Run 8 solving threads in parallel

main.c

@@ -21,6 +21,7 @@
 #include "sud.h"
 
 #include <fcntl.h>
+#include <pthread.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -31,6 +32,29 @@
 #define OFNAME "results"
 #define FSIZE (NPUZZ * NCELLS)
 
+#define NTHREADS 8U
+#define PUZZPT (NPUZZ / NTHREADS)
+#define CELLPT (PUZZPT * NCELLS)
+
+static char *ibuf;
+static char *obuf;
+
+void *threadproc(void *arg)
+{
+	unsigned start = CELLPT * (uintptr_t)arg;
+	const char *libuf = ibuf + start;
+	char *lobuf = obuf + start;
+
+	struct sudoku sud;
+	for (unsigned o = 0; o < CELLPT; o += NCELLS) {
+		load(&sud, libuf + o);
+		solve(&sud);
+		save(&sud, lobuf + o);
+	}
+
+	return NULL;
+}
+
 int main(void)
 {
 	int fd;
@@ -40,7 +64,7 @@ int main(void)
 		fputs("Failed to open puzzles file\n", stderr);
 		return EXIT_FAILURE;
 	}
-	char *ibuf = mmap(NULL, FSIZE, PROT_READ, MAP_PRIVATE, fd, 0);
+	ibuf = mmap(NULL, FSIZE, PROT_READ, MAP_PRIVATE, fd, 0);
 	if (ibuf == MAP_FAILED) {
 		fputs("Failed to mmap() puzzles file\n", stderr);
 		return EXIT_FAILURE;
@@ -52,18 +76,22 @@ int main(void)
 		fputs("Failed to open results file\n", stderr);
 		return EXIT_FAILURE;
 	}
-	char *obuf = mmap(NULL, FSIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	obuf = mmap(NULL, FSIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
 	if (obuf == MAP_FAILED) {
 		fputs("Failed to mmap() results file\n", stderr);
 		return EXIT_FAILURE;
 	}
 	close(fd);
 
-	struct sudoku sud;
-	for (unsigned o = 0; o < FSIZE; o += NCELLS) {
-		load(&sud, ibuf + o);
-		solve(&sud);
-		save(&sud, obuf + o);
+	pthread_t pool[NTHREADS];
+	uintptr_t i;
+	for (i = 0; i < NTHREADS; ++i) {
+		if (pthread_create(&pool[i], NULL, threadproc, (void *)i) != 0)
+			fprintf(stderr, "Failed to create thread #%lu\n", i);
+	}
+	for (i = 0; i < NTHREADS; ++i) {
+		if (pthread_join(pool[i], NULL) != 0)
+			fprintf(stderr, "Failed to join thread #%lu\n", i);
 	}
 
 	munmap(ibuf, FSIZE);