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Removed branching.

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git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1488992 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Gilles Sadowski 2013-06-03 13:48:23 +00:00
parent e68422227f
commit bd445c9b14
1 changed files with 31 additions and 25 deletions
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56
src/main/java/org/apache/commons/math3/analysis/integration/MidPointIntegrator.java
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@ -105,47 +105,54 @@ public class MidPointIntegrator extends BaseAbstractUnivariateIntegrator {
* arbitrary m sections because this configuration can best utilize the
* already computed values.</p>
*
* @param n the stage of 1/2 refinement, n = 0 is no refinement
* @param previousStageResult Result from the previous call to the {@code stage}
* method. It is unused in the first stage (when {@code n} is equal to 0).
* @param n the stage of 1/2 refinement. Must be larger than 0.
* @param previousStageResult Result from the previous call to the
* {@code stage} method.
* @param min Lower bound of the integration interval.
* @param diffMaxMin Difference between the lower bound and upper bound
* of the integration interval.
* @return the value of n-th stage integral
* @throws TooManyEvaluationsException if the maximal number of evaluations
* is exceeded.
*/
private double stage(final int n,
double previousStageResult)
double previousStageResult,
double min,
double diffMaxMin)
throws TooManyEvaluationsException {
final double min = getMin();
final double diff = getMax() - min;
// number of new points in this stage
final long np = 1L << (n - 1);
double sum = 0;
if (n == 0) {
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
double sum = 0;
// spacing between adjacent new points
final double spacing = diff / np;
double x = min + 0.5 * spacing; // the first new point
for (long i = 0; i < np; i++) {
sum += computeObjectiveValue(x);
x += spacing;
}
// add the new sum to previously calculated result
return 0.5 * (previousStageResult + sum * spacing);
// spacing between adjacent new points
final double spacing = diffMaxMin / np;
// the first new point
double x = min + 0.5 * spacing;
for (long i = 0; i < np; i++) {
sum += computeObjectiveValue(x);
x += spacing;
}
// add the new sum to previously calculated result
return 0.5 * (previousStageResult + sum * spacing);
}
/** {@inheritDoc} */
protected double doIntegrate()
throws MathIllegalArgumentException, TooManyEvaluationsException, MaxCountExceededException {
double oldt = stage(0, 0d);
iterations.incrementCount();
final double min = getMin();
final double diff = getMax() - min;
final double midPoint = min + 0.5 * diff;
double oldt = diff * computeObjectiveValue(midPoint);
while (true) {
iterations.incrementCount();
final int i = iterations.getCount();
final double t = stage(i, oldt);
final double t = stage(i, oldt, min, diff);
if (i >= getMinimalIterationCount()) {
final double delta = FastMath.abs(t - oldt);
final double rLimit =
@ -155,7 +162,6 @@ public class MidPointIntegrator extends BaseAbstractUnivariateIntegrator {
}
}
oldt = t;
iterations.incrementCount();
}
}