CONTEXT(3PVM)

okay bestie, sit DOWN, because we're talking about CONTEXT(3PVM) — the PVM Version 3.4 era context functions — and honestly? they ate. 🫶

✨ NAME ✨

pvm_newcontext, pvm_setcontext, pvm_freecontext, pvm_getcontext — they ask for a brand-new context, swap your context, free a context you're done with, and tell you what context you're currently in, respectively. Four little icons, one big vibe. 💅

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🌸 SYNOPSIS 🌸

C girlies, come get your function signatures:

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

Fortran besties, this one's for you:

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

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🎀 PARAMETERS 🎀

• ctx — a context value. that's it, that's the whole girl. ✨
• new_ctx — the new context value you wanna slide into.
• old_ctx — the context value from before, the ex, the previous era.
• info — the result code. it's giving receipts. 🧾

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💜 DESCRIPTION 💜

So the context functions hand you a system-wide unique context plus all the tools to mess with it. iconic behavior, no notes.

Contexts let communicating tasks automatically tell messages apart based on the context they were sent in. so like — a message sent in context A by the sender must be received in context A by the recipient. sender can send in literally any context it wants, slay. but a recipient will NOT accept a message that was sent in a context different from its own. it's giving boundaries, and honestly? respect. 🚫

One super common use is with library routines. using contexts, library-routine inter-communication can be logically separated from the user's application inter-communication. which means nobody accidentally receives each other's messages like a group chat with the wrong tab open. 😭

Spawned tasks inherit the spawn-time context of their parent. and existing PVM applications? they work unchanged using the default context. backwards compatible queen. 👑

Now the four functions, one by one:

• pvm_newcontext returns a newly allocated context. BUT — plot twist — this new context is not yet active. it's allocated, not activated. it's in its soft launch era. 🙈
• pvm_setcontext changes the current context from old_ctx to new_ctx. glow up complete.
• pvm_freecontext frees ctx so that it may be reused. and this one matters: contexts are a system resource that will be exhausted if you don't recycle them. so free your contexts, bestie, it's not a suggestion, it's self-care. 🫶
• pvm_getcontext returns the current context of the requesting task. a mirror, but for contexts. 🪞

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🔥 EXAMPLES 🔥

Parent task with context — watch her serve:

/* 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, so she's literally born with it:

/* 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, because the context programs themselves do not generate errors. they're unproblematic. they have never once been the drama. 💀

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🌈 SEE ALSO 🌈

nothing else listed here, bestie — this page is a solo act and she knows it. ⭐

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and that's the whole page, mwah 💖

cute little sign-off for the girlies who read to the bottom: this one came from PVM Version 3.4, dated 8 April, 1997 — old money, still slaying, periodt. 👑🦋