[geos-commits] [SCM] GEOS branch 3.9 updated. e615f6ca286cb15bad3f919e066b4b3bbd8cad58

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- Log -----------------------------------------------------------------
commit e615f6ca286cb15bad3f919e066b4b3bbd8cad58
Author: Even Rouault <even.rouault at spatialys.com>
Date:   Wed Jun 16 17:41:15 2021 +0200

    SegmentNodeList::getSplitCoordinates(): fix quadratic performance pattern
    
    getSplitCoordinates() calls addEdgeCoordinates() repeatdly, which itself
    calls std::unique() on the whole coordList, thus iterating from the
    start each time, which is a quadratic performance pattern. As
    addEdgeCoordinates() is a private method only called by
    getSplitCoordinates(), move the call to std::unique() to the end of
    getSplitCoordinates() itself.
    
    Issue was detected when observing long runtimes on safe-TestBufferJagged.xml
    
    Before this PR:
    $ /home/even/geos/build_cmake/bin/test_xmltester -v /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test1: buffer(a, 0.35): ok. (11 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test2: buffer(a, 0.75): ok. (155 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test3: buffer(a, 1.01): ok. (209 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test4: buffer(a, 1.1): ok. (210 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test5: buffer(a, 1.5): ok. (310 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test6: buffer(a, 2): ok. (429 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test7: buffer(a, 5): ok. (1326 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test8: buffer(a, 10): ok. (2497 ms)
    
    After:
    $ /home/even/geos/build_cmake/bin/test_xmltester -v /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test1: buffer(a, 0.35): ok. (11 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test2: buffer(a, 0.75): ok. (65 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test3: buffer(a, 1.01): ok. (79 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test4: buffer(a, 1.1): ok. (78 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test5: buffer(a, 1.5): ok. (105 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test6: buffer(a, 2): ok. (133 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test7: buffer(a, 5): ok. (302 ms)
    /home/even/geos/tests/xmltester/tests/misc/safe-TestBufferJagged.xml: case1: test8: buffer(a, 10): ok. (464 ms)
    Files: 1
    Tests: 8
    Failed: 0
    Succeeded: 8

diff --git a/NEWS b/NEWS
index 2fafc2c..46559bf 100644
--- a/NEWS
+++ b/NEWS
@@ -8,6 +8,7 @@ Changes in 3.9.2
   - Fix IsValidOp to correctly report invalid nested MultiPolygons (#1112, Martin Davis)
   - Fix BufferOp to avoid artifacts in certain polygon buffers (#1101, Martin Davis)
   - Declare parameterless functions in geos_c.h as func(void) (Paul Ramsey)
+  - Performance improvement in SegmentNodeList (Even Rouault)
 
 
 Changes in 3.9.1
diff --git a/src/noding/SegmentNodeList.cpp b/src/noding/SegmentNodeList.cpp
index ec5cebc..4cd5be6 100644
--- a/src/noding/SegmentNodeList.cpp
+++ b/src/noding/SegmentNodeList.cpp
@@ -301,6 +301,8 @@ SegmentNodeList::getSplitCoordinates()
         addEdgeCoordinates(eiPrev, ei, *coordList);
         eiPrev = ei;
     }
+    // Remove duplicate Coordinates from coordList
+    coordList->erase(std::unique(coordList->begin(), coordList->end()), coordList->end());
     return coordList;
 }
 
@@ -312,8 +314,6 @@ SegmentNodeList::addEdgeCoordinates(const SegmentNode* ei0, const SegmentNode* e
     createSplitEdgePts(ei0, ei1, pts);
     // Append pts to coordList
     coordList.insert(coordList.end(), pts.begin(), pts.end());
-    // Remove duplicate Coordinates from coordList
-    coordList.erase(std::unique(coordList.begin(), coordList.end()), coordList.end());
 }
 
 

-----------------------------------------------------------------------

Summary of changes:
 NEWS                           | 1 +
 src/noding/SegmentNodeList.cpp | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)


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