From: Markus Armbruster <armbru@pond.sub.org>
Date: Mon, 21 Feb 2011 21:22:54 +0000 (+0100)
Subject: Exploit fast "multiple paths from same source" in distribution
X-Git-Tag: v4.3.27~94
X-Git-Url: http://git.pond.sub.org/?p=empserver;a=commitdiff_plain;h=bf97fa9c9c822cf007c13f2bc0f2ef8f4dd2d634

Exploit fast "multiple paths from same source" in distribution

Dijkstra's algorithm can find multiple paths from the same source.
This is much faster than starting from scratch for every path.

Make distribution path assembly work that way.  This speeds up runs of
distributions to the same center.  The next commit will reorder path
searches to maximize the length of these runs.  It also has benchmark
results.

Allocates four bytes per sector, actually uses only the first 4*n
bytes, where n is the number of distributing sectors.
---

diff --git a/src/lib/update/finish.c b/src/lib/update/finish.c
index c502ae649..c8d85dbae 100644
--- a/src/lib/update/finish.c
+++ b/src/lib/update/finish.c
@@ -116,6 +116,7 @@ assemble_dist_paths(double *import_cost)
     struct sctstr *sp;
     struct sctstr *dist;
     int n;
+    coord dx = 1, dy = 0;	/* invalid */
 
     for (n = 0; NULL != (sp = getsectid(n)); n++) {
 	import_cost[n] = -1;
@@ -126,9 +127,12 @@ assemble_dist_paths(double *import_cost)
 	    continue;
 	if (sp->sct_own != dist->sct_own)
 	    continue;
-	import_cost[n] = path_find(sp->sct_dist_x, sp->sct_dist_y,
-				   sp->sct_x, sp->sct_y,
-				   dist->sct_own, MOB_MOVE);
+	if (sp->sct_dist_x != dx || sp->sct_dist_y != dy) {
+	    dx = sp->sct_dist_x;
+	    dy = sp->sct_dist_y;
+	    path_find_from(dx, dy, dist->sct_own, MOB_MOVE);
+	}
+	import_cost[n] = path_find_to(sp->sct_x, sp->sct_y);
     }
     path_find_print_stats();
 }