Decided to drop the dynamically sized hash table for now. This was

due to timing tests showing that the per-byte modulus calculation
slowed down regular sized files.  Kept the other improvements
because they lessened our memory use and actually sped up the code.

diff --git a/match.c b/match.c
index 19b17c5c1f0e78fb9573f63b3d07fc084baa9e23..9ee578850f3bccaed52197f178c443be023d4201 100644 (file)
--- a/match.c
+++ b/match.c
@@ -37,30 +37,24 @@ static int total_matches;
 
 extern struct stats stats;
 
-static uint32 tablesize;
+#define TABLESIZE (1<<16)
+
 static int32 *hash_table;
 
-#define SUM2HASH(sum) ((sum)%tablesize)
+#define SUM2HASH2(s1,s2) (((s1) + (s2)) & 0xFFFF)
+#define SUM2HASH(sum) SUM2HASH2((sum)&0xFFFF,(sum)>>16)
 
 static void build_hash_table(struct sum_struct *s)
 {
        int32 i;
-       uint32 prior_size = tablesize;
-
-       /* Dynamically calculate the hash table size so that the hash load
-        * for big files is about 80%.  This number must be odd or s2 will
-        * not be able to span the entire set. */
-       tablesize = (uint32)(s->count/8) * 10 + 11;
-       if (tablesize < 65537)
-               tablesize = 65537; /* a prime number */
-       if (tablesize != prior_size) {
-               free(hash_table);
-               hash_table = new_array(int32, tablesize);
+
+       if (!hash_table) {
+               hash_table = new_array(int32, TABLESIZE);
                if (!hash_table)
                        out_of_memory("build_hash_table");
        }
 
-       memset(hash_table, 0xFF, tablesize * sizeof hash_table[0]);
+       memset(hash_table, 0xFF, TABLESIZE * sizeof hash_table[0]);
 
        for (i = 0; i < s->count; i++) {
                uint32 t = SUM2HASH(s->sums[i].sum1);
@@ -163,13 +157,16 @@ static void hash_search(int f,struct sum_struct *s,
                int done_csum2 = 0;
                int32 i;
 
-               if (verbose > 4)
-                       rprintf(FINFO,"offset=%.0f sum=%08x\n",(double)offset,sum);
+               if (verbose > 4) {
+                       rprintf(FINFO, "offset=%.0f sum=%04x%04x\n",
+                               (double)offset, s1 & 0xFFFF, s2 & 0xFFFF);
+               }
 
-               i = hash_table[SUM2HASH(sum)];
+               i = hash_table[SUM2HASH2(s1,s2)];
                if (i < 0)
                        goto null_hash;
 
+               sum = (s1 & 0xffff) | (s2 << 16);
                hash_hits++;
                do {
                        int32 l;
@@ -272,7 +269,6 @@ static void hash_search(int f,struct sum_struct *s,
                        s2 += s1;
                } else
                        --k;
-               sum = (s1 & 0xffff) | (s2 << 16);
 
                /* By matching early we avoid re-reading the
                   data 3 times in the case where a token