Notes

notes/4_24/collatz_mp.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <gmp.h>
+
+int main(int argc, char *argv[]) {
+	int i;
+	mpz_t val;
+	mpz_t op1;
+	mpz_t op2;
+
+	mpz_init(val);
+	mpz_init(op1);
+	mpz_init(op2);
+
+	gmp_sscanf(argv[1], "%Zd", val);
+
+	mpz_set_ui(op2, 1);
+
+	if (mpz_cmp_ui(val, 1)) {
+		for (i = 1; mpz_cmp_ui(val, 1); i++) {
+			mpz_and(op1, val, op2);
+			if (mpz_get_ui(op1)) {
+				//odd
+				mpz_mul_ui(val, val, 3);
+				mpz_add_ui(val, val, 1);
+			} else {
+				// even
+				mpz_tdiv_q_ui(val, val, 2);
+			}
+		}
+		printf("%d\n", i-1);
+	}
+	return 0;
+}