Correctly round towards zero in random(uint32_t)

2007-08-21 14:47:14 +00:00 · 2007-08-21 14:47:14 +00:00 · ac601df371
commit ac601df371
parent 797896e002
1 changed files with 4 additions and 1 deletions
--- a/eo/src/utils/eoRNG.h
+++ b/eo/src/utils/eoRNG.h
@ -178,7 +178,10 @@ public :
    */
    uint32_t random(uint32_t m)
        {
-            return uint32_t(uniform() * double(m));
+            // Make sure we always round towards zero, in order to get the
+            // half-open interval we want (as documented). The floor function
+            // does exactly this for the (always positive) values occuring here.
+            return uint32_t(floor(uniform() * double(m)));
        }

    /** Biased coin toss