[Git][cmucl/cmucl][rtoy-xoro-default] Modify random-state-jump to use 32-bit ints

[Raymond Toy]

Raymond Toy pushed to branch rtoy-xoro-default at cmucl / cmucl


Commits:
96c58393 by Raymond Toy at 2017-12-27T09:46:59-08:00
Modify random-state-jump to use 32-bit ints

Break the constants in the jump function into 32-bit chunks so we
operate on 32-bit integers instead of 64-bit integers.

This is a minor optimization.

- - - - -


1 changed file:

- src/code/rand-xoroshiro.lisp


Changes:

=====================================
src/code/rand-xoroshiro.lisp
=====================================
--- a/src/code/rand-xoroshiro.lisp
+++ b/src/code/rand-xoroshiro.lisp
@@ -485,9 +485,12 @@
 	(s1-1 0))
     (declare (type (unsigned-byte 32) s0-0 s0-1 s1-0 s1-1)
 	     (optimize (speed 3) (safety 0)))
-    (dolist (jump '(#xbeac0467eba5facb #xd86b048b86aa9922))
-      (declare (type (unsigned-byte 64) jump))
-      (dotimes (b 64)
+    ;; The constants are #xbeac0467eba5facb and #xd86b048b86aa9922,
+    ;; and we process these numbers starting from the LSB.  We want ot
+    ;; process these in 32-bit chunks, so word-reverse the constants.
+    (dolist (jump '(#xeba5facb #xbeac0467 #x86aa9922 #xd86b048b))
+      (declare (type (unsigned-byte 32) jump))
+      (dotimes (b 32)
 	(declare (fixnum b))
 	(when (logbitp b jump)
 	  (multiple-value-bind (x1 x0)



View it on GitLab: https://gitlab.common-lisp.net/cmucl/cmucl/commit/96c58393bebcf502919736ca2e00874ce46a6aee

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View it on GitLab: https://gitlab.common-lisp.net/cmucl/cmucl/commit/96c58393bebcf502919736ca2e00874ce46a6aee
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