spectral-norm Racket #3 program
source code
#lang racket/base
;; The Computer Language Benchmarks Game
;; https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
;; Translated from Mike Pall's Lua version.
;; Parallelized by Sam Tobin-Hochstadt
(require racket/cmdline racket/future
racket/require (for-syntax racket/base)
(filtered-in (λ (name) (regexp-replace #rx"unsafe-" name ""))
racket/unsafe/ops)
(only-in racket/flonum make-flvector))
(define-syntax-rule (for/par k ([i N]) b)
(let ([stride (fxquotient N k)])
(define fs
(for/list ([n k])
(future (λ () (for ([i (in-range (fx* n stride) (fxmin N (fx* (fx+ n 1) stride)))]) b)))))
(for-each touch fs)))
;; the big let improves performance by about 20%
(let* ()
(define N (command-line #:args (n) (string->number n)))
(define C (processor-count))
(define (A i j)
(let ([ij (fx+ i j)])
(fl/ 1.0 (fl+ (fl* (fl* (fx->fl ij)
(fx->fl (fx+ ij 1)))
0.5)
(fx->fl (fx+ i 1))))))
(define (Av x y N)
(for/par C ([i N])
(flvector-set!
y i
(let L ([a 0.0] [j 0])
(if (fx= j N) a
(L (fl+ a (fl* (flvector-ref x j) (A i j)))
(fx+ j 1)))))))
(define (Atv x y N)
(for/par C ([i N])
(flvector-set!
y i
(let L ([a 0.0] [j 0])
(if (fx= j N) a
(L (fl+ a (fl* (flvector-ref x j) (A j i)))
(fx+ j 1)))))))
(define (AtAv x y t N) (Av x t N) (Atv t y N))
(define u (make-flvector N 1.0))
(define v (make-flvector N))
(define t (make-flvector N))
(for ([i (in-range 10)])
(AtAv u v t N) (AtAv v u t N))
(displayln (real->decimal-string
(flsqrt
(let L ([vBv 0.0] [vv 0.0] [i 0])
(if (fx= i N) (fl/ vBv vv)
(let ([ui (flvector-ref u i)] [vi (flvector-ref v i)])
(L (fl+ vBv (fl* ui vi))
(fl+ vv (fl* vi vi))
(fx+ i 1))))))
9)))
notes, command-line, and program output
NOTES:
64-bit Ubuntu quad core
Racket v8.14 [cs].
Fri, 06 Sep 2024 19:18:22 GMT
MAKE:
make: *** No rule to make target 'spectralnorm.racket-3.racket_run'. Stop.
0.05s to complete and log all make actions
COMMAND LINE:
/opt/src/./racket-8.14/bin/racket spectralnorm.racket-3.racket 5500
PROGRAM OUTPUT:
1.274224153