CONTEXT(3PVM)

💖 CONTEXT(3PVM) — pvm_newcontext, pvm_setcontext, pvm_freecontext, pvm_getcontext 💖

okay bestie, gather round, because this is the context page from PVM Version 3.4 and honestly? it's giving "the group chat has multiple threads and you keep replying in the wrong one" energy. let's fix that. ✨

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🌸 NAME 🌸

pvm_newcontext, pvm_setcontext, pvm_freecontext, pvm_getcontext — bestie these four do exactly what their names say: request a brand new context, switch context, free a context you're done with, and ask "wait, which context am I in right now?" respectively. 💅

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🦋 SYNOPSIS 🦋

C vibes:

int ctx = pvm_newcontext( void )
int old_ctx = pvm_setcontext( int new_ctx )
int info = pvm_freecontext( ctx )
int ctx = pvm_getcontext( void )

Fortran vibes:

call pvmfnewcontext( ctx )
call pvmfsetcontext( new_ctx, old_ctx )
call pvmffreecontext( ctx, info )
call pvmfgetcontext( ctx )

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🎀 PARAMETERS 🎀

• ctx — the context value, the moment, the vibe. 💫
• new_ctx — the new context value you're sliding into.
• old_ctx — the prior context value, aka where you came from, no cap.
• info — the result code. it tells you how it went. 👑

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👑 DESCRIPTION 👑

so. the context functions hand you a system-wide unique context and the tools to mess with it. iconic behavior, honestly.

contexts are the whole reason communicating tasks can automatically tell messages apart based on the context they were sent in. which means: a message sent in context A by the sender must be received in context A by the recipient. the sender can send in any context they want, go off. but a recipient will not accept a message that was sent in a context different from its own. it's giving strict door policy. 🚪

one classic use for contexts? library routines. with contexts, a library routine's inter-communication can be logically separated from your user application's inter-communication. translation: nobody accidentally receives somebody else's messages anymore. the drama? avoided. 🙈

spawned tasks inherit the spawn-time context of their parent. and existing PVM applications keep working totally unchanged on the default context. no migration arc needed. 🫶

here's the four functions doing their thing:

• pvm_newcontext returns a newly allocated context. but heads up bestie — this new context is not yet active. it's allocated, it's not live. 💀
• pvm_setcontext changes the current context from old_ctx to new_ctx. boom, you're in the new one.
• pvm_freecontext frees ctx so it may be reused. and listen — contexts are a system resource that will be exhausted if you don't recycle them. not recycling is not cute. recycle your contexts. 🌈
• pvm_getcontext returns the current context of the requesting task. the "who am I" of it all. 🪞

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✨ EXAMPLES ✨

parent task with context:

/* parent task with context */
     int cc, context0, context1;
     char buf[25];

     context0 = pvm_getcontext();       /*  get my current context */
     context1 = pvm_newcontext();       /*  get a new context */
     pvm_setcontext(context1);          /*  set my context to new context */
     printf("My context is: %d", context1);
     pvm_spawn("child", (char**)0, PvmTaskDefault, "", 1, &tid);
     cc = pvm_recv(-1, -1);             /*  receive message from child - in context1 */
     pvm_upkstr(buf);
     printf("%s", buf);
     pvm_setcontext(context0);          /*  reset my context to my original context0 */

child task with context — child inherits parent's context as default:

/* child task with context - child inherits parent's context as default */
     int context;
     int ptid;
     char buf[25];

     ptid = pvm_parent();
     context = pvm_getcontext();        /*  get my current context */
     sprintf(buf, "Greetings from child who's context is: %d.", context);
     pvm_initsend(PvmDataDefault);
     pvm_pkstr(buf);
     pvm_send(ptid, 1);

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😭 ERRORS 😭

only system resource errors will be returned, bestie — because the context programs themselves do not generate errors. they're chill like that. zero drama, zero self-made problems. 🧚

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🔥 SEE ALSO 🔥

literally nothing here. the SEE ALSO list is empty. no cross-references, no cousins, no neighbors. this page is an only child and it's thriving. 👑

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and that's the whole page, periodt. this was PVM Version 3.4, dated 8 April, 1997 — so yes, technically this manual is older than most of us, and it still ate. 💖✨🎀🦋🌸💅🫶