man pvm_newcontext () - Request new context. pvm_setcontext - Change context. pvm_freecontext - Free existing context. pvm_getcontext - Get current context.

NAME

pvm_newcontext - Request new context.

pvm_setcontext - Change context.

pvm_freecontext - Free existing context.

pvm_getcontext - Get current context.

SYNOPSIS

C	int ctx = pvm_newcontext( void )



	int old_ctx = pvm_setcontext( int new_ctx )



	int info = pvm_freecontext( ctx )



	int ctx = pvm_getcontext( void )

Fortran

call pvmfnewcontext( ctx )

call pvmfsetcontext( new_ctx, old_ctx )

call pvmffreecontext( ctx, info )

call pvmfgetcontext( ctx )

PARAMETERS

ctx


Context value.
new_ctx


New context value.
old_ctx


Prior context value.
info


Result code.

DESCRIPTION

The context functions provide a system-wide unique context and the means to manipulate this context.

Contexts provide the ability for communicating tasks to automatically differentiate messages by the context in which they were sent. Thus a message sent in context A by the sender must be received in context A by the recipient. A sender may send in any context. However, a recipient will not accept a message sent in a context that differs from its own.

One such use of contexts is with library routines. Using contexts, library routine inter-communication may be logically seperated from the user's application inter-communication. This will prevent the inadvertent receipt of one another's messages.

Spawned tasks inherit the spawn-time context of their parent. Existing PVM applications work unchanged using the default context.

pvm_newcontext returns a newly allocated context. However, this new context is not yet active.

pvm_setcontext changes the current context from old_ctx to new_ctx.

pvm_freecontext frees ctx so that it may be reused. Contexts are a system resource that will be exhausted if not recycled.

pvm_getcontext returns the current context of the requesting task.

EXAMPLES

/* 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 */ 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);

ERRORS

Only system resource errors will be returned as the context programs themselves do not generate errors.

SEE ALSO