Category : Files from Magazines
Archive : DDJ0892.ZIP
Filename : PARA_C.ASC
Output of file : PARA_C.ASC contained in archive : DDJ0892.ZIP
by Barr E. Bauer
[LISTING ONE]
/* Loop parallelism sum reduction critical block within loop nest
* B. E. Bauer 1992 -- compiled using the following on the IRIS:
* parallel: cc -O2 -o example1p -mp example1.c
* serial: cc -O2 -o example1 example1.c */
#include
#define MAX 1536
double a[MAX][MAX], b[MAX][MAX];
main()
{
int i, j, k, k1;
double sum=0.0, temp;
/* shared arrays filled; values not important, just order */
for (i=0; i
b[i][j] = (double)j;
}
}
k1 = 256; /* inner loop delay factor */
/* start of parallel region */
#pragma parallel shared(a,b,sum) local(i,j,k,temp) byvalue(k1)
{
/* pfor block */
#pragma pfor iterate(i=0; MAX; 1)
for (i=0; i
for (k=0; k
#pragma critical
{
sum += temp; /* summation in inner loop */
}
}
}
}
printf("\nDone! sum = %24.15f\n", sum);
}
[LISTING TWO]
/* Loop parallelism sum reduction critical block moved into local code
* B. E. Bauer 1992 -- compiled using the following on the IRIS:
* parallel: cc -O2 -o example2p -mp example2.c
* serial: cc -O2 -o example2 example2.c */
#include
#define MAX 1536
double a[MAX][MAX], b[MAX][MAX];
main()
{
int i, j, k, k1;
double sum=0.0, temp, st; /* st = local code subtotal */
/* shared arrays filled; values not important, just order */
for (i=0; i
b[i][j] = (double)j;
}
}
k1 = 256; /* inner loop delay factor */
/* start of parallel region */
#pragma parallel shared(a,b,sum) local(i,j,k,temp,st) byvalue(k1)
{
st = 0.0; /* st initialized in each thread */
/* pfor block */
#pragma pfor iterate(i=0; MAX; 1)
for (i=0; i
for (k=0; k
st += temp;
}
}
/* local code grand summation */
#pragma critical
{
sum += st;
}
}
printf("\nDone! sum = %24.15f\n", sum);
}
[LISTING THREE]
/* Block parallelism, producer-consumer problem
* B. E. Bauer 1992 -- Taken from "Practical Parallel Programming" pp 214-225
* (C) 1992 Academic Press, Inc. All Rights Reserved. Used with permission. */
#include
#define MAXCONSUMERS 3
#define MAXPRODUCTS 10000
#define STOP_TOKEN -1
#define NULL_ITEM (node_t *)NULL
/* the product is defined here */
struct node
{
int productid;
struct node *next;
};
typedef struct node node_t; /* the typedef is convenient */
node_t *root = NULL_ITEM; /* linked list root */
int max_depth = 0;
/* ----- create a new "product" -------------------------------- */
node_t *make_product(node_t *item, int prodid)
{
item = (node_t *)malloc(sizeof(node_t));
if (item != NULL_ITEM) {
item->productid = prodid;
item->next = NULL_ITEM;
}
else
printf("problems with production, boss...\n");
return (item);
}
/* ----- add a "product" to the end of the list ---------------- */
node_t *ship_product(node_t *new)
{
int cur_depth = 0;
node_t *list = root;
if (root == NULL_ITEM)
root = new;
else
{
while (list->next != NULL_ITEM)
{
list = list->next;
cur_depth++;
}
cur_depth++;
list->next = new;
}
if (cur_depth > max_depth)
max_depth = cur_depth;
}
/* ----- pop the product off the beginning of the list --------- */
node_t *receive_product()
{
node_t *item = root;
if (root != NULL_ITEM)
root = root->next;
return(item);
}
/* ----- consume the product by freeing its memory ------------- */
void consume_product(node_t *item)
{
if (item != NULL_ITEM)
free (item);
}
/* ----- the producer ------------------------------------------ */
void producer(int cnt)
{
node_t *temp;
int i;
/* make "products" cnt times (limits simulation) */
for (i=0; i<=cnt; i++)
{
if ((temp = make_product(temp,i)) == NULL_ITEM)
break;
#pragma critical
{
ship_product(temp);
}
}
/* load on stop tokens */
for (i=0; i
if ((temp = make_product(temp, STOP_TOKEN)) == NULL_ITEM)
break;
#pragma critical
{
ship_product(temp);
}
}
printf("producer calls it quits\n");
}
/* ----- the consumer (created 3 times) ------------------------ */
long consumer(int myid)
{
/* local variables */
int consuming = 1, j;
long consumed = 0; /* count of "products" */
node_t *item;
double temp;
printf("consumer %d starts the shopping day\n", myid);
while (consuming) /* loop until stop token seen */
{
for (j=0; j<32000; j++)
temp *= (double)j;
#pragma critical
{
item = receive_product();
}
if (item != NULL_ITEM)
{
if (item->productid != STOP_TOKEN)
{
if (item->productid)
++consumed;
printf("consumer %d consuming product %d\n",
myid, item->productid);
}
else
{
consuming = 0;
printf("consumer %d ran out of products\n", myid);
}
consume_product(item);
}
}
printf("consumer %d consumed %d products\n", myid, consumed);
return(consumed);
}
main()
{
long total, sum[MAXCONSUMERS];
int i;
printf("business starts with %d products\n",MAXPRODUCTS);
#pragma parallel shared(sum)
{
#pragma independent
{
producer(MAXPRODUCTS); /* start producer */
}
#pragma independent
{
sum[0] = consumer(1); /* start consumer 1 */
}
#pragma independent
{
sum[1] = consumer(2); /* start consumer 2 */
}
#pragma independent
{
sum[2] = consumer(3); /* start consumer 3 */
}
}
for (i=0, total = 0L; i
printf("business over, %d products exchanged\n", total);
printf("maximum products in list = %d\n", max_depth-MAXCONSUMERS);
}
Example 1:
(a)
for (sum=i=0; i
(b)
for (i=1; i
Example 2:
(a)
Code Block becomes
#pragma parallel
#pragma shared (arrayvar1, arrayvar2..., grandtotal)
#pragma local (index1, index2, subtotal1,...)
#pragma byvalue(shared_constant1,...)
{
Code Block
}
or, the equivalent
#pragma parallel shared(list) local(list) byvalue(list)
{
Code Block
}
(b)
/* strictly local code */
#pragma parallel
#pragma local(i, j)
{
for (i=sum=0; i<1000; i++)
sum += i;
printf("sum = %d\n", sum);
}
Example 3:
for (i=0; i
becomes
#pragma parallel shared(a,b) local(i) byvalue(max,const)
{
#pragma pfor iterate(i=0; max; 1)
for (i=0; i
}
Example 4:
code block 1
code block 2
becomes
#pragma parallel shared(list) local(list) byvalue(list)
{
#pragma independent
{
code block 1
}
#pragma independent
{
code block 2
}
}
Example 5:
(a)
sum = 0.0;
#pragma parallel shared (sum, a) local(i) byvalue(max)
{
#pragma pfor iterate (i=0; max; 1)
for (i=0; i
}
(b)
sum = 0.0;
#pragma parallel shared (sum, a) local(i) byvalue(max)
{
#pragma pfor iterate (i=0; max; 1)
for (i=0; i
{
sum += a[i];
}
}
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