From 1e62bbf8c9d64f87966be7ac1a81bb30dd6ab21e Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Thu, 20 Oct 2016 00:21:06 +0200
Subject: [PATCH] Avoid adding top of environment to cache.

* mes.c (assq_ref_cache): Only consider caching symbols deeper than
  4*CACHE_SIZE depth.  50% speedup.
---
 mes.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mes.c b/mes.c
index 95787bcd..2d32c6c3 100644
--- a/mes.c
+++ b/mes.c
@@ -370,9 +370,10 @@ assq_ref_cache (scm *x, scm *a)
   x->value++;
   scm *c = cache_lookup (x);
   if (c != &scm_undefined) return c;
-  while (a != &scm_nil && x != a->car->car) a = a->cdr;
+  int i = 0;
+  while (a != &scm_nil && x != a->car->car) {i++;a = a->cdr;}
   if (a == &scm_nil) return &scm_undefined;
-  cache_save (a->car);
+  if (i>4*CACHE_SIZE) cache_save (a->car);
   return a->car->cdr;
 }
 #endif // ENV_CACHE