Bug report: `src/m/mech/basalstress.m` Logic Inconsistency

[inwoo-park]

Hi developers,

According to frcition.m, md.friction.coupling is defined as

0: uniform sheet $N=\rho_i g H + \rho_w z_b g$ ($z_b$ is elevation of ice base)
1: ice pressure only $N=\rho_i H g$
2: water pressure assuming uniform sheet $N=\max(\rho_i g H + \rho_w g z_b, 0)$
3: use provided effective pressure (~ md.friction.effective_pressure)
4: use coupled model (not implemented yet).

However, src/m/mech/basalstress.m contains following logic:

switch(md.friction.coupling)
   case 0
      N = max(md.constants.g*(md.materials.rho_ice*md.geometry.thickness+md.materials.rho_water*md.geometry.base),0);
   case 3
      N = max(md.friction.effective_pressure, 0);
   otherwise
      error('not supported yet');
end

I believe the above code should be updated to

switch(md.friction.coupling)
   case 0
      N = md.constants.g*(md.materials.rho_ice*md.geometry.thickness+md.materials.rho_water*md.geometry.base);
   case 1
      N = md.constants.g*md.materials.rho_ice;
   case 2
      N = max(md.constants.g*(md.materials.rho_ice*md.geometry.thickness+md.materials.rho_water*md.geometry.base),0);
   case 3
      N = max(md.friction.effective_pressure, 0);
   case 4
      error('md.friction.coupling=4 is not supported yet.');
   otherwise
      error('not supported yet');
end

If there is agreement on this change, I will commit the updated code to the main branch.

Best regards,
Inwoo

[TidbitSoftware]

@MathieuMorlighem are you good with this?

[MathieuMorlighem]

oh yes, this is very straightforward and harmless (basalstress.m is not affecting the actual calculation of issm.exe), @inwoo-park you should create a pull request for this?
Cheers

[inwoo-park]

Hi,

I uploaded pull request: #74. After the pull request is accepted, I will close this issue.

Cheers.