Iteration 0011 — 8c29b124a2c6 (accepted)

GitHub commit: 8c29b124a2c6 Published branch: fermilink-optimize/lammps-neighbor

Change summary

Use contiguous _noalias aliases for hot coordinate/type/tag/molecule arrays in the incumbent NPairBin<1,1,0,0,0>::build() path

Acceptance rationale

Correctness held and the candidate cut weighted_median_neigh_seconds from 0.31969 to 0.31150 (-2.56% vs incumbent), clearing the 2.0% promotion gate.

Guardrails & metrics

field	value
decision	ACCEPTED
correctness	ok
correctness mode	field_tolerances
hard reject	no
guardrail errors	0
incumbent commit	c4128d3970b2
candidate commit	8c29b124a2c6
incumbent metric	0.31969
candidate metric	0.3115
baseline metric	0.36158
Δ vs incumbent	+2.562% (lower-is-better sign)
changed files	src/npair_bin.cpp

Diffstat

src/npair_bin.cpp | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)

Diff

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diff --git a/src/npair_bin.cpp b/src/npair_bin.cpp
index 42917b2dda..178d975ed0 100644
--- a/src/npair_bin.cpp
+++ b/src/npair_bin.cpp
@@ -46,13 +46,15 @@ void NPairBin<1, 1, 0, 0, 0>::build(NeighList *list)
   int *neighptr;
   double xtmp, ytmp, ztmp, delx, dely, delz, rsq;

-  double **x = atom->x;
-  int *type = atom->type;
-  int *mask = atom->mask;
-  tagint *tag = atom->tag;
-  tagint *molecule = atom->molecule;
-  tagint **special = atom->special;
-  int **nspecial = atom->nspecial;
+  using dbl3_t = double[3];
+
+  const auto * _noalias const x = (const dbl3_t *) atom->x[0];
+  const int * _noalias const type = atom->type;
+  int * _noalias const mask = atom->mask;
+  const tagint * _noalias const tag = atom->tag;
+  tagint * _noalias const molecule = atom->molecule;
+  tagint * const * _noalias const special = atom->special;
+  int * const * _noalias const nspecial = atom->nspecial;
   int nlocal = atom->nlocal;
   if (includegroup) nlocal = atom->nfirst;

@@ -78,7 +80,7 @@ void NPairBin<1, 1, 0, 0, 0>::build(NeighList *list)
       neighptr = ipage->vget();

       itype = type[i];
-      const double *const cutneighsq_i = cutneighsq[itype];
+      const double * _noalias const cutneighsq_i = cutneighsq[itype];
       const tagint molecule_i = molecule[i];
       const tagint *const special_i = special[i];
       const int *const nspecial_i = nspecial[i];