MPI_PCONTROL(3)

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💖 MPI_PCONTROL(3) — the Open MPI glow-up ✨

okay bestie, sit down, hydrate, because today we're talking about MPI_Pcontrol from the Open MPI manual, and it is literally the "controls profiling" girlie of the MPI world. no cap. 💅

🌸 NAME 🌸

MPI_Pcontrol — Controls profiling. that's it, that's the whole job, she's a vibe curator for your profile output 🎀

✨ SYNTAX ✨

🦋 C Syntax

#include <mpi.h>

int MPI_Pcontrol(const int level, ... )

🦋 Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_PCONTROL(LEVEL)
     INTEGER LEVEL

🦋 Fortran 2008 Syntax

USE mpi_f08
MPI_Pcontrol(level)
     INTEGER, INTENT(IN) :: level

🍓 INPUT PARAMETER 🍓

  • level — the profiling level. that's the whole input, she's low-maintenance 💜

👑 DESCRIPTION 👑

okay so here's the tea: the MPI libraries themselves literally do nothing with this routine. they just return immediately back to your user code. like, "not my department, bestie" 🙈 but — and this is the main character moment — having calls to this routine in your code means a profiling package</> can be explicitly called by the user. so the call site is the whole point. iykyk.

and because MPI has zero control over how the profiling code is implemented, we literally cannot specify precisely what semantics calls to MPI_Pcontrol will give you. this vagueness extends to the number of arguments to the function, and their datatypes. yeah. it's giving "undefined but make it fashion" 😭

<b>HOWEVER</b> — so that user codes can at least be somewhat portable across different profiling libraries, we request the following meanings for certain values of level:

  • level==0 — Profiling is disabled. 🔇
  • level==1 — Profiling is enabled at a normal default level of detail. 🔛
  • level==2 — Profile buffers are flushed. (This may be a no-op in some profilers). 🚽✨
  • All other values of level have profile library-defined effects and additional arguments. 👀 (mystery box energy)

we also request that the default state after MPI_Init has been called is for profiling to be enabled at the normal default level — i.e., as if MPI_Pcontrol had just been called with the argument 1. this is the slay part: it means users can link with a profiling library and get profile output without having to modify their source code at all. zero edits, all receipts. 🔥

and the provision of MPI_Pcontrol as a no-op in the standard MPI library? iconic. it lets users modify their source code to obtain more detailed profiling information, but still be able to link exactly the same code against the standard MPI library. best of both worlds, periodt. 💅

💀 NOTES 💀

  • This routine provides a common interface for profiling control. The interpretation of level and any other arguments is left to the profiling library. 🤝
  • This function does not return an error value. Consequently, the result of calling it before MPI_Init or after MPI_Finalize is undefined. so like… don't do that. fr fr. that's the "do not perceive me" zone 🫠
⚠️ real talk bestie: no error value means no safety net, and calling it before MPI_Init or after MPI_Finalize is undefined behavior. keep your calls inside the init/finalize window and you're golden 💛

2003-2026, The Open MPI Community

and that's the whole page, bestie 🫶 this was MPI_PCONTROL(3) from the Open MPI manual, dated Sep 10, 2026. go forth, profile responsibly, and remember: link the same code, get the extra detail ✨🎀🦋

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