From 6797afe3096ce9bb29057d74abb0dde68cea5ff2 Mon Sep 17 00:00:00 2001
From: James Willis <james.s.willis@durham.ac.uk>
Date: Tue, 29 May 2018 11:33:45 +0100
Subject: [PATCH] Find the root of pi in the outer loop and update it on the
fly in the inner loop. Saves having to call fof_find at every iteration of
the inner loop.
---
src/fof.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)
diff --git a/src/fof.c b/src/fof.c
index d22592cfcd..15a0012fdc 100644
--- a/src/fof.c
+++ b/src/fof.c
@@ -258,6 +258,9 @@ void fof_search_cell(struct space *s, struct cell *c, int *pid,
const double piz = pi->x[2];
const size_t offset_i = pi->offset;
+ /* Find the root of pi. */
+ int root_i = fof_find(offset_i, pid);
+
for (size_t j = i + 1; j < count; j++) {
struct gpart *pj = &gparts[j];
@@ -278,8 +281,7 @@ void fof_search_cell(struct space *s, struct cell *c, int *pid,
r2 += dx[k] * dx[k];
}
- /* Find the roots of pi and pj. */
- const int root_i = fof_find(offset_i, pid);
+ /* Find the root of pj. */
const int root_j = fof_find(offset_j, pid);
/* Skip particles in the same group. */
@@ -288,8 +290,13 @@ void fof_search_cell(struct space *s, struct cell *c, int *pid,
/* Hit or miss? */
if (r2 < l_x2) {
- if (root_j < root_i)
+ /* If the root ID of pj is lower than pi's root ID set pi's root to point to pj's.
+ * Otherwise set pj's to root to point to pi's.*/
+ if (root_j < root_i) {
pid[root_i] = root_j;
+ /* Update root_i on the fly. */
+ root_i = root_j;
+ }
else
pid[root_j] = root_i;
@@ -336,13 +343,15 @@ void fof_search_pair_cells(struct space *s, struct cell *ci, struct cell *cj,
const double piz = pi->x[2] - shift[2];
const size_t offset_i = pi->offset;
+ /* Find the root of pi. */
+ int root_i = fof_find(offset_i, pid);
+
for (size_t j = 0; j < count_j; j++) {
struct gpart *pj = &gparts_j[j];
const size_t offset_j = pj->offset;
- /* Find the roots of pi and pj. */
- const int root_i = fof_find(offset_i, pid);
+ /* Find the root of pj. */
const int root_j = fof_find(offset_j, pid);
/* Skip particles in the same group. */
@@ -364,8 +373,13 @@ void fof_search_pair_cells(struct space *s, struct cell *ci, struct cell *cj,
/* Hit or miss? */
if (r2 < l_x2) {
- if (root_j < root_i)
+ /* If the root ID of pj is lower than pi's root ID set pi's root to point to pj's.
+ * Otherwise set pj's to root to point to pi's.*/
+ if (root_j < root_i) {
pid[root_i] = root_j;
+ /* Update root_i on the fly. */
+ root_i = root_j;
+ }
else
pid[root_j] = root_i;
--
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