[Nek5000-users] explstrs routine

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

Paul,

Ah, yes, I see it now.  Basically, you WOULD need two 1/J 's in the
computation, but yes, I was forgetting that w3m1 is just the weights
without the Jacobian added in.  So J will cancel out one of the 1/J's.

Thanks!

On Fri, Jul 29, 2011 at 10:32 PM,  <nek5000-users at lists.mcs.anl.gov> wrote:
>
> Hi Josh,
>
> You need the jacobian at least once, since normally:
>
>   B = w3m1*Jac
>
> Does this make sense?
>
> Paul
>
>
> On Fri, 29 Jul 2011, nek5000-users at lists.mcs.anl.gov wrote:
>
>> Hello Neks
>>
>> I came across the routine explstrs (and its subroutines) while
>> exploring the code (and with the recommendation from Paul).  I
>> understand that it is essentially performing something like
>>
>>  D^T * B * D * [u]
>>
>> I had a question about the use of the Jacobian in the routine
>> expl_strs_e_3d (or _2d).  Following the routine, I can see where it
>>
>> 1) Computes the gradients w.r.t. r, s, t   (gradl_rst)
>>
>> 2) Multiplies these gradients by appropriate coordinate derivatives
>> (rxm1, tzm1, etc)
>>
>> 3) Multiplies these results by the quadrature weights. (from w3m1)
>>
>> 4) Multiplies these results again by the coordinate transformations,
>> and then apply the transpose operation (gradl_rst_t)
>>
>> When I look in coef.f, I see that when dr/dx, ds/dx, etc. are computed
>> from dx/dr, dy/ds, etc., the inverse of the Jacobian is not applied
>> yet.  So, I can see why jacmi is multiplied along with w3m1 when
>> multiplying by the quadrature weights.
>>
>> My question is, would we not need to multiply again by jacmi when the
>> transpose derivative operator is applied (because of the use of rxm1,
>> sxm1, etc)?  Is this something that is applied later on, or am I
>> missing something and it isn't necessary to apply it again?
>>
>> Thank you,
>>
>> Josh
>>
>> --
>> Josh Camp
>>
>> "All that is necessary for the triumph of evil is that good men do
>> nothing" -- Edmund Burke
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-- 
Josh Camp

"All that is necessary for the triumph of evil is that good men do
nothing" -- Edmund Burke