On 04/09/2014 06:54 AM, Norihiro Tanaka wrote:
memchr() of glibc is faster than seeking by delta1 on some platforms.
So, when there is no chance to match for a while, use it on them.
Speed-up about 3x in best case, 10% in normal case by this patch.
It's still available only for x86 and x86-64 platform.
Thanks, I have some questions about this one.
What benchmark did you use to time this?
THe patch refers to a variable called 'trans' that is not in the current
savannah git master. Is there some other patch that establishes this
variable, a patch that is a prerequisite for this one? If trans is a
cached copy of kwset->trans, isn't that guaranteed to be NULL here?
What is delta1? It's mentioned in a comment but not in the code.
It'd be simpler to use memchr on all platforms; is there a major
performance downside to that? For example, what about the attached
patch instead? It also simplifies things a bit to avoid a label and its
associated gotos, under the assumption that trans is NULL here.
diff --git a/src/kwset.c b/src/kwset.c
index d5db12f..9163482 100644
--- a/src/kwset.c
+++ b/src/kwset.c
@@ -494,29 +494,32 @@ bmexec (kwset_t kwset, char const *text, size_t size)
/* Significance of 12: 1 (initial offset) + 10 (skip loop) + 1 (md2). */
if (size > 12 * len)
/* 11 is not a bug, the initial offset happens only once. */
- for (ep = text + size - 11 * len;;)
+ for (ep = text + size - 11 * len; tp <= ep; )
{
- while (tp <= ep)
+ d = d1[U(tp[-1])], tp += d;
+ d = d1[U(tp[-1])], tp += d;
+ if (d != 0)
{
d = d1[U(tp[-1])], tp += d;
d = d1[U(tp[-1])], tp += d;
- if (d == 0)
- goto found;
- d = d1[U(tp[-1])], tp += d;
- d = d1[U(tp[-1])], tp += d;
- d = d1[U(tp[-1])], tp += d;
- if (d == 0)
- goto found;
- d = d1[U(tp[-1])], tp += d;
- d = d1[U(tp[-1])], tp += d;
- d = d1[U(tp[-1])], tp += d;
- if (d == 0)
- goto found;
- d = d1[U(tp[-1])], tp += d;
d = d1[U(tp[-1])], tp += d;
+ if (d != 0)
+ {
+ d = d1[U(tp[-1])], tp += d;
+ d = d1[U(tp[-1])], tp += d;
+ d = d1[U(tp[-1])], tp += d;
+ if (d != 0)
+ {
+ /* It's typically faster to use memchr when there is
+ no chance to match for a while. */
+ tp = memchr (tp - 1, gc1, text + size - (tp - 1));
+ if (! tp)
+ return -1;
+ tp++;
+ }
+ }
}
- break;
- found:
+
d = len;
while (true)
{
