[gmx-developers] oddity in code - intentional?

[jan]

Hi all,
I've been diverted by some other things, plus had a lot of learning to
do. Still at it.

Anyway, trying to understand how the gromacs code works in the hot
loops. I'm looking at how kernel_ElecEwTwinCut_VdwLJCombGeom_F.cpp
gets built up.

I noticed what I'd describe as a syntactic discrepancy (which is not
to say it's wrong, just visually aberrant).

>From 2 different parts of the expansion (the # stuff is the
preprocessor line-syncing stuff. Ignore it).

--- (A) ---
    fscal_S1 = rinvsq_S1 * (frcoul_S1 + frLJ_S1);
# 1179 "kernel_inner.h"
    fscal_S2 = rinvsq_S2 * (frcoul_S2 + frLJ_S2);
    fscal_S3 = rinvsq_S3 * (frcoul_S3 + frLJ_S3);
---

--- (B) ---
    fscal_S1 = rinvsq_S1 * (frcoul_S1 + frLJ_S1);
# 1187 "kernel_inner.h"
    fscal_S2 = rinvsq_S2 * frcoul_S2;
    fscal_S3 = rinvsq_S3 * frcoul_S3;
---


The top one A all have the same form, the bottom B is mixed. Dunno if
bug, just looked odd.

Relevant piece of source code seems to be this from kernel_inner.h

---
#    ifdef CALC_LJ
#        ifdef CALC_COULOMB
    fscal_S0 = rinvsq_S0 * (frcoul_S0 + frLJ_S0);
#        else
    fscal_S0 = rinvsq_S0 * frLJ_S0;
#        endif
#        ifdef CALC_COULOMB
    fscal_S1 = rinvsq_S1 * (frcoul_S1 + frLJ_S1);
#        else
    fscal_S1 = rinvsq_S1 * frLJ_S1;
#        endif
#    else
    fscal_S0 = rinvsq_S0 * frcoul_S0;
    fscal_S1 = rinvsq_S1 * frcoul_S1;
#    endif /* CALC_LJ */
#    if defined CALC_LJ && !defined HALF_LJ
#        ifdef CALC_COULOMB
    fscal_S2 = rinvsq_S2 * (frcoul_S2 + frLJ_S2);
    fscal_S3 = rinvsq_S3 * (frcoul_S3 + frLJ_S3);
#        else
    fscal_S2 = rinvsq_S2 * frLJ_S2;
    fscal_S3 = rinvsq_S3 * frLJ_S3;
#        endif
#    else
    /* Atom 2 and 3 don't have LJ, so only add Coulomb forces */
    fscal_S2 = rinvsq_S2 * frcoul_S2;
    fscal_S3 = rinvsq_S3 * frcoul_S3;
#    endif
---

thanks

jan