Changeset: 5d5b515419e0 for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=5d5b515419e0
Modified Files:
gdk/gdk_hash.h
Branch: Jul2017
Log Message:
Better hash functions for 64 and 128 bit integers.
The main problem with the old version is that it works very badly if
you use a trick to combine multiple 32 bit values in a single 64 or
128 bit value.
diffs (38 lines):
diff --git a/gdk/gdk_hash.h b/gdk/gdk_hash.h
--- a/gdk/gdk_hash.h
+++ b/gdk/gdk_hash.h
@@ -134,10 +134,31 @@ gdk_export BUN HASHlist(Hash *h, BUN i);
((unsigned int) (X) >> 13) ^ \
((unsigned int) (X) >> 21) ^ \
(unsigned int) (X))
-#define mix_lng(X) mix_int((unsigned int) ((ulng) (X) ^ \
- ((ulng) (X) >> 32)))
+#define mix_lng(X) (((ulng) (X) >> 7) ^ \
+ ((ulng) (X) >> 13) ^ \
+ ((ulng) (X) >> 21) ^ \
+ ((ulng) (X) >> 31) ^ \
+ ((ulng) (X) >> 38) ^ \
+ ((ulng) (X) >> 46) ^ \
+ ((ulng) (X) >> 56) ^ \
+ (ulng) (X))
#ifdef HAVE_HGE
-#define mix_hge(X) mix_lng((ulng) ((uhge) (X) ^ ((uhge) (X) >> 64)))
+#define mix_hge(X) (((uhge) (X) >> 7) ^ \
+ ((uhge) (X) >> 13) ^ \
+ ((uhge) (X) >> 21) ^ \
+ ((uhge) (X) >> 31) ^ \
+ ((uhge) (X) >> 38) ^ \
+ ((uhge) (X) >> 46) ^ \
+ ((uhge) (X) >> 56) ^ \
+ ((uhge) (X) >> 65) ^ \
+ ((uhge) (X) >> 70) ^ \
+ ((uhge) (X) >> 78) ^ \
+ ((uhge) (X) >> 85) ^ \
+ ((uhge) (X) >> 90) ^ \
+ ((uhge) (X) >> 98) ^ \
+ ((uhge) (X) >> 107) ^ \
+ ((uhge) (X) >> 116) ^ \
+ (uhge) (X))
#endif
#define hash_loc(H,V) hash_any(H,V)
#define hash_var(H,V) hash_any(H,V)
_______________________________________________
checkin-list mailing list
[email protected]
https://www.monetdb.org/mailman/listinfo/checkin-list
