[petsc-users] Linear iterative solver cannot converge

Matthew Knepley knepley at gmail.com
Fri May 18 05:16:46 CDT 2018 

On Fri, May 18, 2018 at 6:10 AM, Y. Shidi <ys453 at cam.ac.uk> wrote:

> Hello Matt,
>
> Thank you for your reply.
> It might due to that the email is too long.
> Below is the subsequent iterations.
>

1) If you are solving a PDE, GMRES+Jacobi is unlikely to be a scalable
solver.
    Note that your condition number is 10^7.

2) Requiring a residual norm below 1e-9 might not work. Your system looks
ill-conditioned,
    and that can magnify round-off errors. If you need more accuracy, you
could try iterative
    refinement, which would be to use one more step of Newton's method for
your linear problem,
    or equivalently, solve the same system again for a solution update with
the residual as the rhs.

  Thanks,

     Matt


> In general, the iterative solver is very sensitive to the system. We
>> recommend
>> starting with a solver that has worked before for someone by checking
>> the literature.
>>
> Ok, I will try to find it.
>
> Kind Regards,
> Shidi
>
> 411 KSP preconditioned resid norm 9.546868463763e-10 true resid norm
> 7.703880356970e-02 ||r(i)||/||b|| 1.217736363864e-01
> 411 KSP Residual norm 9.546868463763e-10 % max 1.574002896609e+02 min
> 1.541649904298e-05 max/min 1.020985952920e+07
> 412 KSP preconditioned resid norm 9.522037274646e-10 true resid norm
> 7.703756753884e-02 ||r(i)||/||b|| 1.217716826181e-01
> 412 KSP Residual norm 9.522037274646e-10 % max 1.582553544478e+02 min
> 1.541604620560e-05 max/min 1.026562533202e+07
> 413 KSP preconditioned resid norm 9.497398839135e-10 true resid norm
> 7.703634622699e-02 ||r(i)||/||b|| 1.217697521158e-01
> 413 KSP Residual norm 9.497398839135e-10 % max 1.591104211134e+02 min
> 1.541559807295e-05 max/min 1.032139138297e+07
> 414 KSP preconditioned resid norm 9.472950676296e-10 true resid norm
> 7.703513938163e-02 ||r(i)||/||b|| 1.217678444804e-01
> 414 KSP Residual norm 9.472950676296e-10 % max 1.599654896233e+02 min
> 1.541515456432e-05 max/min 1.037715768310e+07
> 415 KSP preconditioned resid norm 9.448690349674e-10 true resid norm
> 7.703394674743e-02 ||r(i)||/||b|| 1.217659593083e-01
> 415 KSP Residual norm 9.448690349674e-10 % max 1.608205599436e+02 min
> 1.541471562375e-05 max/min 1.043292421793e+07
> 416 KSP preconditioned resid norm 9.424615466266e-10 true resid norm
> 7.703276808042e-02 ||r(i)||/||b|| 1.217640962139e-01
> 416 KSP Residual norm 9.424615466266e-10 % max 1.616756320416e+02 min
> 1.541428116222e-05 max/min 1.048869099636e+07
> 417 KSP preconditioned resid norm 9.400723675537e-10 true resid norm
> 7.703160313689e-02 ||r(i)||/||b|| 1.217622548118e-01
> 417 KSP Residual norm 9.400723675537e-10 % max 1.625307058852e+02 min
> 1.541385112375e-05 max/min 1.054445800601e+07
> 418 KSP preconditioned resid norm 9.377012668452e-10 true resid norm
> 7.703045169141e-02 ||r(i)||/||b|| 1.217604347459e-01
> 418 KSP Residual norm 9.377012668452e-10 % max 1.633857814432e+02 min
> 1.541342543594e-05 max/min 1.060022524664e+07
> 419 KSP preconditioned resid norm 9.353480176536e-10 true resid norm
> 7.702931350860e-02 ||r(i)||/||b|| 1.217586356440e-01
> 419 KSP Residual norm 9.353480176536e-10 % max 1.642408586848e+02 min
> 1.541300403949e-05 max/min 1.065599271005e+07
> 420 KSP preconditioned resid norm 9.330123970972e-10 true resid norm
> 7.702818836330e-02 ||r(i)||/||b|| 1.217568571502e-01
> 420 KSP Residual norm 9.330123970972e-10 % max 1.650959375804e+02 min
> 1.541258686504e-05 max/min 1.071176039597e+07
> 421 KSP preconditioned resid norm 9.306941861701e-10 true resid norm
> 7.702707604016e-02 ||r(i)||/||b|| 1.217550989241e-01
> 421 KSP Residual norm 9.306941861701e-10 % max 1.659510181008e+02 min
> 1.541217384870e-05 max/min 1.076752830132e+07
> 422 KSP preconditioned resid norm 9.283931696573e-10 true resid norm
> 7.702597632846e-02 ||r(i)||/||b|| 1.217533606326e-01
> 422 KSP Residual norm 9.283931696573e-10 % max 1.668061002175e+02 min
> 1.541176492885e-05 max/min 1.082329642241e+07
> 423 KSP preconditioned resid norm 9.261091360496e-10 true resid norm
> 7.702488900721e-02 ||r(i)||/||b|| 1.217516419265e-01
> 423 KSP Residual norm 9.261091360496e-10 % max 1.676611839026e+02 min
> 1.541136004679e-05 max/min 1.087906475442e+07
> 424 KSP preconditioned resid norm 9.238418774628e-10 true resid norm
> 7.702381387948e-02 ||r(i)||/||b|| 1.217499424945e-01
> 424 KSP Residual norm 9.238418774628e-10 % max 1.685162691291e+02 min
> 1.541095914290e-05 max/min 1.093483329406e+07
> 425 KSP preconditioned resid norm 9.215911895577e-10 true resid norm
> 7.702275074538e-02 ||r(i)||/||b|| 1.217482620205e-01
> 425 KSP Residual norm 9.215911895577e-10 % max 1.693713558704e+02 min
> 1.541056215850e-05 max/min 1.099060203829e+07
> 426 KSP preconditioned resid norm 9.193568714629e-10 true resid norm
> 7.702169940327e-02 ||r(i)||/||b|| 1.217466001858e-01
> 426 KSP Residual norm 9.193568714629e-10 % max 1.702264441005e+02 min
> 1.541016903696e-05 max/min 1.104637098349e+07
> 427 KSP preconditioned resid norm 9.171387256997e-10 true resid norm
> 7.702065966772e-02 ||r(i)||/||b|| 1.217449566974e-01
> 427 KSP Residual norm 9.171387256997e-10 % max 1.710815337941e+02 min
> 1.540977971745e-05 max/min 1.110214012991e+07
> 428 KSP preconditioned resid norm 9.149365581086e-10 true resid norm
> 7.701963134449e-02 ||r(i)||/||b|| 1.217433312483e-01
> 428 KSP Residual norm 9.149365581086e-10 % max 1.719366249265e+02 min
> 1.540939414902e-05 max/min 1.115790947157e+07
> 429 KSP preconditioned resid norm 9.127501777777e-10 true resid norm
> 7.701861425445e-02 ||r(i)||/||b|| 1.217417235552e-01
> 429 KSP Residual norm 9.127501777777e-10 % max 1.727917174733e+02 min
> 1.540901228158e-05 max/min 1.121367900263e+07
> 430 KSP preconditioned resid norm 9.105793969736e-10 true resid norm
> 7.701760821750e-02 ||r(i)||/||b|| 1.217401333335e-01
> 430 KSP Residual norm 9.105793969736e-10 % max 1.736468114109e+02 min
> 1.540863405594e-05 max/min 1.126944872468e+07
> 431 KSP preconditioned resid norm 9.084240310736e-10 true resid norm
> 7.701661305348e-02 ||r(i)||/||b|| 1.217385602984e-01
> 431 KSP Residual norm 9.084240310736e-10 % max 1.745019067161e+02 min
> 1.540825942103e-05 max/min 1.132521863423e+07
> 432 KSP preconditioned resid norm 9.062838984992e-10 true resid norm
> 7.701562859033e-02 ||r(i)||/||b|| 1.217370041779e-01
> 432 KSP Residual norm 9.062838984992e-10 % max 1.753570033662e+02 min
> 1.540788832843e-05 max/min 1.138098872658e+07
> 433 KSP preconditioned resid norm 9.041588206529e-10 true resid norm
> 7.701465466315e-02 ||r(i)||/||b|| 1.217354647115e-01
> 433 KSP Residual norm 9.041588206529e-10 % max 1.762121013392e+02 min
> 1.540752072662e-05 max/min 1.143675900009e+07
> 434 KSP preconditioned resid norm 9.020486218545e-10 true resid norm
> 7.701369109927e-02 ||r(i)||/||b|| 1.217339416261e-01
> 434 KSP Residual norm 9.020486218545e-10 % max 1.770672006133e+02 min
> 1.540715656775e-05 max/min 1.149252945115e+07
> 435 KSP preconditioned resid norm 8.999531292809e-10 true resid norm
> 7.701273774708e-02 ||r(i)||/||b|| 1.217324346821e-01
> 435 KSP Residual norm 8.999531292809e-10 % max 1.779223011674e+02 min
> 1.540679580267e-05 max/min 1.154830007785e+07
> 436 KSP preconditioned resid norm 8.978721729060e-10 true resid norm
> 7.701179443778e-02 ||r(i)||/||b|| 1.217309436126e-01
> 436 KSP Residual norm 8.978721729060e-10 % max 1.787774029806e+02 min
> 1.540643838466e-05 max/min 1.160407087718e+07
> 437 KSP preconditioned resid norm 8.958055854435e-10 true resid norm
> 7.701086102012e-02 ||r(i)||/||b|| 1.217294681788e-01
> 437 KSP Residual norm 8.958055854435e-10 % max 1.796325060327e+02 min
> 1.540608426227e-05 max/min 1.165984185044e+07
> 438 KSP preconditioned resid norm 8.937532022898e-10 true resid norm
> 7.700993734290e-02 ||r(i)||/||b|| 1.217280081414e-01
> 438 KSP Residual norm 8.937532022898e-10 % max 1.804876103037e+02 min
> 1.540573340057e-05 max/min 1.171561298711e+07
> 439 KSP preconditioned resid norm 8.917148614689e-10 true resid norm
> 7.700902325376e-02 ||r(i)||/||b|| 1.217265632596e-01
> 439 KSP Residual norm 8.917148614689e-10 % max 1.813427157743e+02 min
> 1.540538574951e-05 max/min 1.177138428877e+07
> 440 KSP preconditioned resid norm 8.896904035794e-10 true resid norm
> 7.700811860899e-02 ||r(i)||/||b|| 1.217251333064e-01
> 440 KSP Residual norm 8.896904035794e-10 % max 1.821978224254e+02 min
> 1.540504126229e-05 max/min 1.182715575526e+07
> 441 KSP preconditioned resid norm 8.876796717414e-10 true resid norm
> 7.700722326477e-02 ||r(i)||/||b|| 1.217237180544e-01
> 441 KSP Residual norm 8.876796717414e-10 % max 1.830529302383e+02 min
> 1.540469989749e-05 max/min 1.188292738297e+07
> 442 KSP preconditioned resid norm 8.856825115457e-10 true resid norm
> 7.700633707629e-02 ||r(i)||/||b|| 1.217223172747e-01
> 442 KSP Residual norm 8.856825115457e-10 % max 1.839080391948e+02 min
> 1.540436161576e-05 max/min 1.193869916730e+07
> 443 KSP preconditioned resid norm 8.836987710040e-10 true resid norm
> 7.700545991462e-02 ||r(i)||/||b|| 1.217209307635e-01
> 443 KSP Residual norm 8.836987710040e-10 % max 1.847631492771e+02 min
> 1.540402637418e-05 max/min 1.199447110703e+07
> 444 KSP preconditioned resid norm 8.817283005006e-10 true resid norm
> 7.700459163848e-02 ||r(i)||/||b|| 1.217195582974e-01
> 444 KSP Residual norm 8.817283005006e-10 % max 1.856182604675e+02 min
> 1.540369412984e-05 max/min 1.205024320159e+07
> 445 KSP preconditioned resid norm 8.797709527445e-10 true resid norm
> 7.700373211375e-02 ||r(i)||/||b|| 1.217181996645e-01
> 445 KSP Residual norm 8.797709527445e-10 % max 1.864733727491e+02 min
> 1.540336484553e-05 max/min 1.210601544657e+07
> 446 KSP preconditioned resid norm 8.778265827233e-10 true resid norm
> 7.700288121255e-02 ||r(i)||/||b|| 1.217168546627e-01
> 446 KSP Residual norm 8.778265827233e-10 % max 1.873284861049e+02 min
> 1.540303848040e-05 max/min 1.216178784097e+07
> 447 KSP preconditioned resid norm 8.758950476583e-10 true resid norm
> 7.700203881086e-02 ||r(i)||/||b|| 1.217155230958e-01
> 447 KSP Residual norm 8.758950476583e-10 % max 1.881836005185e+02 min
> 1.540271499238e-05 max/min 1.221756038540e+07
> 448 KSP preconditioned resid norm 8.739762069604e-10 true resid norm
> 7.700120478187e-02 ||r(i)||/||b|| 1.217142047635e-01
> 448 KSP Residual norm 8.739762069604e-10 % max 1.890387159738e+02 min
> 1.540239435002e-05 max/min 1.227333307263e+07
> 449 KSP preconditioned resid norm 8.720699221868e-10 true resid norm
> 7.700037900278e-02 ||r(i)||/||b|| 1.217128994717e-01
> 449 KSP Residual norm 8.720699221868e-10 % max 1.898938324550e+02 min
> 1.540207651332e-05 max/min 1.232910590276e+07
> 450 KSP preconditioned resid norm 8.701760569996e-10 true resid norm
> 7.699956135165e-02 ||r(i)||/||b|| 1.217116070275e-01
> 450 KSP Residual norm 8.701760569996e-10 % max 1.907489499467e+02 min
> 1.540176144765e-05 max/min 1.238487887214e+07
> 451 KSP preconditioned resid norm 8.682944771243e-10 true resid norm
> 7.699875171161e-02 ||r(i)||/||b|| 1.217103272463e-01
> 451 KSP Residual norm 8.682944771243e-10 % max 1.916040684336e+02 min
> 1.540144910772e-05 max/min 1.244065198628e+07
> 452 KSP preconditioned resid norm 8.664250503101e-10 true resid norm
> 7.699794997108e-02 ||r(i)||/||b|| 1.217090599517e-01
> 452 KSP Residual norm 8.664250503101e-10 % max 1.924591879009e+02 min
> 1.540113947663e-05 max/min 1.249642522834e+07
> 453 KSP preconditioned resid norm 8.645676462907e-10 true resid norm
> 7.699715601200e-02 ||r(i)||/||b|| 1.217078049571e-01
> 453 KSP Residual norm 8.645676462907e-10 % max 1.933143083340e+02 min
> 1.540083249795e-05 max/min 1.255219861393e+07
> 454 KSP preconditioned resid norm 8.627221367466e-10 true resid norm
> 7.699636972505e-02 ||r(i)||/||b|| 1.217065620897e-01
> 454 KSP Residual norm 8.627221367466e-10 % max 1.941694297187e+02 min
> 1.540052815040e-05 max/min 1.260797213072e+07
> 455 KSP preconditioned resid norm 8.608883952670e-10 true resid norm
> 7.699559100258e-02 ||r(i)||/||b|| 1.217053311792e-01
> 455 KSP Residual norm 8.608883952670e-10 % max 1.950245520408e+02 min
> 1.540022639631e-05 max/min 1.266374578023e+07
> 456 KSP preconditioned resid norm 8.590662973146e-10 true resid norm
> 7.699481973160e-02 ||r(i)||/||b|| 1.217041120472e-01
> 456 KSP Residual norm 8.590662973146e-10 % max 1.958796752868e+02 min
> 1.539992720743e-05 max/min 1.271951955670e+07
> 457 KSP preconditioned resid norm 8.572557201889e-10 true resid norm
> 7.699405581233e-02 ||r(i)||/||b|| 1.217029045359e-01
> 457 KSP Residual norm 8.572557201889e-10 % max 1.967347994430e+02 min
> 1.539963054120e-05 max/min 1.277529346672e+07
> 458 KSP preconditioned resid norm 8.554565429923e-10 true resid norm
> 7.699329914254e-02 ||r(i)||/||b|| 1.217017084837e-01
> 458 KSP Residual norm 8.554565429923e-10 % max 1.975899244964e+02 min
> 1.539933638367e-05 max/min 1.283106749365e+07
> 459 KSP preconditioned resid norm 8.536686465960e-10 true resid norm
> 7.699254961914e-02 ||r(i)||/||b|| 1.217005237276e-01
> 459 KSP Residual norm 8.536686465960e-10 % max 1.984450504338e+02 min
> 1.539904468019e-05 max/min 1.288684165512e+07
> 460 KSP preconditioned resid norm 8.518919136065e-10 true resid norm
> 7.699180714235e-02 ||r(i)||/||b|| 1.216993501100e-01
> 460 KSP Residual norm 8.518919136065e-10 % max 1.993001772428e+02 min
> 1.539875541750e-05 max/min 1.294261593481e+07
> 461 KSP preconditioned resid norm 8.501262283338e-10 true resid norm
> 7.699107161430e-02 ||r(i)||/||b|| 1.216981874761e-01
> 461 KSP Residual norm 8.501262283338e-10 % max 2.001553049106e+02 min
> 1.539846855934e-05 max/min 1.299839033598e+07
> 462 KSP preconditioned resid norm 8.483714767594e-10 true resid norm
> 7.699034293767e-02 ||r(i)||/||b|| 1.216970356721e-01
> 462 KSP Residual norm 8.483714767594e-10 % max 2.010104334253e+02 min
> 1.539818407370e-05 max/min 1.305416485887e+07
> 463 KSP preconditioned resid norm 8.466275465054e-10 true resid norm
> 7.698962102339e-02 ||r(i)||/||b|| 1.216958945572e-01
> 463 KSP Residual norm 8.466275465054e-10 % max 2.018655627746e+02 min
> 1.539790193476e-05 max/min 1.310993949889e+07
> 464 KSP preconditioned resid norm 8.448943268044e-10 true resid norm
> 7.698890577352e-02 ||r(i)||/||b|| 1.216947639765e-01
> 464 KSP Residual norm 8.448943268044e-10 % max 2.027206929469e+02 min
> 1.539762211089e-05 max/min 1.316571425685e+07
> 465 KSP preconditioned resid norm 8.431717084698e-10 true resid norm
> 7.698819709932e-02 ||r(i)||/||b|| 1.216936437900e-01
> 465 KSP Residual norm 8.431717084698e-10 % max 2.035758239306e+02 min
> 1.539734457892e-05 max/min 1.322148912673e+07
> 466 KSP preconditioned resid norm 8.414595838671e-10 true resid norm
> 7.698749491585e-02 ||r(i)||/||b|| 1.216925338631e-01
> 466 KSP Residual norm 8.414595838671e-10 % max 2.044309557144e+02 min
> 1.539706930707e-05 max/min 1.327726411029e+07
> 467 KSP preconditioned resid norm 8.397578468854e-10 true resid norm
> 7.698679913097e-02 ||r(i)||/||b|| 1.216914340504e-01
> 467 KSP Residual norm 8.397578468854e-10 % max 2.052860882871e+02 min
> 1.539679626817e-05 max/min 1.333303920580e+07
> 468 KSP preconditioned resid norm 8.380663929100e-10 true resid norm
> 7.698610965659e-02 ||r(i)||/||b|| 1.216903442126e-01
> 468 KSP Residual norm 8.380663929100e-10 % max 2.061412216378e+02 min
> 1.539652542826e-05 max/min 1.338881441779e+07
> 469 KSP preconditioned resid norm 8.363851187952e-10 true resid norm
> 7.698542641515e-02 ||r(i)||/||b|| 1.216892642271e-01
> 469 KSP Residual norm 8.363851187952e-10 % max 2.069963557558e+02 min
> 1.539625677349e-05 max/min 1.344458973379e+07
> 470 KSP preconditioned resid norm 8.347139228382e-10 true resid norm
> 7.698474931774e-02 ||r(i)||/||b|| 1.216881939532e-01
> 470 KSP Residual norm 8.347139228382e-10 % max 2.078514906305e+02 min
> 1.539599027325e-05 max/min 1.350036515622e+07
> 471 KSP preconditioned resid norm 8.330527047528e-10 true resid norm
> 7.698407828643e-02 ||r(i)||/||b|| 1.216871332680e-01
> 471 KSP Residual norm 8.330527047528e-10 % max 2.087066262516e+02 min
> 1.539572589156e-05 max/min 1.355614069266e+07
> 472 KSP preconditioned resid norm 8.314013656445e-10 true resid norm
> 7.698341323890e-02 ||r(i)||/||b|| 1.216860820412e-01
> 472 KSP Residual norm 8.314013656445e-10 % max 2.095617626089e+02 min
> 1.539546361499e-05 max/min 1.361191633131e+07
> 473 KSP preconditioned resid norm 8.297598079857e-10 true resid norm
> 7.698275409694e-02 ||r(i)||/||b|| 1.216850401492e-01
> 473 KSP Residual norm 8.297598079857e-10 % max 2.104168996925e+02 min
> 1.539520341682e-05 max/min 1.366769207237e+07
> 474 KSP preconditioned resid norm 8.281279355912e-10 true resid norm
> 7.698210078561e-02 ||r(i)||/||b|| 1.216840074735e-01
> 474 KSP Residual norm 8.281279355912e-10 % max 2.112720374926e+02 min
> 1.539494527436e-05 max/min 1.372346791285e+07
> 475 KSP preconditioned resid norm 8.265056535949e-10 true resid norm
> 7.698145322348e-02 ||r(i)||/||b|| 1.216829838855e-01
> 475 KSP Residual norm 8.265056535949e-10 % max 2.121271759996e+02 min
> 1.539468915743e-05 max/min 1.377924385679e+07
> 476 KSP preconditioned resid norm 8.248928684267e-10 true resid norm
> 7.698081134149e-02 ||r(i)||/||b|| 1.216819692760e-01
> 476 KSP Residual norm 8.248928684267e-10 % max 2.129823152040e+02 min
> 1.539443504456e-05 max/min 1.383501990087e+07
> 477 KSP preconditioned resid norm 8.232894877893e-10 true resid norm
> 7.698017506308e-02 ||r(i)||/||b|| 1.216809635239e-01
> 477 KSP Residual norm 8.232894877893e-10 % max 2.138374550966e+02 min
> 1.539418291104e-05 max/min 1.389079604499e+07
> 478 KSP preconditioned resid norm 8.216954206367e-10 true resid norm
> 7.697954431722e-02 ||r(i)||/||b|| 1.216799665171e-01
> 478 KSP Residual norm 8.216954206367e-10 % max 2.146925956681e+02 min
> 1.539393273158e-05 max/min 1.394657228998e+07
> 479 KSP preconditioned resid norm 8.201105771517e-10 true resid norm
> 7.697891903432e-02 ||r(i)||/||b|| 1.216789781454e-01
> 479 KSP Residual norm 8.201105771517e-10 % max 2.155477369098e+02 min
> 1.539368449054e-05 max/min 1.400234862825e+07
> 480 KSP preconditioned resid norm 8.185348687256e-10 true resid norm
> 7.697829914078e-02 ||r(i)||/||b|| 1.216779982925e-01
> 480 KSP Residual norm 8.185348687256e-10 % max 2.164028788127e+02 min
> 1.539343816240e-05 max/min 1.405812506145e+07
> 481 KSP preconditioned resid norm 8.169682079365e-10 true resid norm
> 7.697768457143e-02 ||r(i)||/||b|| 1.216770268555e-01
> 481 KSP Residual norm 8.169682079365e-10 % max 2.172580213682e+02 min
> 1.539319372853e-05 max/min 1.411390158532e+07
> 482 KSP preconditioned resid norm 8.154105085294e-10 true resid norm
> 7.697707525626e-02 ||r(i)||/||b|| 1.216760637237e-01
> 482 KSP Residual norm 8.154105085294e-10 % max 2.181131645679e+02 min
> 1.539295116083e-05 max/min 1.416967820458e+07
> 483 KSP preconditioned resid norm 8.138616853962e-10 true resid norm
> 7.697647113181e-02 ||r(i)||/||b|| 1.216751087967e-01
> 483 KSP Residual norm 8.138616853962e-10 % max 2.189683084033e+02 min
> 1.539271043853e-05 max/min 1.422545491762e+07
> 484 KSP preconditioned resid norm 8.123216545560e-10 true resid norm
> 7.697587213190e-02 ||r(i)||/||b|| 1.216741619700e-01
> 484 KSP Residual norm 8.123216545560e-10 % max 2.198234528663e+02 min
> 1.539247154007e-05 max/min 1.428123172384e+07
> 485 KSP preconditioned resid norm 8.107903331364e-10 true resid norm
> 7.697527818843e-02 ||r(i)||/||b|| 1.216732231359e-01
> 485 KSP Residual norm 8.107903331364e-10 % max 2.206785979488e+02 min
> 1.539223445599e-05 max/min 1.433700861170e+07
> 486 KSP preconditioned resid norm 8.092676393541e-10 true resid norm
> 7.697468924499e-02 ||r(i)||/||b|| 1.216722922052e-01
> 486 KSP Residual norm 8.092676393541e-10 % max 2.215337436429e+02 min
> 1.539199915274e-05 max/min 1.439278559234e+07
> 487 KSP preconditioned resid norm 8.077534924970e-10 true resid norm
> 7.697410523157e-02 ||r(i)||/||b|| 1.216713690674e-01
> 487 KSP Residual norm 8.077534924970e-10 % max 2.223888899408e+02 min
> 1.539176560838e-05 max/min 1.444856266650e+07
> 488 KSP preconditioned resid norm 8.062478129065e-10 true resid norm
> 7.697352609817e-02 ||r(i)||/||b|| 1.216704536432e-01
> 488 KSP Residual norm 8.062478129065e-10 % max 2.232440368347e+02 min
> 1.539153381927e-05 max/min 1.450433981799e+07
> 489 KSP preconditioned resid norm 8.047505219590e-10 true resid norm
> 7.697295177444e-02 ||r(i)||/||b|| 1.216695458216e-01
> 489 KSP Residual norm 8.047505219590e-10 % max 2.240991843173e+02 min
> 1.539130375307e-05 max/min 1.456011705783e+07
> 490 KSP preconditioned resid norm 8.032615420497e-10 true resid norm
> 7.697238220643e-02 ||r(i)||/||b|| 1.216686455173e-01
> 490 KSP Residual norm 8.032615420497e-10 % max 2.249543323810e+02 min
> 1.539107539327e-05 max/min 1.461589438249e+07
> 491 KSP preconditioned resid norm 8.017807965749e-10 true resid norm
> 7.697181733368e-02 ||r(i)||/||b|| 1.216677526347e-01
> 491 KSP Residual norm 8.017807965749e-10 % max 2.258094810186e+02 min
> 1.539084872474e-05 max/min 1.467167178737e+07
> 492 KSP preconditioned resid norm 8.003082099158e-10 true resid norm
> 7.697125710155e-02 ||r(i)||/||b|| 1.216668670874e-01
> 492 KSP Residual norm 8.003082099158e-10 % max 2.266646302229e+02 min
> 1.539062371415e-05 max/min 1.472744928554e+07
> 493 KSP preconditioned resid norm 7.988437074224e-10 true resid norm
> 7.697070145112e-02 ||r(i)||/||b|| 1.216659887823e-01
> 493 KSP Residual norm 7.988437074224e-10 % max 2.275197799868e+02 min
> 1.539040036644e-05 max/min 1.478322685373e+07
> 494 KSP preconditioned resid norm 7.973872153972e-10 true resid norm
> 7.697015032934e-02 ||r(i)||/||b|| 1.216651176356e-01
> 494 KSP Residual norm 7.973872153972e-10 % max 2.283749303036e+02 min
> 1.539017865071e-05 max/min 1.483900450324e+07
> 495 KSP preconditioned resid norm 7.959386610801e-10 true resid norm
> 7.696960368018e-02 ||r(i)||/||b|| 1.216642535586e-01
> 495 KSP Residual norm 7.959386610801e-10 % max 2.292300811662e+02 min
> 1.538995854689e-05 max/min 1.489478223530e+07
> 496 KSP preconditioned resid norm 7.944979726328e-10 true resid norm
> 7.696906145072e-02 ||r(i)||/||b|| 1.216633964678e-01
> 496 KSP Residual norm 7.944979726328e-10 % max 2.300852325680e+02 min
> 1.538974004078e-05 max/min 1.495056004574e+07
> 497 KSP preconditioned resid norm 7.930650791238e-10 true resid norm
> 7.696852358851e-02 ||r(i)||/||b|| 1.216625462801e-01
> 497 KSP Residual norm 7.930650791238e-10 % max 2.309403845025e+02 min
> 1.538952311570e-05 max/min 1.500633793304e+07
> 498 KSP preconditioned resid norm 7.916399105142e-10 true resid norm
> 7.696799004048e-02 ||r(i)||/||b|| 1.216617029118e-01
> 498 KSP Residual norm 7.916399105142e-10 % max 2.317955369631e+02 min
> 1.538930774757e-05 max/min 1.506211590315e+07
> 499 KSP preconditioned resid norm 7.902223976426e-10 true resid norm
> 7.696746075603e-02 ||r(i)||/||b|| 1.216608662829e-01
> 499 KSP Residual norm 7.902223976426e-10 % max 2.326506899435e+02 min
> 1.538909393078e-05 max/min 1.511789394424e+07
> 500 KSP preconditioned resid norm 7.888124722116e-10 true resid norm
> 7.696693568410e-02 ||r(i)||/||b|| 1.216600363126e-01
> 500 KSP Residual norm 7.888124722116e-10 % max 2.335058434373e+02 min
> 1.538888164219e-05 max/min 1.517367206185e+07
> Linear solve did not converge due to DIVERGED_ITS iterations 500
> KSP Object: 4 MPI processes
>   type: gmres
>     restart=500, using Classical (unmodified) Gram-Schmidt
> Orthogonalization with no iterative refinement
>     happy breakdown tolerance 1e-30
>   maximum iterations=500, initial guess is zero
>   tolerances:  relative=1e-08, absolute=1e-50, divergence=10000.
>   left preconditioning
>   using PRECONDITIONED norm type for convergence test
> PC Object: 4 MPI processes
>   type: jacobi
>   linear system matrix = precond matrix:
>   Mat Object: 4 MPI processes
>     type: mpiaij
>     rows=14924, cols=14924
>     total: nonzeros=1393670, allocated nonzeros=1393670
>     total number of mallocs used during MatSetValues calls =0
>       not using I-node (on process 0) routines
> Krylov solver did not converge in 500 iters; Petsc reason: DIVERGED_ITS,
> with residual norm 7.88812e-10-------------------
> -------------------------------------------------------
> mpirun has exited due to process rank 0 with PID 14460 on
> node rook exiting improperly. There are three reasons this could occur:
>
> 1. this process did not call "init" before exiting, but others in
> the job did. This can cause a job to hang indefinitely while it waits
> for all processes to call "init". By rule, if one process calls "init",
> then ALL processes must call "init" prior to termination.
>
> 2. this process called "init", but exited without calling "finalize".
> By rule, all processes that call "init" MUST call "finalize" prior to
> exiting or it will be considered an "abnormal termination"
>
> 3. this process called "MPI_Abort" or "orte_abort" and the mca parameter
> orte_create_session_dirs is set to false. In this case, the run-time cannot
> detect that the abort call was an abnormal termination. Hence, the only
> error message you will receive is this one.
>
> This may have caused other processes in the application to be
> terminated by signals sent by mpirun (as reported here).
>
> You can avoid this message by specifying -quiet on the mpirun command line.
>
> --------------------------------------------------------------------------
>
>
>
> On 2018-05-18 10:58, Matthew Knepley wrote:
>
>> On Fri, May 18, 2018 at 5:54 AM, Y. Shidi <ys453 at cam.ac.uk> wrote:
>>
>> Hello all,
>>>
>>> I do not have much knowledge on linear iterative solvers,
>>> so when use PETSc krylov solvers, I try several combinations
>>> (e.g. cg+jacobi, gmres+hypre, etc). But I cannot get a
>>> converged solution. I have used 'preonly' and 'lu' check
>>> that the system is correctly constructed.
>>>
>>> Below is the ksp log output with 500 iterations.
>>>
>>
>> This is only 411 iterations, and we cannot see what solver was used.
>>
>> In general, the iterative solver is very sensitive to the system. We
>> recommend
>> starting with a solver that has worked before for someone by checking
>> the literature.
>>
>>   Thanks,
>>
>>      Matt
>>
>>
>>
>>
>
> --
>>
>> What most experimenters take for granted before they begin their
>> experiments is infinitely more interesting than any results to which
>> their experiments lead.
>> -- Norbert Wiener
>>
>> https://www.cse.buffalo.edu/~knepley/ [1]
>>
>>
>> Links:
>> ------
>> [1] http://www.caam.rice.edu/~mk51/
>>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
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