ppqueue.c

/*
MIT License

Copyright (c) 2000 Adrien M. Regimbald

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include "pprotos.h"
#define root 0
//parent can't be used by root
#define parent(i) (((i)-1)>>1)
#define left(i)	  (((i)*2)+ 1)
#define right(i)  (((i)*2)+ 2)
#define heap_ele(ppq, i)	*(((ppq)->heap) + i)

//for testing purposes...
int comparefun(void* int_a, void* int_b)
{
	int a = *(int*)int_a, b = *(int*)int_b; 	
	if(a > b)
		return 1;
	else if(a < b)
		return -1;
	else
		return 0;
}

void ppq_test(void)
{
	int i;
	pp_queue* ppq = ppq_create(100, &comparefun);
	printf("\nenqueuing...\n");
	for(i = 0; i < 20; i++)
	{
		int *e = (int*)malloc(sizeof(int));
		*e = rand() % 30;
		printf("%d ", *e);
		ppq_enqueue(ppq, e);
	}
	printf("\ndequeuing...\n");
	for(i = 0; i < 30; i++)
	{
		int *e = ppq_dequeue(ppq);
		if(e)
		{
			printf("%d ", *e);
			free(e);
		}
		else
		{
			printf("X ");
		}
	}
	printf("\nenqueuing...\n");
	for(i = 0; i < 10; i++)
	{
		int *e = (int*)malloc(sizeof(int));
		*e = rand() % 30;
		printf("%d ", *e);
		ppq_enqueue(ppq, e);
	}
	printf("\ndequeuing...\n");
	for(i = 0; i < 15; i++)
	{
		int *e = ppq_dequeue(ppq);
		if(e)
		{
			printf("%d ", *e);
			free(e);
		}
		else
		{
			printf("X ");
		}
	}
	printf("\n");
	ppq_free(ppq);
}

//it will create a queue of
pp_queue* ppq_create(int cap, compare compare_func)
{
	pp_queue* ppq;
	//int 	  ret;
	if((ppq = (pp_queue*)malloc(sizeof(pp_queue))) == NULL)
		error_shutdown("pp_queue malloc", -1);	
	if((ppq->heap = (void**)malloc(sizeof(void*) * cap)) == NULL)
		error_shutdown("pp_queue heap malloc", -1);
	ppq->size = 0;
	ppq->cap = cap;
	ppq->compare_func = compare_func;
	//if((ret = pthread_spin_init(&(ppq->s_lock), PTHREAD_PROCESS_PRIVATE)))
	//	error_shutdown("pp_queue spin lock init", ret);
	return ppq;
}

//enqueues an element to the parallel priority queue
void ppq_enqueue(pp_queue* ppq, void* e)
{
	int i;// ret; 
	void** p;
	//if((ret = pthread_spin_lock(&(ppq->s_lock))))	
	//	error_shutdown("pp_queue enqueue spin lock lock", ret);
	//enqueue element in min queue
	ppq->size++;
	//initial position of node in head
	i = ppq->size - 1;
	while(i != root)
	{
		p = ppq->heap + parent(i);
		if(ppq->compare_func(*p, e) > 0)
		{
			heap_ele(ppq, i) = *p;
		}
		else
		{
			break;	
		}
		i = parent(i);
	}	
	
	heap_ele(ppq, i) = e;
	//if((ret = pthread_spin_unlock(&(ppq->s_lock))))
//		error_shutdown("pp_queue enqueue spin lock unlock", ret);
}

//dequeues and element from the paralle priority queue
void* ppq_dequeue(pp_queue* ppq)
{
	int i, l, r, smallest, last;
	//int ret;
	void *tmp, *min = NULL;
	compare func;

	//if((ret = pthread_spin_lock(&(ppq->s_lock))))	
	//	error_shutdown("pp_queue enqueue spin lock lock", ret);

	if(ppq->size)
	{
		last = (--ppq->size);
		min = heap_ele(ppq, 0);
		//change the last element to be the min element
		heap_ele(ppq, 0) = heap_ele(ppq, last);
		//setup some variables before beginning to heapify
		i = 0;
		func = ppq->compare_func;
		while(1)
		{
			l = left(i);
			r = right(i);
			if(l < last && (func(heap_ele(ppq, l), heap_ele(ppq, i)) < 0))
				smallest = l;	
			else
				smallest = i;
			
			if(r < last && (func(heap_ele(ppq, r), heap_ele(ppq, smallest)) < 0))
				smallest = r;	
			
			if(smallest == i)
				break;

			tmp = heap_ele(ppq, i);
			heap_ele(ppq, i) = heap_ele(ppq, smallest);
			heap_ele(ppq, smallest) = tmp;
			i = smallest;
		}	
	}

	//if((ret = pthread_spin_unlock(&(ppq->s_lock))))
//		error_shutdown("pp_queue enqueue spin lock unlock", ret);

	return min;
}

void ppq_free(pp_queue* ppq)
{
	//int ret;
	//free up memory can only be called by one thread for a specific
	//parallel priority queue else behaviour is undefined
	//if((ret = pthread_spin_destroy(&(ppq->s_lock))))
	//	error_shutdown("pp_queue spin lock destroy", ret);
	free(ppq->heap);
	free(ppq);
}