Raymond Toy pushed to branch master at cmucl / cmucl

Commits: bb1bc462 by Raymond Toy at 2024-04-07T22:53:45+00:00 Fix #300: Reduce code duplication in random

- - - - - 94a2c674 by Raymond Toy at 2024-04-07T22:53:51+00:00 Merge branch 'issue-300-reduce-code-dup-in-random' into 'master'

Fix #300: Reduce code duplication in random

Closes #300

See merge request cmucl/cmucl!206 - - - - -

2 changed files:

- src/bootfiles/21e/boot-2023-08.lisp - src/code/rand-xoroshiro.lisp

Changes:

===================================== src/bootfiles/21e/boot-2023-08.lisp ===================================== @@ -2,3 +2,46 @@ ;; *SOFTWARE-VERSION* from the LISP package to the SYSTEM package. (ext:without-package-locks (unintern 'lisp::*software-version* "LISP")) + +#+(or random-mt19937 random-xoroshiro) +(in-package "C") +#+(or random-mt19937 random-xoroshiro) +(deftransform random ((num &optional state) + ((integer 1 #.(expt 2 32)) &optional *)) + _N"use inline (unsigned-byte 32) operations" + (let* ((num-type (continuation-type num)) + (num-high (cond ((numeric-type-p num-type) + (numeric-type-high num-type)) + ((union-type-p num-type) + ;; Find the maximum of the union type. We + ;; know this works because if we're in this + ;; routine, NUM must be a subtype of + ;; (INTEGER 1 2^32), so each member of the + ;; union must be a subtype too. + (reduce #'max (union-type-types num-type) + :key #'numeric-type-high)) + (t + (give-up))))) + ;; Rather than doing (rem (random-chunk) num-high), we do, + ;; essentially, (rem (* num-high (random-chunk)) #x100000000). I + ;; (rtoy) believe this approach doesn't have the bias issue with + ;; doing rem. This method works by treating (random-chunk) as if + ;; it were a 32-bit fraction between 0 and 1, exclusive. Multiply + ;; this by num-high to get a random number between 0 and num-high, + ;; This should have no bias. + (cond ((constant-continuation-p num) + (if (= num-high (expt 2 32)) + '(random-chunk (or state *random-state*)) + '(values (bignum::%multiply + (random-chunk (or state *random-state*)) + num)))) + ((< num-high (expt 2 32)) + '(values (bignum::%multiply (random-chunk (or state *random-state*)) + num))) + ((= num-high (expt 2 32)) + '(if (= num (expt 2 32)) + (random-chunk (or state *random-state*)) + (values (bignum::%multiply (random-chunk (or state *random-state*)) + num)))) + (t + (error (intl:gettext "Shouldn't happen"))))))

===================================== src/code/rand-xoroshiro.lisp ===================================== @@ -490,11 +490,8 @@ (declare (inline %random-single-float %random-double-float)) (cond ((typep arg '(integer 1 #x100000000)) - ;; Do the same thing as the deftransform would do. - (if (= arg (expt 2 32)) - (random-chunk state) - (values (bignum::%multiply (random-chunk state) - arg)))) + ;; Let the compiler deftransform take care of this case. + (random arg state)) ((and (typep arg 'single-float) (> arg 0.0F0)) (%random-single-float arg state)) ((and (typep arg 'double-float) (> arg 0.0D0))

View it on GitLab: https://gitlab.common-lisp.net/cmucl/cmucl/-/compare/7bec290fda1c29972afe323...