

  • 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, it 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. like, that's just the rules 🙈

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_REAL_KIND

Copyright 2003-2026, The Open MPI Community

and that's the whole page, bestie 💖 thank you for coming to my TED talk, this was MPI_TYPE_CREATE_F90_COMPLEX(3) from Open MPI, dated Sep 10, 2026 🎀🦋✨ slay, go forth and declare your complex datatypes responsibly 💅

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