Re: Re: slow integration

*To*: mathgroup at smc.vnet.net*Subject*: Re: [mg29958] Re: slow integration*From*: Tomas Garza <tgarza01 at prodigy.net.mx>*Date*: Tue, 24 Jul 2001 00:02:30 -0400 (EDT)*References*: <200107180608.CAA18960@smc.vnet.net> <9j65j1$2gh$1@smc.vnet.net> <200107200728.DAA05639@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

After reading your message, I'm also sure I don't understand your problem. You say "the integral is evaluated without delay": In[1]:= > Timing[InputForm[Integrate[Erf[400 (z/x-.002)],{x,0,.03}]]] > Out[1]= > {0.45 Second,Integrate[Erf[400*(-0.002 + z/x)], {x, 0, 0.03}]} But, is this an evaluation or just writing back what you gave as input? Tomas Garza Mexico City ----- Original Message ----- From: "Joshua A. Solomon" <J.A.Solomon at city.ac.uk> To: mathgroup at smc.vnet.net Subject: [mg29958] Re: slow integration > I'm not sure that you really understand the problem. (I *am* sure that I do > not understand the problem.) Note that, without the Gaussian factor in the > integrand, the integral is evaluated without delay: > > In[1]:= > Timing[InputForm[Integrate[Erf[400 (z/x-.002)],{x,0,.03}]]] > Out[1]= > {0.45 Second,Integrate[Erf[400*(-0.002 + z/x)], {x, 0, 0.03}]} > > > On 19/7/01 9:26 am, in article 9j65j1$2gh$1 at smc.vnet.net, "Tomas Garza" > <tgarza01 at prodigy.net.mx> wrote: > > > You will not get any result. I guess the problem is that Erf[z] doesn't have > > a closed form and it remains expressed as a definite integral. > > > > Tomas Garza > > Mexico City > > > > > > ----- Original Message ----- > > From: "Joshua A. Solomon" <J.A.Solomon at city.ac.uk> To: mathgroup at smc.vnet.net > To: mathgroup at smc.vnet.net > > Subject: [mg29958] slow integration > > > > > >> In[1]:= > >> $Version > >> Out[1]= > >> 4.1 for Power Macintosh (November 2, 2000) > >> > >> Does anyone out there understand why, after two hours, the following still > >> hasn't produced any output? > >> > >> In[2]:= > >> Integrate[E^(-100000 (.03-x)^2)Erf[400 (z/x-.002)],{x,0,.03}] > >> > >> js > >> -- > >> Joshua A. Solomon > >> Department of Optometry and Visual Science > >> City University > >> London EC1V 0HB > >> Voice: (44) 20 7040 0192 > >> Secretary/Fax: (44) 20 7040 0182 > >> J.A.Solomon at city.ac.uk > >> http://www.staff.city.ac.uk/~solomon > >> > >> > > > > > >

**References**:**slow integration***From:*"Joshua A. Solomon" <J.A.Solomon@city.ac.uk>

**Re: slow integration***From:*"Joshua A. Solomon" <J.A.Solomon@city.ac.uk>