Hello Matthew, I was indeed wondering if there was a clean way to match a given set of options to a specific KSP instance. Does the following makes sense:
1. Associate a given a KSP instance a unique string, e.g. “toto” and call ksp_1.setOptionsPrefix(“toto”) 2. Create an option database with corresponding prefix: options = Options(“toto_ksp_”) 3. Then a call to ksp_1.setFromOptions() will only consider entrees in the option database starting with “toto” Regards, Alexandre. De : Matthew Knepley <[email protected]> Envoyé : lundi 27 octobre 2025 11:27 À : SCOTTO Alexandre <[email protected]> Cc : [email protected] Objet : Re: [petsc-users] Options database in petsc4py On Mon, Oct 27, 2025 at 10:24 AM SCOTTO Alexandre via petsc-users <[email protected]<mailto:[email protected]>> wrote: Dear PETSc Community, In my developments, I am managing possibly several KSP solvers with options handled by the Options database. During my tests, I encountered the following behavior: Code: options = PETSc.Options("ksp_") options.setValue("atol", 7e-8) options.view() options.clear() options.view() Output: #PETSc Option Table entries: -ksp_atol 7e-08 # (source: code) #End of PETSc Option Table entries #PETSc Option Table entries: -ksp_atol 7e-08 # (source: code) #End of PETSc Option Table entries It seems that the clear() method does not really clear the Option database. To ensure that the several KSP I deal with are set with their own options (without getting options from a KSP previously set), the only way I found was to explicitly call the delValue() method for all the option keys passed: 1. Iterate over a dictionary of options and use setValue(name, value) 2. Set the KSP with option database: KSP.setFromOptions() 3. Iterate over a the keys of the dictionary and use delValue(name) to effectively clear the option database. Does it seem normal to you, is there something I am missing out? That for pointing out this bug. However, I don't think I would manage options this way. We normally give each separate solver a new _prefix_, meaning a string that prefaces all its options. That way they do not collide. Thanks, Matt Regards, Alexandre Scotto. -- 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://urldefense.us/v3/__https://www.cse.buffalo.edu/*knepley/__;fg!!G_uCfscf7eWS!ZnPxnrdflWTbGbGUEH1FqwWm8qDvjVXbO9Vcz0i-G4kvOUAXnvdAeosPUQrtGbXE74bfCgrSlkSnKeAt0Pd0lPTS4gzeowrsYHOBb_MjQw$ <https://urldefense.us/v3/__http://www.cse.buffalo.edu/*knepley/__;fg!!G_uCfscf7eWS!ZnPxnrdflWTbGbGUEH1FqwWm8qDvjVXbO9Vcz0i-G4kvOUAXnvdAeosPUQrtGbXE74bfCgrSlkSnKeAt0Pd0lPTS4gzeowrsYHPXgj5rjg$ >
