[petsc-users] Question about ts_ssp

[Jed Brown]

Note that you cannot do 5 stages with rks3 because 5 is not square (such a
method would be in a different class). Use 4 or 9 stages with rks3.
On Jul 18, 2011 6:42 PM, "Sean Farley" <sean at mcs.anl.gov> wrote:
>>
>> Methods can be chosen with -ts_ssp_type {rks2,rks3,rk104}
>>
>> rks2: Second order methods with any number s>1 of stages. c_eff = (s-1)/s
>>
>> rks3: Third order methods with s=n^2 stages, n>1. c_eff = (s-n)/s
>>
>> rk104: A 10-stage fourth order method. c_eff = 0.6
>>
>
> This means that there there are only three options for -ts_ssp_type.
Namely,
>
> -ts_ssp_type rks2
> -ts_ssp_type rks3
> -ts_ssp_type rk104
>
>> However, when I write
>>
>> -ts_ssp_type rk53
>>
>
> Therefore, this is not even close to being valid. What are you trying to
do?
> Get 5 work stages? You can see other ssp options with the -h option
> (probably helps to pipe the output to 'grep'),
>
> ./program -ts_type ssp -h | grep ssp
> -ts_type <beuler>: TS method (one of) euler beuler cn pseudo gl ssp theta
> alpha
> -ts_ssp_type <rk104>: Type of SSP method (one of) rks2 rks3 rk104
> (TSSSPSetType)
> -ts_ssp_nstages <5>: Number of stages (TSSSPSetNumStages)
>
> So, you would probably want the following options,
>
> ./program -ts_type ssp -ts_ssp_type rks3 -ts_ssp_nstages 5
>
> but keep in mind that 5 is the default for -ts_ssp_nstages.
>
> Hope that helps.
>
> Sean
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