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authorDaniel Friesel <derf@finalrewind.org>2014-05-05 21:22:12 +0200
committerDaniel Friesel <derf@finalrewind.org>2014-05-05 21:23:55 +0200
commitf0fd0413e2904e0824707d866a044341184bbe13 (patch)
tree50bef4a185e2ff13a55b4b8fd238181abf1badf6
parent68037c4d220302a9f7ab250b3a220a5f64217244 (diff)
gib_list_randomize: use code better suited for short lists (closes #151)
Note that the i == r check was never reached in the original code but may be in the new variant. Since a shuffled list may well have one or two elements retain their absolute position once in a while, this should not be a problem. tests with 2- and 3-element lists show an even distribution amongst all elements.
-rw-r--r--ChangeLog1
-rw-r--r--src/gib_list.c10
2 files changed, 5 insertions, 6 deletions
diff --git a/ChangeLog b/ChangeLog
index 375a80b..0a441c9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -9,6 +9,7 @@ git HEAD
three projects (one of which is feh). There is at least one known bug
in it, and as I do not have the time to take over giblib development,
importing the library seems to be the best solution.
+ * Fix/improve --randomize for short filelists (closes #151)
Sun, 27 Apr 2014 20:28:02 +0200 Daniel Friesel <derf+feh@finalrewind.org>
diff --git a/src/gib_list.c b/src/gib_list.c
index 1c313ba..a05fb4c 100644
--- a/src/gib_list.c
+++ b/src/gib_list.c
@@ -362,12 +362,10 @@ gib_list_randomize(gib_list * list)
srand(getpid() * time(NULL) % ((unsigned int) -1));
for (i = 0; i < len - 1; i++)
{
- r = (int) ((len - i - 1) * ((float) rand()) / (RAND_MAX + 1.0)) + i + 1;
- if (i == r)
- abort();
- t = farray[i];
- farray[i] = farray[r];
- farray[r] = t;
+ r = i + rand() / (RAND_MAX / (len - i) + 1 );
+ t = farray[r];
+ farray[r] = farray[i];
+ farray[i] = t;
}
list = farray[0];
list->prev = NULL;