Initial data commit

Task/Miller-Rabin-primality-test/Bc/miller-rabin-primality-test.bc

@@ -0,0 +1,68 @@
+seed = 1   /* seed of the random number generator */
+scale = 0
+
+/* Random number from 0 to 32767. */
+define rand() {
+  /* Cheap formula (from POSIX) for random numbers of low quality. */
+  seed = (seed * 1103515245 + 12345) % 4294967296
+  return ((seed / 65536) % 32768)
+}
+
+/* Random number in range [from, to]. */
+define rangerand(from, to) {
+  auto b, h, i, m, n, r
+
+  m = to - from + 1
+  h = length(m) / 2 + 1  /* want h iterations of rand() % 100 */
+  b = 100 ^ h % m        /* want n >= b */
+  while (1) {
+    n = 0                /* pick n in range [b, 100 ^ h) */
+    for (i = h; i > 0; i--) {
+      r = rand()
+      while (r < 68) { r = rand(); }  /* loop if the modulo bias */
+      n = (n * 100) + (r % 100)       /* append 2 digits to n */
+    }
+    if (n >= b) { break; }  /* break unless the modulo bias */
+  }
+  return (from + (n % m))
+}
+
+
+
+/* n is probably prime? */
+define miller_rabin_test(n, k) {
+  auto d, r, a, x, s
+
+  if (n <= 3) { return (1); }
+  if ((n % 2) == 0) { return (0); }
+
+  /* find s and d so that d * 2^s = n - 1 */
+  d = n - 1
+  s = 0
+  while((d % 2) == 0) {
+     d /= 2
+     s += 1
+  }
+
+  while (k-- > 0) {
+    a = rangerand(2, n - 2)
+    x = (a ^ d) % n
+    if (x != 1) {
+      for (r = 0; r < s; r++) {
+        if (x == (n - 1)) { break; }
+        x = (x * x) % n
+      }
+      if (x != (n - 1)) {
+        return (0)
+      }
+    }
+  }
+  return (1)
+}
+
+for (i = 1; i < 1000; i++) {
+  if (miller_rabin_test(i, 10) == 1) {
+    i
+  }
+}
+quit