click to view the MPEG movie (cliquez pour voir le film MPEG)

N-body problem integration (N=4: one star, one heavy planet and one light planet with a satellite) computed with 3 different optimization options on the same computer (sensitivity to rounding-off errors) [Intégration du problème des N-corps (N=4: une étoile, une planète lourde et une planète légère avec un satellite) calculé avec 3 options d'optimisation différentes (sensibilité aux erreurs d'arrondi)].




The same program is compiled 3 times with 3 different optimization options and then is run with exactly the same initial conditions -see bottom left picture- (the computer used is a SGI Power-Challenge M -75 MHz R8000 Processor- under IRIX 6.2 with C 7.0):



In this example, "-O1" et "-O2" give the same forecasts (Red+Green = Yellow), when "-O3" (the most aggressive optimization) gives very different results.


(CMAP28 WWW site: this page was created on 02/04/1997 and last updated on 02/26/2022 19:02:28 -CET-)



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