From 3df967056bf48bd9f87900f3a1ad9af2aedce948 Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Wed, 28 Oct 2026 16:14:30 -0700
Subject: Backport some minor speedups

---
 .../seaofnodes/simple/SchedulingScratchTest.java   | 31 ++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 chapter15/src/test/java/com/seaofnodes/simple/SchedulingScratchTest.java

(limited to 'chapter15/src/test/java/com')

diff --git a/chapter15/src/test/java/com/seaofnodes/simple/SchedulingScratchTest.java b/chapter15/src/test/java/com/seaofnodes/simple/SchedulingScratchTest.java
new file mode 100644
index 00000000..b3984f15
--- /dev/null
+++ b/chapter15/src/test/java/com/seaofnodes/simple/SchedulingScratchTest.java
@@ -0,0 +1,31 @@
+package com.seaofnodes.simple;
+
+import com.seaofnodes.simple.evaluator.Evaluator;
+import com.seaofnodes.simple.node.StopNode;
+import org.junit.Test;
+import static org.junit.Assert.assertEquals;
+
+public class SchedulingScratchTest {
+    @Test public void testScratchAcrossCompilations() {
+        String src = """
+            int[] xs = new int[2];
+            xs[0] = arg;
+            int sum = 0;
+            int i = 0;
+            while( i<5 ) {
+                int old = xs[arg&1];
+                xs[0] = i;
+                sum = sum + old;
+                i = i + 1;
+            }
+            return sum;
+            """;
+        // Each fresh compilation reuses node IDs and the scheduler's scratch.
+        for( int round=0; round<3; round++ ) {
+            StopNode stop = new Parser(src).parse().iterate();
+            assertEquals(6L,Evaluator.evaluate(stop,0));
+            assertEquals(0L,Evaluator.evaluate(stop,1));
+            assertEquals(8L,Evaluator.evaluate(stop,2));
+        }
+    }
+}
-- 
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