Hi , Thanks for the help. It was a random large number in a part of the vector I had not initialized, Subramanya
> From: [email protected] > To: [email protected] > CC: [email protected]; [email protected]; > [email protected] > Date: Sun, 14 Jul 2013 09:19:01 -0500 > Subject: Re: [Libmesh-users] Really Really Really Weird SNES behaviour > > Have you tried devel mode? It uses compiler flags similar to optimized mode > but leaves asserts on too. > > Otherwise, I agree with Cody that there may be an uninitialized value that is > silently being set to 0 in debug mode but contains garbage in optimized mode. > > -Ben > > > On Jul 14, 2013, at 7:26 AM, "Cody Permann" <[email protected]> wrote: > > > Sounds like a memory corruption problem. I know several users that are > > experts at writing code like that. > > > > Unfortunately, it can be difficult to track down on OS X due to a lack > > of working memory analysis tools. > > 1. Since this problem popped up after you changed your initial > > condition, you may just want to start by carefully looking at your > > code and thinking about cases where your variables might not be > > initialized, or where calculations could potentially produce underflow > > or overflow conditions. > > 2. If you have access to a Linux box, then you will have bounds > > checked STL containers at your disposal in debug mode. You'll also be > > able to run your code through valgrind. Both of those operations are > > relatively easy to perform. Let us know if you have any questions. > > > > Cody > > > > Sent from my iPhone > > > > On Jul 13, 2013, at 11:17 PM, subramanya sadasiva <[email protected]> > > wrote: > > > >> Hi, I am observing some really really really weird SNES behavior in my > >> SNESVI code called through Libmesh. This behaviour appeared after I > >> changed some initial conditions and only happens in an optimized build. I > >> am running this code on a Macbook pro running os x 10.8.. > >> When the debug code is run, the residuals computed for the initial > >> conditions provided give norms which are of the expected magnitude.. so > >> the SNES_Monitor output is, > >> solving the cahn hilliard time step 0 SNES Function norm > >> 8.223262421671e-01 1 SNES Function norm 3.793806858333e-03Nonlinear solve > >> did not converge due to DIVERGED_MAX_IT iterations 1 > >> The output from SNES_Monitor with the optimized code on the other hand is, > >> solving the cahn hilliard time step 0 SNES Function norm > >> 5.153882032022e+19 1 SNES Function norm 1.446612980133e+19Nonlinear solve > >> did not converge due to DIVERGED_MAX_IT iterations 1 > >> > >> Absolutely nothing else has changed in the code except that one code is > >> built with a debugging and one with an optimized version of the code. > >> Any ideas?Subramanya > >> ------------------------------------------------------------------------------ > >> See everything from the browser to the database with AppDynamics > >> Get end-to-end visibility with application monitoring from AppDynamics > >> Isolate bottlenecks and diagnose root cause in seconds. > >> Start your free trial of AppDynamics Pro today! > >> http://pubads.g.doubleclick.net/gampad/clk?id=48808831&iu=/4140/ostg.clktrk > >> _______________________________________________ > >> Libmesh-users mailing list > >> [email protected] > >> https://lists.sourceforge.net/lists/listinfo/libmesh-users > > > > ------------------------------------------------------------------------------ > > See everything from the browser to the database with AppDynamics > > Get end-to-end visibility with application monitoring from AppDynamics > > Isolate bottlenecks and diagnose root cause in seconds. > > Start your free trial of AppDynamics Pro today! > > http://pubads.g.doubleclick.net/gampad/clk?id=48808831&iu=/4140/ostg.clktrk > > _______________________________________________ > > Libmesh-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/libmesh-users ------------------------------------------------------------------------------ See everything from the browser to the database with AppDynamics Get end-to-end visibility with application monitoring from AppDynamics Isolate bottlenecks and diagnose root cause in seconds. Start your free trial of AppDynamics Pro today! http://pubads.g.doubleclick.net/gampad/clk?id=48808831&iu=/4140/ostg.clktrk _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
