CEP3

Status	Active
Author	Kyle Mandli <kyle.mandli@gmail.com>
Created	Nov. 5, 2014
Updated	March 19, 2015
Discussion	Riemann #92
Implementation

Motivation

Sometimes Riemann solvers need more information than is currently available inside the routine without resorting to common blocks or module variables which inevitably are not thread safe.

Specification

The proposed solution to this problem is to create a void * like interface that would let arbitrary data be passed to the Riemann solver. rp_data would be defined in each Riemann solver module and would utilized the iso_c_binding module to accomplish the generic data type.

An example Riemann solver module using an rp_data type would be defined as follows:

module rp1_advection
    
    implicit none

    type rp_type
        real(kind=8) :: u
    end type rp_type

contains

subroutine rp1_ptwise(num_eqn, num_waves, rp_data, q_l, q_r, aux_l, aux_r, wave, s, amdq, apdq)

    use iso_c_binding, only: c_ptr

    implicit none

    ...
    type(c_ptr), intent(in out) :: rp_data
    ...

    ! Local type
    type(rp_type), pointer :: rp_aux

    call c_f_pointer(rp_data, rp_aux)

    ...
end subroutine rp1_ptwise

end module rp1_advection

Backwards Compatibility Issues

This will clearly break backwards compatibility as the calling sequence will drastically change.

Notes

• See also the long discussion: https://groups.google.com/forum/?hl=en#!topic/claw-dev/7G67NxwzxsE.
• This proposal depends on accepting and implementing #89 first.
• This proposal is similar to #88.