From fc96e12a0a71e954b005167751aa442a87f28779 Mon Sep 17 00:00:00 2001
From: Damien Elmes <git@ichi2.net>
Date: Tue, 29 Mar 2011 09:44:08 +0900
Subject: [PATCH] add some randomness to lrn interval

---
 anki/sched.py       | 6 +++++-
 tests/test_sched.py | 3 ++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/anki/sched.py b/anki/sched.py
index 545ad8295..0f5b582aa 100644
--- a/anki/sched.py
+++ b/anki/sched.py
@@ -294,7 +294,11 @@ limit %d""" % self.reportLimit, lim=self.dayCutoff)
                 card.grade += 1
             else:
                 card.grade = 0
-            card.due = time.time() + self._delayForGrade(conf, card.grade)
+            delay = self._delayForGrade(conf, card.grade)
+            if card.due < time.time():
+                # not collapsed; add some randomness
+                delay *= random.uniform(1, 1.25)
+            card.due = time.time() + delay
             heappush(self.lrnQueue, (card.due, card.id))
         self._logLrn(card, ease, conf, leaving, type)
 
diff --git a/tests/test_sched.py b/tests/test_sched.py
index 95eee323d..0e87128db 100644
--- a/tests/test_sched.py
+++ b/tests/test_sched.py
@@ -65,7 +65,8 @@ def test_learn():
     # fail it
     d.sched.answerCard(c, 1)
     # it should by due in 30 seconds
-    assert round(c.due - time.time()) == 30
+    t = round(c.due - time.time())
+    assert t >= 30 and t <= 40
     # and have 1 cycle, but still a zero grade
     assert c.grade == 0
     assert c.cycles == 1