*** empty log message ***

1 files changed, 127 insertions, 0 deletions

diff --git a/demos/primes.c b/demos/primes.c
new file mode 100644
index 000000000..3cf478dd8
--- /dev/null
+++ b/demos/primes.c
@@ -0,0 +1,127 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include "gmp.h"
+
+/* Sieve table size */
+#define ST_SIZE 30000
+/* Largest prime to sieve with */
+#define MAX_S_PRIME 1000
+
+main (int argc, char **argv)
+{
+  char *progname = argv[0];
+  mpz_t r0, r1;			/* range */
+  mpz_t cur;
+  unsigned char *st;
+  unsigned long i, ii;
+  unsigned long nprimes = 0;
+  unsigned long last;
+  int flag_print = 1;
+  int flag_count = 0;
+
+  st = malloc (ST_SIZE);
+
+  while (argc != 1)
+    {
+      if (strcmp (argv[1], "-c") == 0)
+	{
+	  flag_count = 1;
+	  argv++;
+	  argc--;
+	}
+      else if (strcmp (argv[1], "-p") == 0)
+	{
+	  flag_print = 2;
+	  argv++;
+	  argc--;
+	}
+      else
+	break;
+    }
+
+  if (flag_count)
+    flag_print--;		/* clear unless an explicit -p  */
+
+  mpz_init (r0);
+  mpz_init (r1);
+  mpz_init (cur);
+
+  if (argc == 2)
+    {
+      mpz_set_ui (r0, 2);
+      mpz_set_str (r1, argv[1], 0);
+    }
+  else if (argc == 3)
+    {
+      mpz_set_str (r0, argv[1], 0);
+      if (argv[2][0] == '+')
+	{
+	  mpz_set_str (r1, argv[2] + 1, 0);
+	  mpz_add (r1, r1, r0);
+	}
+      mpz_set_str (r1, argv[2], 0);
+    }
+  else
+    {
+      fprintf (stderr, "usage: %s [-c] [-g] [from [+]]to\n", progname);
+      exit (1);
+    }
+
+  if (mpz_cmp_ui (r0, 2) < 0)
+    mpz_set_ui (r0, 2);
+
+  if ((mpz_get_ui (r0) & 1) == 0)
+    {
+      if (mpz_cmp_ui (r0, 2) == 0)
+	{
+	  if (flag_print)
+	    puts ("2");
+	  nprimes++;
+	}
+      mpz_add_ui (r0, r0, 1);
+    }
+
+  mpz_set (cur, r0);
+
+  while (mpz_cmp (cur, r1) <= 0)
+    {
+      memset (st, 1, ST_SIZE);
+      for (i = 3; i < MAX_S_PRIME; i += 2)
+	{
+	  unsigned long start;
+	  start = mpz_tdiv_ui (cur, i);
+	  if (start != 0)
+	    start = i - start;
+	  
+	  if (mpz_cmp_ui (cur, i - start) == 0)
+	    start += i;
+	  for (ii = start; ii < ST_SIZE; ii += i)
+	    st[ii] = 0;
+	}
+      last = 0;
+      for (ii = 0; ii < ST_SIZE; ii += 2)
+	{
+	  if (st[ii] != 0)
+	    {
+	      mpz_add_ui (cur, cur, ii - last);
+	      last = ii;
+	      if (mpz_cmp (cur, r1) > 0)
+		goto done;
+	      if (mpz_probab_prime_p (cur, 3))
+		{
+		  nprimes++;
+		  if (flag_print)
+		    {
+		      mpz_out_str (stdout, 10, cur); puts ("");
+		    }
+		}
+	    }
+	}
+      mpz_add_ui (cur, cur, ST_SIZE - last);
+    }
+ done:
+  if (flag_count)
+    printf ("Pi(interval) = %lu\n", nprimes);
+
+  exit (0);
+}