> On Jan 28, 2015, at 12:54 PM, <[email protected]> > <[email protected]> wrote: > > Hi, > > I have a F90 suite that uses the petsc and runs for structured and > unstructured matrices. For the unstructured we do not see the change at tiny > decimal places but in the structured we do.
What data is the change in? A solution? Some derived quantity of the solution? Or in a residual? Depending on what the difference is in generally that seems a very small difference to me. > The same solver is being used - GMRES. The tolerance should be 1e-10 in both > cases but I can check in case there is a mistake. You can try using KSP and SNES tolerances of 1e-12 to see if you get closer match -ksp_rtol 1.e-12 -snes_rtol 1.e-12 > > Carol > > Dr Carol Brickley > BSc,PhD,ARCS,DIC,MBCS > > Senior Software Engineer > Applied Computer Science > DS+T, > AWE > Aldermaston > Reading > Berkshire > RG7 4PR > > Direct: 0118 9855035 > > -----Original Message----- > From: Barry Smith [mailto:[email protected]] > Sent: 28 January 2015 18:52 > To: Brickley Carol AWE > Cc: [email protected] > Subject: EXTERNAL: Re: [petsc-users] F90 to petsc 3.4.3 interface - loss of > accuracy > > >> On Jan 28, 2015, at 12:39 PM, <[email protected]> >> <[email protected]> wrote: >> >> Hi, >> >> Does anyone find loss of accuracy between F90 code and Petsc 3.4.3 C codes? >> I am noticing that some of my data is returning 9.99999997e-13 instead of >> 1.00000000e-12 for example. > > I am not sure exactly what your question is. Do you have two codes a F90 > code without PETSc and a PETSc based C code? What is the data that is > different? Is it solutions, residual values, ...? This kind of small > difference can often be caused by different tolerances used during the > iterative solvers. We'll need more information in order to make any > suggestions. > > Barry > >> >> Carol >> >> Dr Carol Brickley >> BSc,PhD,ARCS,DIC,MBCS >> >> Senior Software Engineer >> Applied Computer Science >> DS+T, >> AWE >> Aldermaston >> Reading >> Berkshire >> RG7 4PR >> >> Direct: 0118 9855035 >> >> ___________________________________________________ >> ____________________________ The information in this email and in any >> attachment(s) is commercial in confidence. If you are not the named >> addressee(s) or if you receive this email in error then any distribution, >> copying or use of this communication or the information in it is strictly >> prohibited. Please notify us immediately by email at >> admin.internet(at)awe.co.uk, and then delete this message from your >> computer. While attachments are virus checked, AWE plc does not accept any >> liability in respect of any virus which is not detected. AWE Plc Registered >> in England and Wales Registration No 02763902 AWE, Aldermaston, Reading, RG7 >> 4PR >> > > > ___________________________________________________ > ____________________________ > > The information in this email and in any attachment(s) is > commercial in confidence. If you are not the named addressee(s) > or > if you receive this email in error then any distribution, copying or > use of this communication or the information in it is strictly > prohibited. Please notify us immediately by email at > admin.internet(at)awe.co.uk, and then delete this message from > your computer. While attachments are virus checked, AWE plc > does not accept any liability in respect of any virus which is not > detected. > > AWE Plc > Registered in England and Wales > Registration No 02763902 > AWE, Aldermaston, Reading, RG7 4PR
