GridInterp_Scalar3D_t Subroutine

  subroutine GridInterp_Scalar3D_t(this,f)
    implicit none
    class(Scalar3D_t),intent(in) :: this
    real(prec),intent(out) :: f(1:this%M+1,1:this%M+1,1:this%M+1,1:this%nelem,1:this%nvar)
    !! (Output) Array of function values, defined on the target grid
    ! Local
    integer :: i,j,k,ii,jj,kk,iel,ivar
    real(prec) :: fi,fij,fijk

    do concurrent(i=1:this%M+1,j=1:this%M+1, &
                  k=1:this%M+1,iel=1:this%nelem,ivar=1:this%nvar)

      fijk = 0.0_prec
      do kk = 1,this%N+1
        fij = 0.0_prec
        do jj = 1,this%N+1
          fi = 0.0_prec
          do ii = 1,this%N+1
            fi = fi+this%interior(ii,jj,kk,iel,ivar)*this%interp%iMatrix(ii,i)
          enddo
          fij = fij+fi*this%interp%iMatrix(jj,j)
        enddo
        fijk = fijk+fij*this%interp%iMatrix(kk,k)
      enddo
      f(i,j,k,iel,ivar) = fijk

    enddo

  endsubroutine GridInterp_Scalar3D_t