[Nek5000-users] weak derivative, dssum and binvm1 in cvode_driver

[nek5000-users at lists.mcs.anl.gov]

I’m adding another quick question:

why in the routine makeq, under the cvode statement, there are these following 2 lines:
             call col2(bq,bintm1,ntot)
             call col2(bq,bm1,ntot)

I’m not sure to understand why we are multiplying bq by the inverse of the mass matrix (bintm1) and just after multiplying it back by the mass matrix (bm1). Moreover, after leaving the makeq routine, fctfun will multiplying again ydot=bq/vtrans by the inverse of the mass matrix.

Why all of these operations? Thank you for your help !



Best regards,
Emmanuel



On 5 Jun 2014, at 12:14, <nek5000-users at lists.mcs.anl.gov<mailto:nek5000-users at lists.mcs.anl.gov>> <nek5000-users at lists.mcs.anl.gov<mailto:nek5000-users at lists.mcs.anl.gov>> wrote:

Dear Nek team,

I have a quick question: in cvode_driver.f, in the routine fcvfun, do all the derivatives must be in weak formulation (using wgradm1) when constructing the right hand side term ydot?
Because at the end of the routine fcvfun,  dssum and multiplication by binvm1 are applied to the right hand side term ydot.

It’s also not clear to me if I need to apply dssum and binvm1 for each derivative term appearing in my equation (in other terms, each time after calling wgradm1), or if I need to apply dssum and binvm1 only to the whole RHS term ydot ?

I’m afraid of inconsistency if apply twice dssum and binvm1: one during the construction of operators and one on the final ydot term.

Thank you for you help !

Best regards,
Emmanuel



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