Update of /cvsroot/monetdb/MonetDB4/src/modules/plain
In directory sc8-pr-cvs16.sourceforge.net:/tmp/cvs-serv11545/src/modules/plain
Modified Files:
Tag: MonetDB_4-20
xtables.mx
Log Message:
performance fix in derive: we now do an sample now to make a more educated guess
Index: xtables.mx
===================================================================
RCS file: /cvsroot/monetdb/MonetDB4/src/modules/plain/xtables.mx,v
retrieving revision 1.4
retrieving revision 1.4.2.1
diff -u -d -r1.4 -r1.4.2.1
--- xtables.mx 6 Sep 2007 13:25:22 -0000 1.4
+++ xtables.mx 22 Oct 2007 19:55:13 -0000 1.4.2.1
@@ -700,6 +700,30 @@
break;
}
[EMAIL PROTECTED]
+#define SAMPLE_SIZE 1024
+hash_t
+derive_mask( BAT *ct_histo, BAT *b)
+{
+ int n = bits(BATcount(ct_histo)), *N = &n;
+
+ if (BATcount(b) > (SAMPLE_SIZE<<3)) {
+ BAT *s = BATsample(b, SAMPLE_SIZE);
+ BAT *u = BATkunique(BATmirror(s));
+ size_t uc = BATcount(u);
+
+ BBPunfix(s->batCacheid);
+ BBPunfix(u->batCacheid);
+ if (uc > 0) {
+ size_t ratio = (((dbl)BATcount(b)/SAMPLE_SIZE) * uc);
+ if (ratio > 0)
+ return (1<<bits(*N * ratio)) - 1;
+ }
+ }
+ /* default to */
+ return (1<<*N) - 1;
+}
+
@= derive
static BAT *
[EMAIL PROTECTED]@[EMAIL PROTECTED](BAT* ct_map, BAT *ct_histo, BAT *b, BAT
*bn, map_T *m)
@@ -710,9 +734,8 @@
BUN p, q, r, cp = BUNfirst(ct_map) - yy;
mapentry_t entry, *e;
BAT *map;
- int n = bits(BATcount(ct_histo)), *N = &n;
[EMAIL PROTECTED]
- declare_mask_CUSTOM
+ hash_t mask = derive_mask(ct_histo, b);
int custom_rng = BATcount(ct_histo); /* expected number of groups */
hash_t custom_MASK = mask;
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