[petsc-dev] simplification of solvers that utilize KSPNASH STCG or GLTR

[Barry Smith]

> On Aug 21, 2016, at 11:33 PM, Munson, Todd <tmunson at mcs.anl.gov> wrote:
> 
> 
> I don't see any reason not to make the change.

   I any new solvers are to be added in the future that utilize the KSPCGXXX solver functionality they would be easier and cleaner to implement.

   Barry

> 
> Todd.
> 
>> On Aug 21, 2016, at 9:40 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>> 
>> 
>>  Todd,
>> 
>>   The TAO solvers that utilize KSPNASH STCG or GLTR have all this horribly redundant unneeded code 
>> 
>>     /* Solve the trust region subproblem */
>>     if (NTR_KSP_NASH == tr->ksp_type) {
>>       ierr = KSPNASHSetRadius(tao->ksp,tao->trust);CHKERRQ(ierr);
>>       ierr = KSPSolve(tao->ksp, tao->gradient, tao->stepdirection);CHKERRQ(ierr);
>>       ierr = KSPGetIterationNumber(tao->ksp,&its);CHKERRQ(ierr);
>>       tao->ksp_its+=its;
>>       tao->ksp_tot_its+=its;
>>       ierr = KSPNASHGetNormD(tao->ksp, &norm_d);CHKERRQ(ierr);
>>     } else if (NTR_KSP_STCG == tr->ksp_type) {
>>       ierr = KSPSTCGSetRadius(tao->ksp,tao->trust);CHKERRQ(ierr);
>>       ierr = KSPSolve(tao->ksp, tao->gradient, tao->stepdirection);CHKERRQ(ierr);
>>       ierr = KSPGetIterationNumber(tao->ksp,&its);CHKERRQ(ierr);
>>       tao->ksp_its+=its;
>>       tao->ksp_tot_its+=its;
>>       ierr = KSPSTCGGetNormD(tao->ksp, &norm_d);CHKERRQ(ierr);
>>     } else { /* NTR_KSP_GLTR */
>>       ierr = KSPGLTRSetRadius(tao->ksp,tao->trust);CHKERRQ(ierr);
>>       ierr = KSPSolve(tao->ksp, tao->gradient, tao->stepdirection);CHKERRQ(ierr);
>>       ierr = KSPGetIterationNumber(tao->ksp,&its);CHKERRQ(ierr);
>>       tao->ksp_its+=its;
>>       tao->ksp_tot_its+=its;
>>       ierr = KSPGLTRGetNormD(tao->ksp, &norm_d);CHKERRQ(ierr);
>>     }
>> 
>> This can be simplified a great deal by making the names 
>> 
>> KSPCGSetRadius(), KSPGGGetNormD() etc you only need to change the registration from 
>> 
>> ierr = PetscObjectComposeFunction((PetscObject)ksp,"KSPNASHSetRadius_C",KSPNASHSetRadius_NASH);CHKERRQ(ierr);
>> ierr = PetscObjectComposeFunction((PetscObject)ksp,"KSPNASHGetNormD_C",KSPNASHGetNormD_NASH);CHKERRQ(ierr);
>> ierr = PetscObjectComposeFunction((PetscObject)ksp,"KSPNASHGetObjFcn_C",KSPNASHGetObjFcn_NASH);CHKERRQ(ierr);
>> 
>> to 
>> 
>> 
>> ierr = PetscObjectComposeFunction((PetscObject)ksp,"KSPCGSetRadius_C",KSPCGSetRadius_NASH);CHKERRQ(ierr);
>> ierr = PetscObjectComposeFunction((PetscObject)ksp,"KSPCGGetNormD_C",KSPCGGetNormD_NASH);CHKERRQ(ierr);
>> ierr = PetscObjectComposeFunction((PetscObject)ksp,"KSPCGGetObjFcn_C",KSPCGGetObjFcn_NASH);CHKERRQ(ierr);
>> 
>> Is there any reason we shouldn't do this? Essentially these three KSPs are a special subclass of KSPCG that supports these additional methods.  Anything specific to an individual one like the Lanczo stuff still remains with it.
>> 
>> Barry
>> 
>> 
>> 
>> 
>