Re: Integrate a Piecewise funition, stange behaviour
- To: mathgroup at smc.vnet.net
- Subject: [mg53836] Re: [mg53799] Integrate a Piecewise funition, stange behaviour
- From: DrBob <drbob at bigfoot.com>
- Date: Sat, 29 Jan 2005 06:02:44 -0500 (EST)
- References: <200501280743.CAA00286@smc.vnet.net>
- Reply-to: drbob at bigfoot.com
- Sender: owner-wri-mathgroup at wolfram.com
Try posting in InputForm, so that the code isn't so garbled. http://www.eclecticdreams.net/DrBob/copy_as_inputform.htm Bobby On Fri, 28 Jan 2005 02:43:42 -0500 (EST), rik <rikypi_CREPA_SPAMMONE at libero.it> wrote: > hi, > i must evaluate this Integrate[]: > > int1 = Integrate[f, {w[2], - \[Infinity], \[Infinity]}] > > where: > > f = Piecewise[ > {{2/355, Inequality[2, LessEqual, w[2], LessEqual, 8] && > Inequality[4, LessEqual, w[2] + w[3], LessEqual, 12] && > Inequality[5, LessEqual, w[1] + w[2], LessEqual, 10] && w[1] > � 0 && w[3] � 0}}, 0] > > if i try to evaluate int, Mathematica (ver 5.1) takes 500-600 Mbyte of > ram and, after hours and hours, not arrives to any result :-( > > But if i apply Reduce to domain like this: > > red1 = Reduce[Inequality[2, LessEqual, w[2], LessEqual, 8] && > Inequality[4, LessEqual, w[2] + w[3], LessEqual, 12] && > Inequality[5, LessEqual, w[1] + w[2], LessEqual, 10] && w[1] > � 0 && w[3] � 0] > > and then i try to evaluate the follow command: > > Integrate[2/355 Boole[red1], {w[2], - \[Infinity], \[Infinity]}] > > > Mathematica do the calculation in few seconds!!! > > Why this behaviour? > > The two expression, f and "2/355 Boole[red1]", are not equal for the > Kernel of Mathematica? > > Is there a way to predict the complexity of a integral of a Piecewise > function? > > thanks and SORRY for my english > > Riccardo Piovosi > > > > -- DrBob at bigfoot.com www.eclecticdreams.net
- References:
- Integrate a Piecewise funition, stange behaviour
- From: rik <rikypi_CREPA_SPAMMONE@libero.it>
- Integrate a Piecewise funition, stange behaviour