MPI_TYPE_CONTIGUOUS(3)

👑 MPI_TYPE_CONTIGUOUS 👑

okay so bestie, gather round, because this is the Open MPI manual page situation for MPI_Type_contiguous — and yes, the manual name is literally MPI_TYPE_CONTIGUOUS (all caps, screaming, iconic). ✨

What does it do? It creates a contiguous datatype. That's the whole vibe. Let's get into it 💅

---

✨ 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

---

🌸 INPUT PARAMETERS 🌸

• count — the replication count, and no cap, it has to be a nonnegative integer. 🫶
• oldtype — the old datatype (handle). the before picture 💅

---

🎀 OUTPUT PARAMETERS 🎀

• newtype — the new datatype (handle). the after picture, slay ✨
• ierror — Fortran only: error status (integer).

---

🦋 DESCRIPTION 🦋

okay so, the simplest datatype constructor out of the whole crew is MPI_Type_contiguous, and all it does is let you replicate a datatype into contiguous locations. lowkey elegant, highkey useful. 💖

newtype is the datatype you get by concatenating count copies of oldtype. and the way the concatenation works is — it uses the extent of oldtype as the size of the concatenated copies. no cap.

Example: 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. the pattern? obsessed. 😭

in general, assume that 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))}.

want more lore on derived datatypes? go read the Datatypes chapter in the MPI Standard at https://www.mpi-forum.org/docs/. 🧚

---

💀 ERRORS 💀

almost every MPI routine returns an error value, bestie. C routines hand it back as the return result of the function, and Fortran routines put it in the last argument. that's just how the family works.

before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) gets called. and 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
• the info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple.

and 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. periodt. 🔥

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. read that again. it's giving no promises, fr fr. 😭

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

and see the Error Handling section of the MPI-3.1 standard for more information. iykyk 📚

---

🫶 Copyright 🫶

2003-2026, The Open MPI Community

---

and that's the whole page, bestie — brought to you by Open MPI, dated Sep 10, 2026, page MPI_TYPE_CONTIGUOUS(3). now go build a datatype and be the main character of your own type map 💜🦋✨