Re: NDSolve doesn't stop
- To: mathgroup at smc.vnet.net
- Subject: [mg74333] Re: NDSolve doesn't stop
- From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
- Date: Mon, 19 Mar 2007 01:58:52 -0500 (EST)
- Organization: The Open University, Milton Keynes, UK
- References: <etikd4$j5c$1@smc.vnet.net>
bar at ANTYSPAM.ap.krakow.pl wrote: > I have a problem with PDE solving using NDSolve > > tmax is the stop time > When I put tmax=21 NDSolve works very quickly (less than 1s) > When I put tmax=22 NDSolve never ends without any error/warning > > notebook file is "not readable" so I put it on www > > http://robox.ap.krakow.pl/~bar/pde.nb > > (file is less than 10kB) > > Could Someone help me ? > Regards Olaf > tmax = 20 ==> no warning message issued (indeed for any 0 < tmax <) ========= {{ET -> InterpolatingFunction[{{0., 20.}, {0., 1.}}, <>], FI -> \ InterpolatingFunction[{{0., 20.}, {0., 1.}}, <>]}} tmax = 21 ==> a warning message is issued: it might be worth reading it ========= NDSolve::"eerr" : "Warning: Scaled local spatial error estimate of (159.0346060966196) at (t) = (21.) in the direction of independent variable (x) is much greater than prescribed error tolerance. Grid spacing with (15) points may be too large to achieve the desired accuracy or precision. A singularity may have formed or you may want to specify a smaller grid spacing using the MaxStepSize or MinPoints options. More... {{ET -> InterpolatingFunction[{{0., 21.}, {0., 1.}}, <>], FI -> \ InterpolatingFunction[{{0., 21.}, {0., 1.}}, <>]}} tmax = 22 ==> things are going awry ========= [aborted] tmax = 23 ==> a warning message is issued: it might be worth reading it ========= NDSolve::"eerr" : "Warning: Scaled local spatial error estimate of (12.594134737787265) at (t) = (23.) in the direction of independent variable (x) is much greater than prescribed error tolerance. Grid spacing with (15) points may be too large to achieve the desired accuracy or precision. A singularity may have formed or you may want to specify a smaller grid spacing using the MaxStepSize or MinPoints options. More... {{ET -> InterpolatingFunction[{{0., 23.}, {0., 1.}}, <>], FI -> \ InterpolatingFunction[{{0., 23.}, {0., 1.}}, <>]}} tmax = 24 ==> no warning message issued ========= {{ET -> InterpolatingFunction[{{0., 24.}, {0., 1.}}, <>], FI -> \ InterpolatingFunction[{{0., 24.}, {0., 1.}}, <>]}} Regards, Jean-Marc