Can you send the code that reproduces this behavior? Barry
On Jun 25, 2014, at 4:37 PM, Arthur Kurlej <[email protected]> wrote: > Hi Barry, > > So for the matrix C that I am currently testing (size 162x162), the condition > number is roughly 10^4. > > For reference, I'm porting MATLAB code into PETSc, and for one processor, the > PETSc b vector is roughly equivalent to the MATLAB b vector. So I know that > for one processor, my program is performing as expected. > > I've included examples below of values for b (also of size 162), ranging from > indices 131 to 141. > > #processors=1: > 0 > 1.315217173959314e-20 > 1.315217173959314e-20 > 4.843201487740107e-17 > 4.843201487740107e-17 > 8.166104700666665e-14 > 8.166104700666665e-14 > 6.303834267553249e-11 > 6.303834267553249e-11 > 2.227932688485483e-08 > 2.227932688485483e-08 > > # processors=2: > 5.480410831461926e-22 > 2.892553944350444e-22 > 2.892553944350444e-22 > 7.524038923310717e-24 > 7.524038923214420e-24 > -3.340766769043093e-26 > -7.558372155761972e-27 > 5.551561288838557e-25 > 5.550551546879874e-25 > -1.579397982093437e-22 > 2.655766754178065e-22 > > # processors = 4: > 5.480410831461926e-22 > 2.892553944351728e-22 > 2.892553944351728e-22 > 7.524092205125593e-24 > 7.524092205125593e-24 > -2.584939414228212e-26 > -2.584939414228212e-26 > 0 > 0 > -1.245940797657998e-23 > -1.245940797657998e-23 > > # processors = 8: > 5.480410831461926e-22 > 2.892553944023035e-22 > 2.892553944023035e-22 > 7.524065744581494e-24 > 7.524065744581494e-24 > -2.250265175188197e-26 > -2.250265175188197e-26 > -6.543127892265160e-26 > 1.544288143499193e-317 > 8.788794008375919e-25 > 8.788794008375919e-25 > > > Thanks, > Arthur > > > > On Wed, Jun 25, 2014 at 4:06 PM, Barry Smith <[email protected]> wrote: > > How different are the values in b? Can you send back a few examples of the > different b’s? Any idea of the condition number of C? > > Barry > > On Jun 25, 2014, at 3:10 PM, Arthur Kurlej <[email protected]> wrote: > > > Hi all, > > > > While running my code, I have found that MatMult() returns different values > > depending on the number of processors I use (and there is quite the > > variance in the values). > > > > The setup of my code is as follows (I can go into more depth/background if > > needed): > > -Generate parallel AIJ matrix of size NxN, denoted as A > > -Retrieve parallel AIJ submatrix from the last N-1 rows&columns from A, > > denoted as C > > -Generate vector of length N-1, denoted as x > > -Find C*x=b > > > > I have already checked that A, C, and x are all equivalent when ran for any > > number of processors, it is only the values of vector b that varies. > > > > Does anyone have an idea about what's going on? > > > > > > Thanks, > > Arthur > > > >
