Re: [pacman-dev] [PATCH] Improved alpm_list_mmerge() performance

On Wed, Aug 24, 2011 at 9:29 AM, Diogo Sousa wrote:

Improved alpm_list_mmerge() performance by removing an extra final linear search of the tail node. This was actually suggested by a TODO comment.

Signed-off-by: Diogo Sousa ---  lib/libalpm/alpm_list.c |   18 ++++++++++--------  1 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/lib/libalpm/alpm_list.c b/lib/libalpm/alpm_list.c index 83b9824..d50dce1 100644 --- a/lib/libalpm/alpm_list.c +++ b/lib/libalpm/alpm_list.c @@ -206,13 +206,17 @@ alpm_list_t SYMEXPORT *alpm_list_join(alpm_list_t *first, alpm_list_t *second)  */  alpm_list_t SYMEXPORT *alpm_list_mmerge(alpm_list_t *left, alpm_list_t *right, alpm_list_fn_cmp fn)  { -       alpm_list_t *newlist, *lp; +       alpm_list_t *newlist, *lp, *tail_ptr, *left_tail_ptr, *right_tail_ptr;

       if(left == NULL)                return right;        if(right == NULL)                return left;

+        /* Save tail node pointers for future use */ +       left_tail_ptr=left->prev; +       right_tail_ptr=right->prev; <space>=<space> please, here and everywhere else.

+        if(fn(left->data, right->data) <= 0) {                newlist = left;                left = left->next; @@ -242,19 +246,17 @@ alpm_list_t SYMEXPORT *alpm_list_mmerge(alpm_list_t *left, alpm_list_t *right, a        if(left != NULL) {                lp->next = left;                left->prev = lp; +               tail_ptr=left_tail_ptr;        }        else if(right != NULL) {                lp->next = right;                right->prev = lp; +               tail_ptr=right_tail_ptr;        } +       else +               tail_ptr=lp; We never omit {} in conditionals. See HACKING.

-       /* Find our tail pointer -        * TODO maintain this in the algorithm itself */ -       lp = newlist; -       while(lp && lp->next) { -               lp = lp->next; -       } -       newlist->prev = lp; +       newlist->prev = tail_ptr;

Otherwise this looks good, thanks! I'll apply after a resubmit with noted touchups.

       return newlist;  } -- 1.7.6