Re: Applying Bounding Limits to PDE Solution Variables
On Tue, Aug 2, 2016 at 2:02 PM, Campbell, Ian wrote: > > I've tried the mean-square and RMS values, but they're both orders of > magnitude away from the residual returned by '.sweep'. As such, can you > please tell me the formula used by '.sweep' to compute the residual, so that > I may use the same one? I think it's the L2 norm of "A * x - b" without any normalization, where x is the variable value before the linear solve. See, https://github.com/usnistgov/fipy/blob/develop/fipy/solvers/solver.py#L135 -- Daniel Wheeler ___ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
RE: Applying Bounding Limits to PDE Solution Variables
Hi Daniel, Thank you very much for your prompt reply. I'm manually trying to implement the bound-checking feature immediately following a sweep, as you've suggested. As an initial step towards this, I need to manually compute my own residual and compare to that computed via '.sweep' in FiPy. I've tried the mean-square and RMS values, but they're both orders of magnitude away from the residual returned by '.sweep'. As such, can you please tell me the formula used by '.sweep' to compute the residual, so that I may use the same one? With best regards, - Ian -Original Message- From: fipy-boun...@nist.gov [mailto:fipy-boun...@nist.gov] On Behalf Of Daniel Wheeler Sent: 02 August 2016 15:57 To: Multiple recipients of list Subject: Re: Applying Bounding Limits to PDE Solution Variables Hi Ian, Sorry, there isn't any way to do this as an implicit command in FiPy, whether as a simple reset during sweeping or as a fully implicit constraint in the equations. Of course, you can always try these techniques explicitly in the Python code or in the design of the equations. I agree that It would be nice to have a one sided constraint syntactically in FiPy, but I'm not sure how best to make that work internally. Cheers, Daniel On Tue, Aug 2, 2016 at 10:46 AM, Campbell, Ian wrote: > Hi All, > > > > I would like to prevent the CellVariables I am solving for from ever > reaching physically-meaningless and incorrect values, such as > concentrations becoming negative. Is there a way to do this? > > > > The most natural place I could think of it being is an argument in > CellVariable declaration, such as “phi = CellVariable(mesh = mesh2d, > value = phi_0, upperlimit = 10**7, lowerlimit = 0)”. However, I > haven’t found such an option there or in any of the FiPy documentation. > > > > With best regards, > > > > - Ian > > > ___ > fipy mailing list > fipy@nist.gov > http://www.ctcms.nist.gov/fipy > [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ] > -- Daniel Wheeler ___ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ] ___ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
Re: Applying Bounding Limits to PDE Solution Variables
Hi Ian, Sorry, there isn't any way to do this as an implicit command in FiPy, whether as a simple reset during sweeping or as a fully implicit constraint in the equations. Of course, you can always try these techniques explicitly in the Python code or in the design of the equations. I agree that It would be nice to have a one sided constraint syntactically in FiPy, but I'm not sure how best to make that work internally. Cheers, Daniel On Tue, Aug 2, 2016 at 10:46 AM, Campbell, Ian wrote: > Hi All, > > > > I would like to prevent the CellVariables I am solving for from ever > reaching physically-meaningless and incorrect values, such as concentrations > becoming negative. Is there a way to do this? > > > > The most natural place I could think of it being is an argument in > CellVariable declaration, such as “phi = CellVariable(mesh = mesh2d, value = > phi_0, upperlimit = 10**7, lowerlimit = 0)”. However, I haven’t found such > an option there or in any of the FiPy documentation. > > > > With best regards, > > > > - Ian > > > ___ > fipy mailing list > fipy@nist.gov > http://www.ctcms.nist.gov/fipy > [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ] > -- Daniel Wheeler ___ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
Applying Bounding Limits to PDE Solution Variables
Hi All, I would like to prevent the CellVariables I am solving for from ever reaching physically-meaningless and incorrect values, such as concentrations becoming negative. Is there a way to do this? The most natural place I could think of it being is an argument in CellVariable declaration, such as "phi = CellVariable(mesh = mesh2d, value = phi_0, upperlimit = 10**7, lowerlimit = 0)". However, I haven't found such an option there or in any of the FiPy documentation. With best regards, - Ian ___ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
