Change the token prehash function for better convergence

Combining arithmetric (add) and bitwise (xor) mixing seems to give
better result than either.

With the new prehash function, we find a valid hash much quicker.

1 files changed, 2 insertions, 2 deletions

diff --git a/pptok.pl b/pptok.pl
index a0425b7c..a835bf3e 100755
--- a/pptok.pl
+++ b/pptok.pl
@@ -191,8 +191,8 @@ if ($what eq 'c') {
     print OUT  "    while ((c = *p++) != 0) {\n";
     print OUT  "        uint32_t kn1, kn2;\n";
     print OUT  "        c |= 0x20; /* convert to lower case */\n";
-    printf OUT "        kn1 = rot(k1,%2d) - rot(k2,%2d) + c;\n", ${$sv}[0], ${$sv}[1];
-    printf OUT "        kn2 = rot(k2,%2d) - rot(k1,%2d) + c;\n", ${$sv}[2], ${$sv}[3];
+    printf OUT "        kn1 = rot(k1,%2d)^(rot(k2,%2d) + c);\n", ${$sv}[0], ${$sv}[1];
+    printf OUT "        kn2 = rot(k2,%2d)^(rot(k1,%2d) + c);\n", ${$sv}[2], ${$sv}[3];
     print OUT  "        k1 = kn1; k2 = kn2;\n";
     print OUT  "    }\n";
     print OUT  "\n";