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cs: improve hash-code mixing

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This commit is contained in:
Matthew Flatt 2019-04-03 17:18:37 +02:00
parent 9faa315a7e
commit d8125082a2
1 changed files with 4 additions and 3 deletions
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7
racket/src/cs/rumble/hash-code.ss
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@ -81,7 +81,7 @@
(let* ([+/fx (let* ([+/fx
(lambda (hc k) (lambda (hc k)
(#3%fx+ hc k))] (#3%fx+ hc k))]
[sll/fs [sll/fx
(lambda (hc i) (lambda (hc i)
(#3%fxsll hc i))] (#3%fxsll hc i))]
[->fx [->fx
@ -91,10 +91,11 @@
(modulo v (greatest-fixnum))))] (modulo v (greatest-fixnum))))]
[mix1 [mix1
(lambda (hc) (lambda (hc)
(+/fx hc (sll/fs hc 3)))] (let ([hc2 (+/fx hc (sll/fx hc 10))])
(fxlogxor hc2 (fxsrl hc2 6))))]
[mix2 [mix2
(lambda (hc) (lambda (hc)
(+/fx hc (sll/fs hc 5)))]) (mix1 hc))])
(cond (cond
[(fx> burn MAX-HASH-BURN) (values hc burn)] [(fx> burn MAX-HASH-BURN) (values hc burn)]
[(boolean? x) (values (+/fx hc (if x #x0ace0120 #x0cafe121)) burn)] [(boolean? x) (values (+/fx hc (if x #x0ace0120 #x0cafe121)) burn)]