From 5255fd1f36eece1cbf4000ffc3120dbcb9bf5038 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Tue, 18 Sep 2007 12:38:07 -0700 Subject: 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. --- perllib/phash.ph | 4 ++-- pptok.pl | 4 ++-- tokhash.pl | 4 ++-- 3 files changed, 6 insertions(+), 6 deletions(-) diff --git a/perllib/phash.ph b/perllib/phash.ph index 60334272..3bb3a05b 100644 --- a/perllib/phash.ph +++ b/perllib/phash.ph @@ -42,8 +42,8 @@ sub prehash($$$) { foreach $c (unpack("C*", $key)) { $ko1 = $k1; $ko2 = $k2; - $k1 = int32(rot($ko1,$s0)-rot($ko2, $s1)+$c); - $k2 = int32(rot($ko2,$s2)-rot($ko1, $s3)+$c); + $k1 = int32(rot($ko1,$s0)^int32(rot($ko2, $s1)+$c)); + $k2 = int32(rot($ko2,$s2)^int32(rot($ko1, $s3)+$c)); } # Create a bipartite graph... 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"; diff --git a/tokhash.pl b/tokhash.pl index 5f1a9f4c..9d5888be 100755 --- a/tokhash.pl +++ b/tokhash.pl @@ -187,8 +187,8 @@ print " const char *p = token;\n"; print "\n"; print " while ((c = *p++) != 0) {\n"; -printf " uint32_t kn1 = rot(k1,%2d) - rot(k2,%2d) + c;\n", ${$sv}[0], ${$sv}[1]; -printf " uint32_t kn2 = rot(k2,%2d) - rot(k1,%2d) + c;\n", ${$sv}[2], ${$sv}[3]; +printf " uint32_t kn1 = rot(k1,%2d)^(rot(k2,%2d) + c);\n", ${$sv}[0], ${$sv}[1]; +printf " uint32_t kn2 = rot(k2,%2d)^(rot(k1,%2d) + c);\n", ${$sv}[2], ${$sv}[3]; print " k1 = kn1; k2 = kn2;\n"; print " }\n"; print "\n"; -- cgit v1.2.1