Thanks! Your patch has been applied.
Marc
On 15-Jan-09, at 12:26 PM, Bradley Lucier wrote:
A student was trying to use Gambit for a Monte-Carlo simulation, so I looked at the speed of generating inexact pseudo-random numbers.
This patch adds a procedure
(random-source-make-f64vectors rs #!optional (p (macro-absent-obj))
that returns an f64vector of pseudo-random inexact numbers. The purpose of this procedure is to avoid the trampoline in the very common case when inexact reals are needed in groups by an algorithm.
It also adds the predefined procedure random-f64vector.
There is some amount of duplication in the internal procedure
(make-f64vectors precision)
in order to have an allocation-free path for the generation of the random reals, so that the only memory allocated is for the f64vector itself.
In one place I changed
(fl/ (fl+ (macro-inexact-+1) (f64vector-ref state 6))(macro-m1-plus-1-inexact)))))
(fl* (fl+ (macro-inexact-+1) (f64vector-ref state 6))(macro-inv-m1-plus-1-inexact)))))because the division wasn't necessary to preserve the correctness of the algorithm. (The divisions are necessary in advance-state! to preserve the correctness of the algorithm.)
I changed advance-state! to avoid the final flfloor (it seems that flfloor, flonum->fixnum, ..., take a relatively long time on my Core 2 Duo compared to the usual addition, multiplication, ...); the new code still avoids boxing flonums. I also made state a local variable because the register allocator kept reloading it into registers, stack slots, etc., from the closure.
And then I tried to document this stuff.
I noticed that the optional precision parameter wasn't documented; was that intentional?
Brad
Tests:
With test-random-reals.scm given by
(declare (standard-bindings)(extended-bindings)(block)(not safe))
(define (make-random-f64vector n) (let ((result (make-f64vector n))) (do ((i (fx- n 1) (fx- i 1))) ((fx< i 0) result) (f64vector-set! result i (random-real)))))
I get with current head
frying-pan:~/programs/gambc-v4_4_0-devel> gsi Gambit v4.4.0
(load "test-random-reals")
"/home/lucier/programs/gambc-v4_4_0-devel/test-random-reals.o13"
(define a (time (make-f64vector 1000000)))
(time (make-f64vector 1000000)) 7 ms real time 4 ms cpu time (0 user, 4 system) 1 collection accounting for 1 ms real time (0 user, 0 system) 8000048 bytes allocated 1984 minor faults no major faults
(define a (time (make-random-f64vector 1000000)))
(time (make-random-f64vector 1000000)) 162 ms real time 160 ms cpu time (144 user, 16 system) 2 collections accounting for 1 ms real time (0 user, 0 system) 40000048 bytes allocated 4981 minor faults no major faults
and with the changes I get
frying-pan:~/programs/gambc-v4_4_0-devel> gsi/gsi Gambit v4.4.0
(load "test-random-reals")
"/home/lucier/programs/gambc-v4_4_0-devel/test-random-reals.o13"
(define a (time (make-f64vector 1000000)))
(time (make-f64vector 1000000)) 6 ms real time 4 ms cpu time (0 user, 4 system) 1 collection accounting for 0 ms real time (0 user, 0 system) 8000048 bytes allocated 1982 minor faults no major faults
(define a (time (make-random-f64vector 1000000)))
(time (make-random-f64vector 1000000)) 132 ms real time 132 ms cpu time (120 user, 12 system) 2 collections accounting for 1 ms real time (0 user, 0 system) 40000048 bytes allocated 4981 minor faults no major faults
(define a (time (random-f64vector 1000000)))
(time (random-f64vector 1000000)) 73 ms real time 72 ms cpu time (64 user, 8 system) no collections 8000048 bytes allocated 1954 minor faults no major faults
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