[Nek5000-users] intp_rstd; coarse to fine and back

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

Hello,
To know more about the subroutines used for dealiasing, I perform a simple
exercise.
I take a simple sine function and project it onto the fine mesh and back to
the coarse using intp_rstd.
When I compare the values of the processed array with the original array,
it is scaled by a factor of 1.25204, ie, I get a function like
1.25204*sin(2*x)
Could you please tell me which factor am I missing? Which jacobian has to
be multiplied?
Attached is the usr file and below are the operations I perform in short.

      sinax(i,1,1,1)      = sin(2.*x)

     call intp_rstd(uf1,u1,nx1,nxd,if3d,0) ! 0 --> forward
      nxyzd = lxd*lyd*lzd
         do i=1,nxyzd
            tr1   = uf1(i)
            wf(i) = tr1*rx(i,1,e)+tr1*rx(i,2,e)+tr1*rx(i,3,e)
         enddo

      call intp_rstd(w1,wf,nx1,nxd,if3d,1) ! 1 --> back to coarse

      nxyz = lx1*ly1*lz1           !
         do i=1,nxyz               ! to physical space.
            bi = 1./((bm1(i,1,1,e)))   !
            w1(i) = bi*w1(i)
            jacm=jacmi(i,e) ! I dont know whether to use jacmi(i,e) or not
         enddo
Thank you in advance.

Sandeep
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