mirror/mpv
0
0
Fork 0
mirror of https://github.com/mpv-player/mpv.git synced 2024-09-20 03:52:22 +02:00
Code

playlist: improve shuffle algorithm

Browse Source 
The old algorithm produced results which were not uniformly distributed,
i.e. some particular shuffles were preferred over others.

The new algorithm is an implementation of the Fisher-Yates shuffle which
is guaranteed to shuffle uniformly given a sufficiently uniform rand()
and ignoring potential floating-point errors.

Signed-off-by: wm4 <wm4@nowhere>
This commit is contained in:
Niklas Haas 2016-03-20 18:17:34 +01:00 committed by wm4
parent 3353923f29
commit b9c48ca8f3
1 changed files with 3 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
common/playlist.c
View File

@ -169,11 +169,9 @@ void playlist_shuffle(struct playlist *pl)
arr[n] = pl->first;
playlist_unlink(pl, pl->first);
}
for (int n = 0; n < count; n++) {
int other = (int)((double)(count) * rand() / (RAND_MAX + 1.0));
struct playlist_entry *tmp = arr[n];
arr[n] = arr[other];
arr[other] = tmp;
for (int n = 0; n < count - 1; n++) {
int j = (int)((double)(count - n) * rand() / (RAND_MAX + 1.0));
MPSWAP(struct playlist_entry *, arr[n], arr[n + j]);
}
for (int n = 0; n < count; n++)
playlist_add(pl, arr[n]);