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[Sbcl-commits] CVS: sbcl/src/code random.lisp, 1.6, 1.7 target-random.lisp, 1.15, 1.16
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From: William H. N. <wn...@us...> - 2007-03-28 14:33:53
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Update of /cvsroot/sbcl/sbcl/src/code In directory sc8-pr-cvs8.sourceforge.net:/tmp/cvs-serv4483/src/code Modified Files: random.lisp target-random.lisp Log Message: 1.0.4.7: Argh! My shiny new RANDOM-of-INTEGER in 1.0.4.6 was badly broken for 64-bit CPUs. Replace RANDOM-CHUNK with %RANDOM-WORD (mostly) or %RANDOM32 (for code which implicitly knows which foo-FLOAT bit subsequences are <=32 bits). Index: random.lisp =================================================================== RCS file: /cvsroot/sbcl/sbcl/src/code/random.lisp,v retrieving revision 1.6 retrieving revision 1.7 diff -u -d -r1.6 -r1.7 --- random.lisp 27 Mar 2007 16:20:43 -0000 1.6 +++ random.lisp 28 Mar 2007 14:32:12 -0000 1.7 @@ -9,12 +9,6 @@ (in-package "SB!KERNEL") -;;; the size of the chunks returned from the fundamental random number -;;; generator -(def!constant n-random-chunk-bits 32) -(def!constant most-positive-random-chunk - (1- (ash 1 n-random-chunk-bits))) - ;;; our implementation of the RANDOM-STATE type specified by ANSI CL (sb!xc:defstruct (random-state (:constructor %make-random-state) ;; Shallow copy would be wrong: we must Index: target-random.lisp =================================================================== RCS file: /cvsroot/sbcl/sbcl/src/code/target-random.lisp,v retrieving revision 1.15 retrieving revision 1.16 diff -u -d -r1.15 -r1.16 --- target-random.lisp 27 Mar 2007 16:20:46 -0000 1.15 +++ target-random.lisp 28 Mar 2007 14:32:12 -0000 1.16 @@ -102,7 +102,8 @@ ;;; This function generates a 32bit integer between 0 and #xffffffff ;;; inclusive. -#!-sb-fluid (declaim (inline random-chunk)) +(defconstant n-random-mt19937-bits 32) +(declaim (inline %random32)) ;;; portable implementation (defconstant mt19937-n 624) (defconstant mt19937-m 397) @@ -138,7 +139,7 @@ (ash y -1) (aref state (logand y 1))))) (values)) #!-x86 -(defun random-chunk (state) +(defun %random32 (state) (declare (type random-state state)) (let* ((state (random-state-state state)) (k (aref state 2))) @@ -161,9 +162,29 @@ ;;; My inclination is to get rid of the nonportable implementation ;;; unless the performance difference is just enormous. #!+x86 -(defun random-chunk (state) +(defun %random32 (state) (declare (type random-state state)) (sb!vm::random-mt19937 (random-state-state state))) + +(declaim (inline %random-word)) +(defun %random-word (state) + ;; KLUDGE: This #.(ECASE ...) is not the most flexible and elegant + ;; construct one could imagine. It is intended as a quick fix to stand + ;; in for The Right Thing which can't be coded so quickly. + ;; + ;; The Right Thing: The Mersenne Twister has been generalized to 64 + ;; bits, and seems likely to be generalized to any future common CPU + ;; word width as well. Thus, it should be straightforward to + ;; implement this as "Return one sample from the MT variant + ;; corresponding to SB!VM:N-WORD-BITS." + ;; + ;; Meanwhile: Mock that up by pasting together as many samples from + ;; the 32-bit Mersenne Twister as necessary. + #.(ecase sb!vm:n-word-bits + (32 '(%random32 state)) + (64 '(logior + (%random32 state) + (ash (%random32 state) 32))))) ;;; Handle the single or double float case of RANDOM. We generate a ;;; float between 0.0 and 1.0 by clobbering the significand of 1.0 @@ -176,10 +197,16 @@ (defun %random-single-float (arg state) (declare (type (single-float (0f0)) arg) (type random-state state)) + ;; KLUDGE: The hardwired-to-32 hackery here could be replaced by a + ;; call to %RANDOM-BITS if there were sufficiently smart + ;; DEFTRANSFORMs for it, but in sbcl-1.0.4.epsilon it looks as + ;; though it would be a performance disaster. + (aver (<= sb!vm:single-float-digits 32)) (* arg (- (make-single-float - (dpb (ash (random-chunk state) - (- sb!vm:single-float-digits n-random-chunk-bits)) + (dpb (ash + (%random32 state) + (- sb!vm:single-float-digits 32)) sb!vm:single-float-significand-byte (single-float-bits 1.0))) 1.0))) @@ -187,25 +214,21 @@ (double-float 0d0)) %random-double-float)) -;;; 32-bit version -#!+nil -(defun %random-double-float (arg state) - (declare (type (double-float (0d0)) arg) - (type random-state state)) - (* (float (random-chunk state) 1d0) (/ 1d0 (expt 2 32)))) - ;;; 53-bit version #!-x86 (defun %random-double-float (arg state) (declare (type (double-float (0d0)) arg) (type random-state state)) + ;; KLUDGE: As in %RANDOM-SIMNGLE-FLOAT, as of sbcl-1.0.4.epsilon + ;; calling %RANDOM-BITS doesn't look reasonable, so we bang bits. + (aver (<= sb!vm:single-float-digits 32)) (* arg (- (sb!impl::make-double-float - (dpb (ash (random-chunk state) - (- sb!vm:double-float-digits n-random-chunk-bits 32)) + (dpb (ash (%random32 state) + (- sb!vm:double-float-digits 64)) sb!vm:double-float-significand-byte (sb!impl::double-float-high-bits 1d0)) - (random-chunk state)) + (%random32 state)) 1d0))) ;;; using a faster inline VOP @@ -217,13 +240,13 @@ (* arg (- (sb!impl::make-double-float (dpb (ash (sb!vm::random-mt19937 state-vector) - (- sb!vm:double-float-digits n-random-chunk-bits + (- sb!vm:double-float-digits + n-random-mt19937-bits sb!vm:n-word-bits)) sb!vm:double-float-significand-byte (sb!impl::double-float-high-bits 1d0)) (sb!vm::random-mt19937 state-vector)) 1d0)))) - ;;;; random integers @@ -276,9 +299,9 @@ until (<= ,raw-mersenne-output ,inclusive-limit-once) finally (return ,raw-mersenne-output)))) -;;; an UNSIGNED-BYTE of N-CHUNKS chunks sampled from the Mersenne twister -(declaim (inline %random-chunks)) -(defun %random-chunks (n-chunks state) +;;; an UNSIGNED-BYTE of N-WORDS words sampled from the Mersenne twister +(declaim (inline %random-words)) +(defun %random-words (n-words state) ;; KLUDGE: This algorithm will cons O(N^2) words when constructing ;; an N-word result. To do better should be fundamentally easy, we ;; just need to do some low-level hack preallocating the bignum and @@ -295,23 +318,24 @@ ;; the previous RNG author didn't have some subtle reason to need ;; RANDOM-INTEGER-OVERLAP that we know not of, we just concatenate ;; chunks. - (loop repeat n-chunks - for result = 0 then (logior (ash result n-random-chunk-bits) - (random-chunk state)) + (loop repeat n-words + for result = 0 then (logior (ash result sb!vm:n-word-bits) + (%random-word state)) finally (return result))) ;;; an UNSIGNED-BYTE of N-BITS bits sampled from the Mersenne twister (declaim (inline %random-bits)) (defun %random-bits (n-bits state) - (multiple-value-bind (n-full-chunks n-extra-bits) - (floor n-bits n-random-chunk-bits) - (let ((full-chunks (%random-chunks n-full-chunks state))) + (multiple-value-bind (n-full-words n-extra-bits) + (floor n-bits sb!vm:n-word-bits) + (let ((full-chunks (%random-words n-full-words state))) (if (zerop n-extra-bits) full-chunks (logior full-chunks - (ash (logand (random-chunk state) + (ash (logand (%random-word state) (1- (ash 1 n-extra-bits))) - (* n-full-chunks n-random-chunk-bits))))))) + (* n-full-words + sb!vm:n-word-bits))))))) ;;; the guts of (RANDOM (1+ INCLUSIVE-LIMIT)) (defun %inclusive-random-integer (inclusive-limit state) @@ -328,12 +352,11 @@ (declaim (maybe-inline %inclusive-random-fixnum)) (defun %inclusive-random-fixnum (inclusive-limit state) (declare (type (and fixnum unsigned-byte) inclusive-limit)) - (aver (<= inclusive-limit most-positive-random-chunk)) (let (;; If this calculation needs to be optimized further, a good ;; start might be a DEFTRANSFORM which picks off the case of ;; constant LIMIT and precomputes the MASK at compile time. (mask (%inclusive-random-integer-mask inclusive-limit))) - (%inclusive-random-integer-accept-reject (logand (random-chunk state) mask) + (%inclusive-random-integer-accept-reject (logand (%random-word state) mask) inclusive-limit))) ;;;; outer, dynamically-typed interface |