svn commit: r1488969 - in /commons/proper/math/trunk/src: main/java/org/apache/commons/math3/analysis/integration/MidPointIntegrator.java test/java/org/apache/commons/math3/analysis/integration/MidPointIntegratorTest.java

[luc]

Author: luc
Date: Mon Jun  3 12:10:36 2013
New Revision: 1488969

URL: http://svn.apache.org/r1488969
Log:
Fixed wrong first iteration for midpoint integrator.

Thanks to Gilles for spotting the issue.

Modified:
    
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/analysis/integration/MidPointIntegrator.java
    
commons/proper/math/trunk/src/test/java/org/apache/commons/math3/analysis/integration/MidPointIntegratorTest.java

Modified: 
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/analysis/integration/MidPointIntegrator.java
URL: 
http://svn.apache.org/viewvc/commons/proper/math/trunk/src/main/java/org/apache/commons/math3/analysis/integration/MidPointIntegrator.java?rev=1488969&r1=1488968&r2=1488969&view=diff
==============================================================================
--- 
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/analysis/integration/MidPointIntegrator.java
 (original)
+++ 
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/analysis/integration/MidPointIntegrator.java
 Mon Jun  3 12:10:36 2013
@@ -120,7 +120,7 @@ public class MidPointIntegrator extends 
         final double diff = getMax() - min;
 
         if (n == 0) {
-            final double midPoint = 0.5 * diff;
+            final double midPoint = min + 0.5 * diff;
             return diff * computeObjectiveValue(midPoint);
         } else {
             final long np = 1L << (n - 1);           // number of new points 
in this stage

Modified: 
commons/proper/math/trunk/src/test/java/org/apache/commons/math3/analysis/integration/MidPointIntegratorTest.java
URL: 
http://svn.apache.org/viewvc/commons/proper/math/trunk/src/test/java/org/apache/commons/math3/analysis/integration/MidPointIntegratorTest.java?rev=1488969&r1=1488968&r2=1488969&view=diff
==============================================================================
--- 
commons/proper/math/trunk/src/test/java/org/apache/commons/math3/analysis/integration/MidPointIntegratorTest.java
 (original)
+++ 
commons/proper/math/trunk/src/test/java/org/apache/commons/math3/analysis/integration/MidPointIntegratorTest.java
 Mon Jun  3 12:10:36 2013
@@ -39,6 +39,25 @@ public final class MidPointIntegratorTes
      * Test of integrator for the sine function.
      */
     @Test
+    public void testLowAccuracy() {
+        UnivariateFunction f = new QuinticFunction();
+        UnivariateIntegrator integrator = new MidPointIntegrator(0.01, 
1.0e-10, 2, 4);
+        
+        double min = -10;
+        double max =  -9;
+        double expected = -3697001.0 / 48.0;
+        double tolerance = FastMath.abs(expected * 
integrator.getRelativeAccuracy());
+        double result = integrator.integrate(Integer.MAX_VALUE, f, min, max);
+        Assert.assertTrue(integrator.getEvaluations() < Integer.MAX_VALUE / 2);
+        Assert.assertTrue(integrator.getIterations() < 
MidPointIntegrator.MIDPOINT_MAX_ITERATIONS_COUNT / 2);
+        Assert.assertEquals(expected, result, tolerance);
+
+    }
+
+    /**
+     * Test of integrator for the sine function.
+     */
+    @Test
     public void testSinFunction() {
         UnivariateFunction f = new Sin();
         UnivariateIntegrator integrator = new MidPointIntegrator();