MPI_TYPE_VECTOR(3)

📦
version 5.0.10 · 7 versions
, in ubuntu stonking

✨ NAME ✨

MPI_Type_vector — Creates a vector (strided) datatype.

okay so real talk bestie, this is page MPI_TYPE_VECTOR(3) from the Open MPI manual, and it's genuinely one of the most useful datatype constructors in the whole MPI lineup 💅 it's giving "I want the same little chunk of memory over and over, but spaced out" and honestly? iconic.

🎀 SYNTAX 🎀

C Syntax

#include <mpi.h>

int MPI_Type_vector(int count, int blocklength, int stride,
     MPI_Datatype oldtype, MPI_Datatype *newtype)

Fortran Syntax

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

Fortran 2008 Syntax

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

🍓 INPUT PARAMETERS 🍓

  • count — how many blocks you want (nonnegative integer, no negatives babe).
  • blocklength — how many elements live inside each block (nonnegative integer).
  • stride — how many elements sit between the start of each block (integer — yes this one can be negative, hold that thought).
  • oldtype — the old datatype you're building on (handle).

💖 OUTPUT PARAMETERS 💖

  • newtype — the shiny new datatype (handle). Your baby. Your creation. 🫶
  • ierror — Fortran only: error status (integer).

🦋 DESCRIPTION 🦋

So MPI_Type_vector is a general constructor, and what it does is let you replicate a datatype into locations made of equally spaced blocks. Each block is built by concatenating the same number of copies of the old datatype. And the spacing between blocks? It's a multiple of the extent of the old datatype. periodt.

Example 1: Assume, again, that oldtype has type map {(double, 0), (char, 8)}, with extent 16. A call to MPI_Type_vector(2, 3, 4, oldtype, newtype) will create the datatype with type map

{(double, 0), (char, 8), (double, 16), (char, 24),
(double, 32), (char, 40),
(double, 64), (char, 72),
(double, 80), (char, 88), (double, 96), (char, 104)}

That is, two blocks with three copies each of the old type, with a stride of 4 elements (4 x 16 bytes) between the blocks. slay.

Example 2: A call to MPI_Type_vector(3, 1, -2, oldtype, newtype) will create the datatype

{(double, 0), (char, 8), (double, -32), (char, -24),
(double, -64), (char, -56)}

(see, told you the stride could go negative — negative offsets are not a glitch, they're a feature 💀)

In general, assume that oldtype has type map

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

with extent ex. Let bl be the blocklength. The newly created datatype has a type map with count x bl x n entries:

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

A call to MPI_Type_contiguous(count, oldtype, newtype) is equivalent to a call to MPI_Type_vector(count, 1, 1, oldtype, newtype), or to a call to MPI_Type_vector(1, count, n, oldtype, newtype), n arbitrary. the way those all collapse into each other is lowkey beautiful 😭

😭 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.

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. (yeah, everybody. the whole friend group. 💀)
  • 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… don't just keep vibing after an error and assume it's fine, bestie, 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_Type_create_hvector
  • MPI_Type_hvector

Copyright — 2003-2026, The Open MPI Community.

okay that's the whole page, no cap 💖 this was MPI_TYPE_VECTOR(3) from the Open MPI manual, stamped Sep 10, 2026, and you absolutely ate that. go forth and build your strided datatypes, main character 🌈✨👑

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