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authorJunio C Hamano <junkio@cox.net>2006-03-13 04:32:06 (GMT)
committerJunio C Hamano <junkio@cox.net>2006-03-13 04:42:12 (GMT)
commitfc66d213f8b2f13b9ffd643f01de25ddc95e0972 (patch)
tree340b074082effe5b0892cf67db309dd6fab3e1f8
parent2821104db7fabdfac105ae757228b0eac107047c (diff)
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diffcore-delta: tweak hashbase value.
This tweaks the maximum hashvalue we use to hash the string into without making the maximum size of the hashtable can grow from the current limit. With this, the renames detected becomes a bit more precise without incurring additional paging cost. Signed-off-by: Junio C Hamano <junkio@cox.net>
-rw-r--r--diffcore-delta.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/diffcore-delta.c b/diffcore-delta.c
index f8a7518..835d82c 100644
--- a/diffcore-delta.c
+++ b/diffcore-delta.c
@@ -26,12 +26,19 @@
/* Wild guess at the initial hash size */
#define INITIAL_HASH_SIZE 9
-#define HASHBASE 65537 /* next_prime(2^16) */
+
/* We leave more room in smaller hash but do not let it
* grow to have unused hole too much.
*/
#define INITIAL_FREE(sz_log2) ((1<<(sz_log2))*(sz_log2-3)/(sz_log2))
+/* A prime rather carefully chosen between 2^16..2^17, so that
+ * HASHBASE < INITIAL_FREE(17). We want to keep the maximum hashtable
+ * size under the current 2<<17 maximum, which can hold this many
+ * different values before overflowing to hashtable of size 2<<18.
+ */
+#define HASHBASE 107927
+
struct spanhash {
unsigned long hashval;
unsigned long cnt;