MPI_TYPE_CONTIGUOUS(3)

💅 MPI_Type_contiguous — creates a contiguous datatype ✨

okay so bestie, welcome to Open MPI, section 3 of the manual — this is the MPI_Type_contiguous page and honestly? it's a cutie. it's the simplest datatype constructor and it still ate. let's get into it 🎀

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🌸 SYNTAX 🌸

✨ C Syntax

#include <mpi.h>

int MPI_Type_contiguous(int count, MPI_Datatype oldtype,
     MPI_Datatype *newtype)

✨ Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_TYPE_CONTIGUOUS(COUNT, OLDTYPE, NEWTYPE, IERROR)
     INTEGER COUNT, OLDTYPE, NEWTYPE, IERROR

✨ Fortran 2008 Syntax

USE mpi_f08
MPI_Type_contiguous(count, oldtype, newtype, ierror)
     INTEGER, INTENT(IN) :: count
     TYPE(MPI_Datatype), INTENT(IN) :: oldtype
     TYPE(MPI_Datatype), INTENT(OUT) :: newtype
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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🫶 INPUT PARAMETERS 🫶

• count — the replication count, and it's a nonnegative integer bestie, so no negative vibes allowed 💀
• oldtype — the old datatype (handle). the og. the blueprint 👑

🎀 OUTPUT PARAMETERS 🎀

• newtype — the new datatype (handle). the glow-up 💖
• ierror — Fortran only: error status (integer).

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🦋 DESCRIPTION 🦋

so. MPI_Type_contiguous is literally the simplest datatype constructor in the game — it lets you replicate a datatype into contiguous locations. iconic behaviour, no notes ✨

newtype is the datatype you get by concatenating count copies of oldtype. and the way concatenation works? it uses the extent of oldtype as the size of each concatenated copy. that's the whole vibe check. iykyk 💅

Example, because we love a concrete moment: let oldtype have the type map {(double, 0), (char, 8)}, with extent 16, and let count = 3. then the type map of the datatype returned by newtype is

{(double, 0), (char, 8), (double, 16), (char, 24),
(double, 32), (char, 40)];

i.e., alternating double and char elements, with displacements 0, 8, 16, 24, 32, 40. look at that pattern, she's gorgeous 🌈

In general (and this is the part to screenshot, bestie 📸), assume the type map of oldtype is

{(type(0), disp(0)),...,(type(n-1), disp(n-1))},

with extent ex. then newtype has a type map with count times n entries defined by:

{(type(0), disp(0)), ...,(type(n-1), disp(n-1)),
(type(0), disp(0) + ex), ...,(type(n-1),
disp(n-1) + ex), ...,(type(0), disp(0) + ex * (count - 1)),
...,(type(n-1), disp(n-1) + ex * (count - 1))}.

for more info about derived datatypes, go read the Datatypes chapter in the MPI Standard. it's giving required reading but make it cute 🧚

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💀 ERRORS 💀

almost all MPI routines return an error value — C routines hand it back as the return result of the function, and Fortran routines put it in the last argument. so keep an eye out, fr fr 👀

before that error value gets returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. and if there's no communication object 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. and that 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. that's just how it is 🫠

Open MPI includes three predefined error handlers you can use:

• MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes. dramatic? yes. effective? also yes 💀
• 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, it aborts only the local process.
• MPI_ERRORS_RETURN — returns an error code to the application. the chill one 🍓

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… don't just keep going and hope for the best, bestie 😭

see the MPI man page for a full list of MPI error codes — and the Error Handling section of the MPI-3.1 standard for more information. it's all there, i promise 🫶

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👑 COPYRIGHT 👑

2003-2026, The Open MPI Community

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and that's the page, bestie!! 🎀 no cap, you're now like lowkey an expert on contiguous datatypes. this was MPI_TYPE_CONTIGUOUS(3) from Open MPI, dated Sep 11, 2026 — go forth and concatenate, queen 👑💖