From 2db9879e1b4671c412b50a8a3c67eda1c6c95d93 Mon Sep 17 00:00:00 2001
From: Steven Knight <knight@baldmt.com>
Date: Mon, 18 Feb 2002 22:34:59 +0000
Subject: Efficiency:  On the Taskmaster's Walker's out-of-date checks, don't
 return any children if the node itself has already been visited.

---
 src/CHANGES.txt                     |  3 +++
 src/engine/SCons/Taskmaster.py      |  4 ++++
 src/engine/SCons/TaskmasterTests.py | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 40 insertions(+)

diff --git a/src/CHANGES.txt b/src/CHANGES.txt
index d3f6aa0..b364ac7 100644
--- a/src/CHANGES.txt
+++ b/src/CHANGES.txt
@@ -65,6 +65,9 @@ RELEASE 0.05 -
 
   - Add preliminary support for Unicode strings.
 
+  - Efficiency:  don't scan dependencies more than once during the
+    walk of a tree.
+
   From Anthony Roach:
 
   - Make the scons script return an error code on failures.
diff --git a/src/engine/SCons/Taskmaster.py b/src/engine/SCons/Taskmaster.py
index 558845d..cdee378 100644
--- a/src/engine/SCons/Taskmaster.py
+++ b/src/engine/SCons/Taskmaster.py
@@ -166,6 +166,10 @@ class Taskmaster:
     def __init__(self, targets=[], tasker=Task, calc=Calc()):
         
         def out_of_date(node):
+            if node.get_state():
+                # The state is set, so someone has already been here
+                # (finished or currently executing).  Find another one.
+                return []
             # Scan the file before fetching its children().
             node.scan()
             return filter(lambda x: x.get_state() != SCons.Node.up_to_date,
diff --git a/src/engine/SCons/TaskmasterTests.py b/src/engine/SCons/TaskmasterTests.py
index 0d7a7ad..32a1110 100644
--- a/src/engine/SCons/TaskmasterTests.py
+++ b/src/engine/SCons/TaskmasterTests.py
@@ -32,6 +32,7 @@ import SCons.Errors
 
 built = None
 executed = None
+scan_called = 0
 
 class Node:
     def __init__(self, name, kids = [], scans = []):
@@ -58,6 +59,8 @@ class Node:
 	return self.kids
 
     def scan(self):
+	global scan_called
+	scan_called = scan_called + 1
         self.kids = self.kids + self.scans
         for scan in self.scans:
             scan.parents.append(self)
@@ -240,6 +243,36 @@ class TaskmasterTestCase(unittest.TestCase):
         assert t.get_target() == n3
         t.executed()
         assert tm.next_task() == None
+
+	n1 = Node("n1")
+	n2 = Node("n2")
+	n3 = Node("n3", [n1, n2])
+	n4 = Node("n4", [n3])
+	n5 = Node("n5", [n3])
+	global scan_called
+	scan_called = 0
+	tm = SCons.Taskmaster.Taskmaster([n4])
+	t = tm.next_task()
+        assert t.get_target() == n1
+	t.executed()
+	t = tm.next_task()
+        assert t.get_target() == n2
+	t.executed()
+	t = tm.next_task()
+        assert t.get_target() == n3
+	t.executed()
+	t = tm.next_task()
+        assert t.get_target() == n4
+	t.executed()
+	assert tm.next_task() == None
+	assert scan_called == 4, scan_called
+
+	tm = SCons.Taskmaster.Taskmaster([n5])
+	t = tm.next_task()
+        assert t.get_target() == n5, t.get_target()
+	t.executed()
+	assert tm.next_task() == None
+	assert scan_called == 5, scan_called
     
     def test_cycle_detection(self):
         n1 = Node("n1")
-- 
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