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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/204190">204190</a></dd>
<dt>Author</dt> <dd>rniwa@webkit.org</dd>
<dt>Date</dt> <dd>2016-08-05 13:22:52 -0700 (Fri, 05 Aug 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>segmentTimeSeriesByMaximizingSchwarzCriterion returns a bogus result on empty charts
https://bugs.webkit.org/show_bug.cgi?id=160575
Rubber-stamped by Chris Dumez.
The bug was caused by an early return in segmentTimeSeriesByMaximizingSchwarzCriterion.
Removed this early return as the one in splitIntoSegmentsUntilGoodEnough was sufficient.
Also factored out a few functions in findOptimalSegmentation so that they can be better
optimized in JSC's DFG and FTL tiers, and removed unused debuggingTestingRangeNomination.
* public/shared/statistics.js:
(Statistics.segmentTimeSeriesByMaximizingSchwarzCriterion): Removed an early return.
(Statistics.splitIntoSegmentsUntilGoodEnough):
(.allocateCostUpperTriangularForSegmentation): Extracted from findOptimalSegmentation.
(.allocatePreviousNodeForSegmentation): Ditto.
(.findOptimalSegmentationInternal): Ditto.
(.findOptimalSegmentation):
* unit-tests/statistics-tests.js: Added a test case.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkWebsitesperfwebkitorgChangeLog">trunk/Websites/perf.webkit.org/ChangeLog</a></li>
<li><a href="#trunkWebsitesperfwebkitorgpublicsharedstatisticsjs">trunk/Websites/perf.webkit.org/public/shared/statistics.js</a></li>
<li><a href="#trunkWebsitesperfwebkitorgunittestsstatisticstestsjs">trunk/Websites/perf.webkit.org/unit-tests/statistics-tests.js</a></li>
</ul>
</div>
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<h3>Diff</h3>
<a id="trunkWebsitesperfwebkitorgChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Websites/perf.webkit.org/ChangeLog (204189 => 204190)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Websites/perf.webkit.org/ChangeLog 2016-08-05 20:21:35 UTC (rev 204189)
+++ trunk/Websites/perf.webkit.org/ChangeLog 2016-08-05 20:22:52 UTC (rev 204190)
</span><span class="lines">@@ -1,5 +1,28 @@
</span><span class="cx"> 2016-08-05 Ryosuke Niwa <rniwa@webkit.org>
</span><span class="cx">
</span><ins>+ segmentTimeSeriesByMaximizingSchwarzCriterion returns a bogus result on empty charts
+ https://bugs.webkit.org/show_bug.cgi?id=160575
+
+ Rubber-stamped by Chris Dumez.
+
+ The bug was caused by an early return in segmentTimeSeriesByMaximizingSchwarzCriterion.
+ Removed this early return as the one in splitIntoSegmentsUntilGoodEnough was sufficient.
+
+ Also factored out a few functions in findOptimalSegmentation so that they can be better
+ optimized in JSC's DFG and FTL tiers, and removed unused debuggingTestingRangeNomination.
+
+ * public/shared/statistics.js:
+ (Statistics.segmentTimeSeriesByMaximizingSchwarzCriterion): Removed an early return.
+ (Statistics.splitIntoSegmentsUntilGoodEnough):
+ (.allocateCostUpperTriangularForSegmentation): Extracted from findOptimalSegmentation.
+ (.allocatePreviousNodeForSegmentation): Ditto.
+ (.findOptimalSegmentationInternal): Ditto.
+ (.findOptimalSegmentation):
+
+ * unit-tests/statistics-tests.js: Added a test case.
+
+2016-08-05 Ryosuke Niwa <rniwa@webkit.org>
+
</ins><span class="cx"> Perf dashboard sometimes tries to fetch a non-existent measurement-set JSON
</span><span class="cx"> https://bugs.webkit.org/show_bug.cgi?id=160577
</span><span class="cx">
</span></span></pre></div>
<a id="trunkWebsitesperfwebkitorgpublicsharedstatisticsjs"></a>
<div class="modfile"><h4>Modified: trunk/Websites/perf.webkit.org/public/shared/statistics.js (204189 => 204190)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Websites/perf.webkit.org/public/shared/statistics.js 2016-08-05 20:21:35 UTC (rev 204189)
+++ trunk/Websites/perf.webkit.org/public/shared/statistics.js 2016-08-05 20:22:52 UTC (rev 204190)
</span><span class="lines">@@ -174,9 +174,6 @@
</span><span class="cx">
</span><span class="cx"> this.debuggingSegmentation = false;
</span><span class="cx"> this.segmentTimeSeriesByMaximizingSchwarzCriterion = function (values) {
</span><del>- if (values.length < 2)
- return [0];
-
</del><span class="cx"> // Split the time series into grids since splitIntoSegmentsUntilGoodEnough is O(n^2).
</span><span class="cx"> var gridLength = 500;
</span><span class="cx"> var totalSegmentation = [0];
</span><span class="lines">@@ -308,17 +305,26 @@
</span><span class="cx"> return segmentation;
</span><span class="cx"> }
</span><span class="cx">
</span><del>- function findOptimalSegmentation(values, costMatrix, segmentCount) {
</del><ins>+ function allocateCostUpperTriangularForSegmentation(values, segmentCount)
+ {
</ins><span class="cx"> // Dynamic programming. cost[i][k] = The cost to segmenting values up to i into k segments.
</span><span class="cx"> var cost = new Array(values.length);
</span><span class="cx"> for (var segmentEnd = 0; segmentEnd < values.length; segmentEnd++)
</span><span class="cx"> cost[segmentEnd] = new Float32Array(segmentCount + 1);
</span><ins>+ return cost;
+ }
</ins><span class="cx">
</span><ins>+ function allocatePreviousNodeForSegmentation(values, segmentCount)
+ {
</ins><span class="cx"> // previousNode[i][k] = The start of the last segment in an optimal segmentation that ends at i with k segments.
</span><span class="cx"> var previousNode = new Array(values.length);
</span><span class="cx"> for (var i = 0; i < values.length; i++)
</span><span class="cx"> previousNode[i] = new Array(segmentCount + 1);
</span><ins>+ return previousNode;
+ }
</ins><span class="cx">
</span><ins>+ function findOptimalSegmentationInternal(cost, previousNode, values, costMatrix, segmentCount)
+ {
</ins><span class="cx"> cost[0] = [0]; // The cost of segmenting single value is always 0.
</span><span class="cx"> previousNode[0] = [-1];
</span><span class="cx"> for (var segmentStart = 0; segmentStart < values.length; segmentStart++) {
</span><span class="lines">@@ -338,7 +344,14 @@
</span><span class="cx"> }
</span><span class="cx"> }
</span><span class="cx"> }
</span><ins>+ }
</ins><span class="cx">
</span><ins>+ function findOptimalSegmentation(values, costMatrix, segmentCount) {
+ var cost = allocateCostUpperTriangularForSegmentation(values, segmentCount);
+ var previousNode = allocatePreviousNodeForSegmentation(values, segmentCount);
+
+ findOptimalSegmentationInternal(cost, previousNode, values, costMatrix, segmentCount);
+
</ins><span class="cx"> if (Statistics.debuggingSegmentation) {
</span><span class="cx"> console.log('findOptimalSegmentation with', segmentCount, 'segments');
</span><span class="cx"> for (var end = 0; end < values.length; end++) {
</span><span class="lines">@@ -393,8 +406,6 @@
</span><span class="cx"> return this.costMatrix[from][to - from - 1];
</span><span class="cx"> }
</span><span class="cx">
</span><del>- this.debuggingTestingRangeNomination = false;
-
</del><span class="cx"> })();
</span><span class="cx">
</span><span class="cx"> if (typeof module != 'undefined')
</span></span></pre></div>
<a id="trunkWebsitesperfwebkitorgunittestsstatisticstestsjs"></a>
<div class="modfile"><h4>Modified: trunk/Websites/perf.webkit.org/unit-tests/statistics-tests.js (204189 => 204190)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Websites/perf.webkit.org/unit-tests/statistics-tests.js 2016-08-05 20:21:35 UTC (rev 204189)
+++ trunk/Websites/perf.webkit.org/unit-tests/statistics-tests.js 2016-08-05 20:22:52 UTC (rev 204190)
</span><span class="lines">@@ -355,6 +355,11 @@
</span><span class="cx"> });
</span><span class="cx">
</span><span class="cx"> describe('segmentTimeSeriesByMaximizingSchwarzCriterion', function () {
</span><ins>+ it('should segment time series of length 0 into a single segment', function () {
+ var values = [];
+ assert.deepEqual(Statistics.segmentTimeSeriesByMaximizingSchwarzCriterion(values), [0, 0]);
+ });
+
</ins><span class="cx"> it('should not segment time series of length two into two pieces', function () {
</span><span class="cx"> var values = [1, 2];
</span><span class="cx"> assert.deepEqual(Statistics.segmentTimeSeriesByMaximizingSchwarzCriterion(values), [0, 2]);
</span></span></pre>
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