compare wcs extent using significant digits

qgis · Sep 27, 2012 · a49975a · sdikiy · Sep 27, 2012 · a49975a
1 parent 4d93a92
commit a49975a
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Showing 3 changed files with 28 additions and 9 deletions.
diff --git a/src/core/qgis.h b/src/core/qgis.h
@@ -154,6 +154,24 @@ inline bool doubleNear( double a, double b, double epsilon = 4 * DBL_EPSILON )
   return diff > -epsilon && diff <= epsilon;
 }
 
+//
+// compare two doubles using specified number of significant digits
+//
+inline bool doubleNearSig( double a, double b, int significantDigits = 10 )
+{
+  // The most simple would be to print numbers as %.xe and compare as strings
+  // but that is probably too costly
+  // Then the fastest would be to set some bits directly, but little/big endian
+  // has to be considered (maybe TODO)
+  // Is there a better way?
+  int aexp, bexp;
+  double ar = frexp( a, &aexp );
+  double br = frexp( b, &bexp );
+
+  return aexp == bexp &&
+         round( ar * pow( 10, significantDigits ) ) == round( br * pow( 10, significantDigits ) ) ;
+}
+
 /** Wkt string that represents a geographic coord sys
  * @note added in 1.8 to replace GEOWkt
  */

diff --git a/src/providers/wcs/qgswcsprovider.cpp b/src/providers/wcs/qgswcsprovider.cpp
@@ -534,10 +534,12 @@ void QgsWcsProvider::readBlock( int bandNo, QgsRectangle  const & viewExtent, in
     QgsRectangle cacheExtent = QgsGdalProviderBase::extent( mCachedGdalDataset );
     QgsDebugMsg( "viewExtent = " + viewExtent.toString() );
     QgsDebugMsg( "cacheExtent = " + cacheExtent.toString() );
-    if ( !doubleNear( cacheExtent.xMinimum(), viewExtent.xMinimum() ) ||
-         !doubleNear( cacheExtent.yMinimum(), viewExtent.yMinimum() ) ||
-         !doubleNear( cacheExtent.xMaximum(), viewExtent.xMaximum() ) ||
-         !doubleNear( cacheExtent.yMaximum(), viewExtent.yMaximum() ) )
+    // using doubleNear is too precise, example accetable difference:
+    // 179.9999999306699863 x 179.9999999306700431
+    if ( !doubleNearSig( cacheExtent.xMinimum(), viewExtent.xMinimum(), 10 ) ||
+         !doubleNearSig( cacheExtent.yMinimum(), viewExtent.yMinimum(), 10 ) ||
+         !doubleNearSig( cacheExtent.xMaximum(), viewExtent.xMaximum(), 10 ) ||
+         !doubleNearSig( cacheExtent.yMaximum(), viewExtent.yMaximum(), 10 ) )
     {
       QgsDebugMsg( "cacheExtent and viewExtent differ" );
       QgsMessageLog::logMessage( tr( "Received coverage has wrong extent %1 (expected %2)" ).arg( cacheExtent.toString() ).arg( viewExtent.toString() ), tr( "WCS" ) );
@@ -1380,10 +1382,10 @@ bool QgsWcsProvider::calculateExtent()
     QgsRectangle cacheExtent = QgsGdalProviderBase::extent( mCachedGdalDataset );
     QgsDebugMsg( "mCoverageExtent = " + mCoverageExtent.toString() );
     QgsDebugMsg( "cacheExtent = " + cacheExtent.toString() );
-    if ( !doubleNear( cacheExtent.xMinimum(), mCoverageExtent.xMinimum() ) ||
-         !doubleNear( cacheExtent.yMinimum(), mCoverageExtent.yMinimum() ) ||
-         !doubleNear( cacheExtent.xMaximum(), mCoverageExtent.xMaximum() ) ||
-         !doubleNear( cacheExtent.yMaximum(), mCoverageExtent.yMaximum() ) )
+    if ( !doubleNearSig( cacheExtent.xMinimum(), mCoverageExtent.xMinimum(), 10 ) ||
+         !doubleNearSig( cacheExtent.yMinimum(), mCoverageExtent.yMinimum(), 10 ) ||
+         !doubleNearSig( cacheExtent.xMaximum(), mCoverageExtent.xMaximum(), 10 ) ||
+         !doubleNearSig( cacheExtent.yMaximum(), mCoverageExtent.yMaximum(), 10 ) )
     {
       QgsDebugMsg( "cacheExtent and mCoverageExtent differ, mCoverageExtent cut to cacheExtent" );
       mCoverageExtent = cacheExtent;

diff --git a/tests/src/providers/testqgswcspublicservers.cpp b/tests/src/providers/testqgswcspublicservers.cpp
@@ -779,7 +779,6 @@ void TestQgsWcsPublicServers::report()
   myRep += ".errmsg { color: #ff0000; }";
   myRep += "</style>";
 
-  myRep += QString( "<p>Tested first %1 coverages for each server/version</p>" ).arg( mMaxCoverages );
   myRep += QString( "<b>Servers: %1</b><br>\n" ).arg( myServerCount );
   myRep += QString( "<b>Servers with error: %1</b><br>\n" ).arg( myServerErrCount );
   myRep += QString( "<b>Servers with warning: %1</b><br>\n" ).arg( myServerWarnCount );