Since Matt wrote a portable random number generator as the default random
number generator there should be no difference on any machine based on using
using a random right hand side.
Of course, as always, with different number of processes one will get
different results, even with Jacobi + Chebyshev because the random numbers
generated will be different with different number of processes, is this
important?
I think we should wait to hear from Jed before making any change but I am
comfortable with changing the default to use the random number generator.
Barry
> On May 17, 2016, at 11:21 AM, Mark Adams <[email protected]> wrote:
>
>
> On Sat, Aug 22, 2015 at 10:39 PM, Barry Smith <[email protected]> wrote:
>
> > On Aug 22, 2015, at 9:26 PM, Mark Adams <[email protected]> wrote:
> >
> > I would vote for (1).
> >
> > Also, I hope cheb->random is the default.
>
> Well then different machines will produce different convergence histories
> which is annoying for any kind of "no change" daily testing. Except for you,
> most of the rest of us don't like the random default, sorry :-)
>
> Well, this bit me and Garth Wells, among others I would guess.
>
> The problem is that RHS are often smooth and this leads to poor convergence
> to the highest eigenvalue. As an example on the new ex56, elasticity, cube,
> traction on one side, the history of the eigen estimator looks like this
> (appended). Garth mentioned that he uses 50 iterations in the eigen estimator
> (ie, a lot), and you can see why here, It looks converged at 44 iterations at
> ~1.42 and then pops up to ~1.72 very quickly. This is such a big jump that
> it overwhelms the common 1.05 safety factor. If you add
> -mg_levels_ksp_chebyshev_esteig_random you see nice smooth and fast
> convergence (appended).
>
> Note, the iteration number of this jump seems to be about linear in h, so
> this will fail with 50 iterations on a larger problem (this one has about 6M
> dof).
>
> Now, I guess I can put -mg_levels_ksp_chebyshev_esteig_random in the
> tutorials as suggested parameters and keep them out of the tests to avoid
> your issue with regression tests. Right?
>
> Mark
> ps, I'm sure Jed free climbed out of the pit, so you can use his rope.
>
>
> 39 KSP Residual norm 5.149666187461e+00 % max 1.423034674475e+00 min
> 5.820371669083e-04 max/min 2.444920626003e+03
> 40 KSP Residual norm 5.157885158697e+00 % max 1.423126042184e+00 min
> 5.557328840496e-04 max/min 2.560809487850e+03
> 41 KSP Residual norm 5.303627521687e+00 % max 1.423199352292e+00 min
> 5.313351872668e-04 max/min 2.678533977041e+03
> 42 KSP Residual norm 5.364384189061e+00 % max 1.423275534927e+00 min
> 5.062394822273e-04 max/min 2.811466874659e+03
> 43 KSP Residual norm 5.490412749639e+00 % max 1.423347554528e+00 min
> 4.823994222923e-04 max/min 2.950558165607e+03
> 44 KSP Residual norm 5.298532106786e+00 % max 1.423435653436e+00 min
> 4.630735554742e-04 max/min 3.073886721901e+03
> 45 KSP Residual norm 5.250150466693e+00 % max 1.444039693619e+00 min
> 4.458237353578e-04 max/min 3.239037267632e+03
> 46 KSP Residual norm 5.355091565702e+00 % max 1.597859894587e+00 min
> 4.296586330882e-04 max/min 3.718905595128e+03
> 47 KSP Residual norm 5.359212994059e+00 % max 1.694500733083e+00 min
> 4.115503583969e-04 max/min 4.117359391167e+03
> 48 KSP Residual norm 5.382627967217e+00 % max 1.715436978188e+00 min
> 3.945385500813e-04 max/min 4.347957830318e+03
> 49 KSP Residual norm 5.333511242816e+00 % max 1.719426018108e+00 min
> 3.791973408295e-04 max/min 4.534383111304e+03
> 50 KSP Residual norm 5.286785239032e+00 % max 1.720488275875e+00 min
> 3.655323031666e-04 max/min 4.706802274303e+03
>
> with -mg_levels_ksp_chebyshev_esteig_random
>
> 0 KSP Residual norm 4.587476885185e+05 % max 1.000000000000e+00 min
> 1.000000000000e+00 max/min 1.000000000000e+00
> 1 KSP Residual norm 5.000026676130e+05 % max 2.096521908651e-01 min
> 2.096521908651e-01 max/min 1.000000000000e+00
> 2 KSP Residual norm 2.383418066969e+06 % max 9.808897648348e-01 min
> 5.952257317564e-03 max/min 1.647929033478e+02
> 3 KSP Residual norm 2.574503036099e+06 % max 1.019204519789e+00 min
> 3.039124767415e-03 max/min 3.353611969855e+02
> 4 KSP Residual norm 2.458678036734e+06 % max 1.244548092713e+00 min
> 1.992498130768e-03 max/min 6.246169436720e+02
> 5 KSP Residual norm 2.344964690599e+06 % max 1.367637044108e+00 min
> 1.464901327469e-03 max/min 9.336035256864e+02
> 6 KSP Residual norm 2.331695060244e+06 % max 1.404943514389e+00 min
> 1.190280622651e-03 max/min 1.180346455830e+03
> 7 KSP Residual norm 2.271960219657e+06 % max 1.437957455093e+00 min
> 1.008722431370e-03 max/min 1.425523424853e+03
> 8 KSP Residual norm 2.292028741926e+06 % max 1.502852988492e+00 min
> 8.809546168835e-04 max/min 1.705936900369e+03
> 9 KSP Residual norm 2.233478095421e+06 % max 1.582008563628e+00 min
> 7.783319825046e-04 max/min 2.032562709986e+03
> 10 KSP Residual norm 2.217240790630e+06 % max 1.627791394511e+00 min
> 7.017777386360e-04 max/min 2.319525549035e+03
> 11 KSP Residual norm 2.253686552707e+06 % max 1.659357337462e+00 min
> 6.359067415045e-04 max/min 2.609435046303e+03
> 12 KSP Residual norm 2.327352703032e+06 % max 1.682006777543e+00 min
> 5.780023151159e-04 max/min 2.910034672103e+03
> 13 KSP Residual norm 2.258932746968e+06 % max 1.695221701128e+00 min
> 5.272335154902e-04 max/min 3.215314753940e+03
> 14 KSP Residual norm 2.146539128962e+06 % max 1.701712426981e+00 min
> 4.879541184491e-04 max/min 3.487443517005e+03
> 15 KSP Residual norm 2.146242364688e+06 % max 1.705375519134e+00 min
> 4.576872864507e-04 max/min 3.726071423917e+03
> 16 KSP Residual norm 2.160438533108e+06 % max 1.708650293977e+00 min
> 4.278996767955e-04 max/min 3.993109568984e+03
> 17 KSP Residual norm 2.184700124943e+06 % max 1.710853580610e+00 min
> 4.021751403604e-04 max/min 4.254001326580e+03
> 18 KSP Residual norm 2.148601462370e+06 % max 1.712408913049e+00 min
> 3.793690742988e-04 max/min 4.513833701954e+03
> 19 KSP Residual norm 2.195737087965e+06 % max 1.713723267846e+00 min
> 3.583883046289e-04 max/min 4.781749978199e+03
