Re: Piecewise bug in Mathematica 8.01?

*To*: mathgroup at smc.vnet.net*Subject*: [mg123134] Re: Piecewise bug in Mathematica 8.01?*From*: David Bailey <dave at removedbailey.co.uk>*Date*: Thu, 24 Nov 2011 06:56:55 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <jaio99$eqd$1@smc.vnet.net>

On 23/11/2011 12:17, Dario wrote: > Hello everyone > > I'm currently simulating some turbulent processes that incorporate a > large number of random steps. > I used Mathematica's 8.01 Piecewise to produce a function that has > different (random) values at different times. This function is then > used to calculate some differential equations. > Through some debugging I figured out that there is something wrong > with Mathematica's Piecewise when a large number of intervals is used. > Here is the isolated piece of code that I use to generate the random > values function. > > ****************************************************************** > list3 = {}; > list4 = {}; > j = 0; > Maxt = 40000; > dt = 1; > list3 = Table[RandomReal[{0.01, 0.03}], {i, 0, Maxt, dt}]; > list4 = Table[j< t<= j + dt, {j, 0, Maxt, dt}]; > anoise = Thread[{list3, list4}]; > a = Piecewise[anoise]; > Plot[a, {t, 0, Maxt}] > ***************************************************************** > > The problem I detected has to do with the number of intervals that > Piecewise uses, in this specific case is defined by Maxt. > If Maxt is bigger then 45000 then Mathematica crashes and all values > in memory are lost. > I've tried this in different PCs with different OS (Windows 7 and > Linux) and the same thing happens. > I've also tried to play around with $MaxPiecewiseCases but still no > luck. > Does someone has any idea what might be causing this? > > Best Regards > D=E1rio Passos > I reproduced it with 8.04 on 64-bit Windows. Clearly it is a bug - I suggest you report it through Wolfram support. David Bailey http://www.dbaileyconsultancy.co.uk