1 files changed, 53 insertions, 0 deletions

diff --git a/03_threads/primes.c b/03_threads/primes.c
new file mode 100644
index 0000000..a5076c6
--- /dev/null
+++ b/03_threads/primes.c
@@ -0,0 +1,53 @@
+#include <stdbool.h>
+#include <pthread.h>
+
+#define NTHREADS 16
+
+bool isprime(int);
+void *pthread_routine(void *);
+
+struct interval { int low; int high; int count; };
+
+int primes_in_range(int low, int high) {
+        pthread_t threads[NTHREADS];
+        struct interval args[NTHREADS];
+
+        if (low < 0 || high < low)
+                return 0;
+
+        int interval_size = (high-low)/NTHREADS + 1;
+        for (int i = 0; i < NTHREADS; i++) {
+                args[i].low = low + i*interval_size;
+                args[i].high = args[i].low + interval_size;
+                pthread_create(&threads[i], NULL, pthread_routine, &args[i]);
+        }
+
+        int result = 0;
+        for (int i = 0; i < NTHREADS; i++) {
+                pthread_join(threads[i], NULL);
+                result += args[i].count;
+        }
+
+        return result;
+}
+
+bool isprime(int n) {
+        if (n < 2)
+                return false;
+
+        for (int i = 2; i*i <= n; i++)
+                if (n % i == 0)
+                        return false;
+        return true;
+}
+
+void *pthread_routine(void *arg) {
+        struct interval *interval = arg;
+
+        interval->count = 0;
+        for (int i = interval->low; i < interval->high; i++)
+                if (isprime(i))
+                        interval->count++;
+
+        return NULL;
+}