Hello Racketeers,
going through some more possible optimizations of my side projects, I
encountered a different behavior of unsafe-flvector-set! between BC and
CS implementations:
==== CUT HERE ====
#lang racket
(require racket/unsafe/ops
racket/flonum)
(define flv (make-flvector 10))
(for ((i (in-range 10)))
(unsafe-flvector-set! flv i i))
(for ((i (in-range 10)))
(display (~a #:width 4 (unsafe-flvector-ref flv i))))
(newline)
==== CUT HERE ====
$ racket test-flvector.rkt
SIGSEGV MAPERR si_code 1 fault on addr 0x9
Aborted (core dumped)
$ racketcs test-flvector.rkt
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0
$
The SIGSEGV is expected behavior (although might not get triggered every
time). The latter looks like implicit fx->fl operation.
Changing to safe flvector-set! results in expected contract violation
with both variants:
$ racketcs test-flvector.rkt
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0
$ racket test-flvector.rkt
flvector-set!: contract violation
expected: flonum?
given: 0
argument position: 3rd
other arguments...:
(flvector 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0)
0
context...:
"/home/joe/Projects/Programming/TD4/test-flvector.rkt": [running body]
temp35_0
for-loop
run-module-instance!
perform-require!
$ racketcs test-flvector.rkt
flvector-set!: contract violation
expected: flonum?
given: 0
context...:
/home/joe/Projects/Programming/racket-lang/racket/racket/collects/racket/private/for.rkt:1534:9
body of "/home/joe/Projects/Programming/TD4/test-flvector.rkt"
$
I assume that CS' unsafe-flvector-set! is actually pretty safe when it
comes to flonum-convertible numbers. It might be a bit faster because it
lacks the contract, but definitely it is not a "low level" variant.
Also given the fact that unsafe-fl+ and others give no performance
advantage (the opposite is true for well-written algorithms), maybe the
performance guide and unsafe ops documentation should get an update
before CS becomes the default implementation.
Any thoughts?
Cheers,
Dominik
--
You received this message because you are subscribed to the Google Groups
"Racket Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to racket-users+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/racket-users/c39293d0-51fa-41d8-3e0e-1fd99bca59ae%40trustica.cz.
