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Issue #249 - Improve hash table performance

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Hardcode bound such that it is not a bignum (reducing bignum allocations).

Replace symbol hash with a more efficient algorithm, since symbols are uniquely identified by memory location as well as name.
This commit is contained in:
Justin Ethier 2018-04-30 13:59:22 -04:00
parent 03c254de14
commit 20379a264c
1 changed files with 13 additions and 5 deletions
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18
srfi/69.sld
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@ -44,7 +44,9 @@
;(scheme cyclone util)
)
(begin
(define *default-bound* (- (expt 2 29) 3))
;; Increased to (2^30) - 1, hardcode to ensure fixnum
(define *default-bound* 1073741823) ;;(- (expt 2 29) 3))
(define (%string-hash s ch-conv bound)
(let ((hash 31)
@ -63,15 +65,21 @@
(let ((bound (if (null? maybe-bound) *default-bound* (car maybe-bound))))
(%string-hash s char-downcase bound)))
(define (symbol-hash s . maybe-bound)
(let ((bound (if (null? maybe-bound) *default-bound* (car maybe-bound))))
(%string-hash (symbol->string s) (lambda (x) x) bound)))
;; Symbols are unique by memory location, so replace old string comparison
(define-c symbol-hash
"(void *data, int argc, closure _, object k, object sym)"
" return_closcall1(data, k, obj_int2obj(((long)sym) & 0x7FFFFFFF)); "
"(void *data, object ptr, object sym)"
" return obj_int2obj(((long)sym) & 0x7FFFFFFF); ")
(define (hash obj . maybe-bound)
(let ((bound (if (null? maybe-bound) *default-bound* (car maybe-bound))))
(cond ((integer? obj) (modulo obj bound))
((string? obj) (string-hash obj bound))
((symbol? obj) (symbol-hash obj bound))
((symbol? obj)
;(symbol-hash obj bound)
(modulo (symbol-hash obj) bound)
)
((real? obj) (modulo (+ (numerator obj) (denominator obj)) bound))
((number? obj)
(modulo (+ (hash (real-part obj)) (* 3 (hash (imag-part obj))))