Created
March 11, 2014 17:02
-
-
Save gyng/f50ef749fb34df45cc70 to your computer and use it in GitHub Desktop.
amazing revolutionary parallel fibonacci algorithm do not steal
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
#include <stdio.h> | |
#include <stdlib.h> | |
#include <unistd.h> | |
#include <sys/wait.h> | |
#include <errno.h> | |
void handle_error(void); | |
int main(int argc, char **argv) | |
{ | |
int n = atoi(argv[1]); | |
int superdaddy = getpid(); | |
int p1[2]; | |
int p2[2]; | |
int *pipes[2] = { p1, p2 }; | |
int savedoutput, result1, result2, result, cpid; | |
int output = STDOUT_FILENO; | |
int i; | |
// Trivial cases | |
if (n <= 2) | |
{ | |
printf("Result: 1\n"); | |
return 0; | |
} | |
fib: | |
if (n <= 1) | |
{ | |
// Base case | |
if (write(output, &n, sizeof(n)) < 0) handle_error(); | |
return 0; | |
} | |
// Pipe to parent, write fib(n) into this | |
savedoutput = output; | |
// Fork twice, once for fib(n-1) and another for fib(n-2) | |
for (i = 0; i < 2; i++) | |
{ | |
n--; | |
if (pipe(pipes[i]) < 0) handle_error(); | |
output = pipes[i][1]; | |
if ((cpid = fork()) == 0) | |
{ | |
// In child process | |
// Close pipe reading ends and perform recursion | |
if (close(pipes[i][0]) < 0) handle_error(); | |
goto fib; | |
} | |
else if (cpid < 0) | |
handle_error(); | |
} | |
// Close pipe outputs | |
if (output == p1[1] && close(p1[1]) < 0) handle_error(); | |
if (output == p2[1] && close(p2[1]) < 0) handle_error(); | |
// fib(n) = fib(n-1) + fib(n-2) | |
if (read(p1[0], &result1, sizeof(result1)) < 0) handle_error(); | |
if (read(p2[0], &result2, sizeof(result2)) < 0) handle_error(); | |
result = result1 + result2; | |
if (getpid() == superdaddy) | |
printf("Result: %d\n", result); | |
else if (write(savedoutput, &result, sizeof(result)) < 0) | |
handle_error(); | |
wait(NULL); | |
wait(NULL); | |
return 0; | |
} | |
void handle_error(void) | |
{ | |
perror(NULL); | |
exit(EXIT_FAILURE); | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment