/* --------------------------------------------------------------------
* POP OPERATION
*/
int Ast_pop (Astack stack)
{
AstNode node = NULL;
int datum;
/* 0. CHECK EMPTY */
if (Ast_more(stack)==FALSE)
Asystem_error("Ast_pop","Empty stack","");
/* 1. REMEMBER THE NEXT POINTER */
node = (*stack)->next;
/* 2. REMEMBER THE TASK POINTER */
datum = (*stack)->datum;
/* 3. FREEING THE SPACE OF THE NODE */
free(*stack);
/* 4. CHANGING THE STACK POINTER */
*stack = node;
/* 5. RETURNING THE TASK POINTER */
return datum;
}
/*
*
* Graph search. Test if exists a path from a source node to a target node
*
* Parallelization method: Shared-Memory workers-farm
*
*/
void testPath(int nthreads, int source, int target, tg graph) {
/* SHARED STRUCTURES */
Bool *searched=NULL;
Astack pool;
Bool found = FALSE;
int ind;
/* ENDING CONTROL */
int num_waiting=0;
/* 1. ALLOCATE MEMORY FOR ANCILLARY STRUCTURES */
pool = Ast_init();
searched = OSCR_calloc(tg_nodes(graph), sizeof(Bool));
for (ind=0; ind<tg_nodes(graph); ind++) { searched[ind]=FALSE; }
/* 2. INIT "nodes to explore" POOL WITH THE source ID */
Ast_push(pool, source);
/* 3. START TIMER */
OSCR_timer_start(0);
/* 4. SPAWN WORKERS */
#pragma omp parallel default(none) \
shared(nthreads,num_waiting,graph,searched,pool,target,found)
{
Bool waiting = FALSE;
tg_task next=TG_NULLID;
task_list succs;
int num_succs;
int ind;
#ifdef DEBUG
int numPops=0;
int numNoPops=0;
int thread = omp_get_thread_num();
#endif
/* WORKER WORKS UNTIL:
* ALL WORKERS ARE WAITING (TARGET NOT FOUND)
* OR SOMEONE FINDS THE TARGET
*/
while ( num_waiting != nthreads && !found ) {
/* 1. GET NEXT ELEMENT TO PROCESS (OR WAIT UNTIL MORE ELEMENTS) */
while( next == TG_NULLID && num_waiting != nthreads && !found) {
/* ALL POOL OPERATIONS ARE MONITORIZED */
#pragma omp critical
{
/* 1.1. CHECK THE POOL */
if ( Ast_more(pool) ) {
/* 1.1.1. ELEMENTS IN THE POOL: GET NEXT */
next = Ast_pop(pool);
#ifdef DEBUG
numPops++;
#endif
/* 1.1.2. IF WAITING, CHANGE STATE */
if ( waiting ) {
waiting = FALSE;
num_waiting--;
}
}
else {
/* 1.1.3. EMPTY POOL: IF NOT WAITING, CHANGE STATE */
#ifdef DEBUG
numNoPops++;
#endif
if ( !waiting ) {
waiting = TRUE;
num_waiting++;
}
}
/* OMP END CRITICAL: MONITORIZED OPERATION */
}
} /* END GET next ELEMENT FROM THE POOL */
/* 2. PROCESS next ELEMENT */
if ( next != TG_NULLID ) {
/* 2.1. TARGET FOUND: END ALL */
if (next == target) { found = TRUE; }
/* 2.2. NO SUCCESORS: END */
else if ( tg_succ_num(graph, next) == 0 ) { next = TG_NULLID; }
/* 2.3. GET SUCCESORS LIST AND PUSH IT TO THE POOL */
else {
/* 2.3.1. GET SUCCS LIST */
num_succs = tg_succ_num(graph, next);
succs = tg_succ(graph, next);
/* 2.3.2. PUSH SUCCS TO POOL: MONITORIZED OPERATION */
#pragma omp critical
if ( num_succs > 0 ) {
for(ind=0; ind<num_succs; ind++) {
tg_task vp = succs[ind];
/* PUSH ONLY NON-EXPLORED NODES */
if ( ! searched[ vp ] ) {
searched[ vp ] = TRUE;
Ast_push(pool, vp);
}
}
/* END OMP CRITICAL: MONITORIZED OPERATION */
}
}
/* 2.4. END PROCESSING ELEMENT */
next = TG_NULLID;
}
} /* END PROCESSING */
#ifdef DEBUG
printf("#DEBUG Thread %d ENDING ----> Pops: %d, NoPops: %d\n",thread,numPops,numNoPops);
#endif
/* WORKERS END: PARALLEL REGION */
}
/* 5. STOP TIMER */
OSCR_timer_stop(0);
/* 6. WRITE RESULT */
printf("\nPath(%d,%d) = %d\n\n", source, target, found);
/* 7. END */
}
