From: Nicholas Nethercote <njn@valgrind.org>
Date: Wed, 28 Sep 2005 14:49:40 +0000 (+0000)
Subject: Make primes.c a bazillion times faster.
X-Git-Tag: svn/VALGRIND_3_1_0~418
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c35f8e62131b475ee0eaea467f1963489decf19d;p=thirdparty%2Fvalgrind.git

Make primes.c a bazillion times faster.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@4810
---

diff --git a/auxprogs/primes.c b/auxprogs/primes.c
index 2ad817227f..bf2fb82d9b 100644
--- a/auxprogs/primes.c
+++ b/auxprogs/primes.c
@@ -1,10 +1,12 @@
 
 #include <stdio.h>
+#include <math.h>
 
 int isprime ( int n )
 {
    int m;
-   for (m = 2; m < n; m++)
+   int sqrt_n = sqrt(n);
+   for (m = 2; m <= sqrt_n+1; m++)  // +1 in case of obscure rounding error
       if ((n % m) == 0) return 0;
    return 1;
 }