Hello, Manuel,
I noted another peculiarity with 4.5a in regards to srfi27. The
random-source-make-integers creates a generator that always returns bignums
even if the range is well within a fixnum. I was able to correct this by
altering mrg32k3a-c.srfi so that the gambit optimization declarations were
translated into bigloo type declarations and flonum specific arithmetic
operations. My changes are below. Is this something that we can include in 4.5a?
Thanks,Joe
; 54-BIT FLONUM IMPLEMENTATION OF THE "MRG32K3A"-GENERATOR
; ========================================================
;
; sebastian.eg...@philips.com, 2002.
;
; This code is a floating point implementation in Scheme of Pierre L'Ecuyer's
; MRG32k3a generator. The implementation runs under the Gambit 3.0 Scheme
; system. It makes use of Gambit's f64vector. The code is based on Brad
; Lucier's code for this generator. Please refer to Brad's original posting
; in the SRFI-27 discussion archive and to his posting of an optimization.
;
; compliance:
; Scheme R5RS with flonums covering at least {-2^53..2^53-1} exactly.
; In addition: declare f64vector ##fixnum?
;
; loading this file into Gambit 3.0:
; (load "mrg32k3a-2.scm")
;
; history of this file:
; SE, 18-Mar-2002: initial version
; SE, 25-Mar-2002: adapted to new interface
; SE, 04-Apr-2002: debugged; simplified
; SE, 10-Apr-2002: incorporated Brad Lucier's optimizations
; the actual generator
(define (mrg32k3a-random-m1 state) ; from Brad Lucier
(let* ((x10 (-fl (*fl 1403580.0 (f64vector-ref state 1))
(*fl 810728.0 (f64vector-ref state 2))))
(y10 (-fl x10 (*fl (floorfl (/fl x10 4294967087.0)) 4294967087.0)))
(x20 (-fl (*fl 527612.0 (f64vector-ref state 3))
(*fl 1370589.0 (f64vector-ref state 5))))
(y20 (-fl x20 (*fl (floorfl (/fl x20 4294944443.0)) 4294944443.0)))
(dx (-fl y10 y20))
(dy (-fl dx (*fl (floorfl (/fl dx 4294967087.0)) 4294967087.0))))
(f64vector-set! state 5 (f64vector-ref state 4))
(f64vector-set! state 4 (f64vector-ref state 3))
(f64vector-set! state 3 y20)
(f64vector-set! state 2 (f64vector-ref state 1))
(f64vector-set! state 1 (f64vector-ref state 0))
(f64vector-set! state 0 y10)
dy))
; interface to 'random.scm'
(define (mrg32k3a-pack-state unpacked-state)
(list->f64vector (map exact->inexact (vector->list unpacked-state))))
(define (mrg32k3a-unpack-state state)
(list->vector (map inexact->exact (f64vector->list state))))
(define (mrg32k3a-random-range::obj)
(if (fixnum? 4294967087)
4294967087
536870911)) ; 2^29-1
(define (mrg32k3a-random-integer::long state range::long) ; from Brad Lucier
(let* ((n::double (fixnum->flonum range))
(q::double (floorfl (/fl 4294967087.0 n)))
(qn::double (*fl q n)))
(do ((x::double (mrg32k3a-random-m1 state) (mrg32k3a-random-m1 state)))
((<fl x qn)
(flonum->fixnum (floorfl (/fl x q)))))))
(define (mrg32k3a-random-real state)
(*fl 0.0000000002328306549295728 (+fl 1.0 (mrg32k3a-random-m1 state))))
