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https://issues.apache.org/jira/browse/MATH-1597?focusedWorklogId=621297&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-621297
]
ASF GitHub Bot logged work on MATH-1597:
----------------------------------------
Author: ASF GitHub Bot
Created on: 10/Jul/21 15:39
Start Date: 10/Jul/21 15:39
Worklog Time Spent: 10m
Work Description: amarlearning commented on a change in pull request #190:
URL: https://github.com/apache/commons-math/pull/190#discussion_r667349474
##########
File path:
commons-math-legacy/src/main/java/org/apache/commons/math4/legacy/quasirandom/HaltonSequenceGenerator.java
##########
@@ -151,31 +159,44 @@ public HaltonSequenceGenerator(final int dimension, final
int[] bases, final int
* @param digit the j-th digit
* @return the scrambled digit
*/
- protected int scramble(final int i, final int j, final int b, final int
digit) {
+ protected long scramble(final int i, final int j, final int b, final long
digit) {
return weight != null ? (weight[i] * digit) % b : digit;
}
/**
- * Skip to the i-th point in the Halton sequence.
+ * jump to the i-th point in the Halton sequence.
* <p>
* This operation can be performed in O(1).
*
* @param index the index in the sequence to skip to
- * @return the i-th point in the Halton sequence
- * @throws org.apache.commons.math4.legacy.exception.NotPositiveException
NotPositiveException if index < 0
+ * @return the copy of this sequence
+ * @throws NotPositiveException if index < 0
*/
- public double[] skipTo(final int index) {
+ @Override
+ public LowDiscrepancySequence jump(final long index) throws
NotPositiveException {
+ if(index < 0) {
+ throw new NotPositiveException(index);
+ }
+ HaltonSequenceGenerator copy = this.copy();
+ copy.performJump(index);
+ return copy;
+ }
+
+ /**
+ * Do jump at the index.
+ * @param index
+ */
+ private void performJump(long index) {
count = index;
- return get();
}
/**
- * Returns the index i of the next point in the Halton sequence that will
be returned
- * by calling {@link #get()}.
- *
- * @return the index of the next point
+ * Private constructor avoid side effects.
+ * @return copy of HaltonSequenceGenerator
*/
- public int getNextIndex() {
- return count;
+ private HaltonSequenceGenerator copy() {
+ return new HaltonSequenceGenerator(this);
}
+
+
Review comment:
extra line
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Issue Time Tracking
-------------------
Worklog Id: (was: 621297)
Time Spent: 2.5h (was: 2h 20m)
> Low-discrepancy sequence
> ------------------------
>
> Key: MATH-1597
> URL: https://issues.apache.org/jira/browse/MATH-1597
> Project: Commons Math
> Issue Type: Sub-task
> Reporter: Gilles Sadowski
> Priority: Minor
> Fix For: 4.0
>
> Time Spent: 2.5h
> Remaining Estimate: 0h
>
> Two low-discrepancy sequences are implemented in Commons Math (in package
> {{o.a.c.math4.legacy.random}}:
> * {{SobolSequenceGenerator}}
> * {{HaltonSequenceGenerator}}
> They both provide several methods:
> * {{nextVector()}}
> * {{skipTo(int)}}
> * {{getNextIndex()}}
> of which only the first is part of their common API through the
> {{RandomVectorGenerator}}.
> I propose to create an interface that would better represent the specific
> concept (and avoid the confusion with pseudo-random generators):
> {code}
> public interface LowDiscrepancySequence extends Supplier<double[]> { /* ...
> */}
> {code}
> Thus, instead of class {{SobolSequenceGenerator}} we'd have:
> {code}
> public class SobolSequence implements LowDiscrepancySequence {
> // ...
> }
> {code}
> This functionality could be moved to a new {{o.a.c.m.legacy.quasirandom}}
> package (?).
> Method {{skipTo}} could be replaced with an API similar to Commons RNG
> {{JumpableUniformRandomProvider}} (?).
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