Blacklist hashes for 2d integer elements

The hash table for integer hashes is extremely limited and places most
elements in the same buckets.  This leads to a linear search time for
structures built on this.

This blocks hashes, directing the coder to utilize std::set or std::map
structures instead of hash tables for implementing integer-based
lookups.

common/view/view_group.cpp

@@ -112,7 +112,7 @@ void VIEW_GROUP::ViewDraw( int aLayer, VIEW* aView ) const
 
     const std::vector<VIEW_ITEM*> drawList = updateDrawList();
 
-    std::unordered_map<int, std::vector<VIEW_ITEM*>> layer_item_map;
+    std::map<int, std::vector<VIEW_ITEM*>> layer_item_map;
 
     // Build a list of layers used by the items in the group
     for( VIEW_ITEM* item : drawList )
@@ -123,13 +123,6 @@ void VIEW_GROUP::ViewDraw( int aLayer, VIEW* aView ) const
         for( int i = 0; i < item_layers_count; i++ )
         {
             wxCHECK2_MSG( item_layers[i] <= LAYER_ID_COUNT, continue, wxT( "Invalid item layer" ) );
-
-            if( layer_item_map.count( item_layers[i] ) == 0 )
-            {
-                layer_item_map.emplace( std::make_pair( item_layers[i],
-                                                        std::vector<VIEW_ITEM*>() ) );
-            }
-
             layer_item_map[ item_layers[i] ].push_back( item );
         }
     }

common/wx_stl_compat.cpp

@@ -29,16 +29,6 @@ size_t std::hash<wxString>::operator()( const wxString& s ) const
 #endif
 
 #ifdef USE_KICAD_WXPOINT_LESS_AND_HASH
-size_t std::hash<wxPoint>::operator() ( const wxPoint& k ) const
-{
-    auto xhash = std::hash<int>()( k.x );
-
-    // 0x9e3779b9 is 2^33 / ( 1 + sqrt(5) )
-    // Adding this value ensures that consecutive bits of y will not be close to each other
-    // decreasing the likelihood of hash collision in similar values of x and y
-    return xhash ^ ( std::hash<int>()( k.y )  + 0x9e3779b9 + ( xhash << 6 ) + ( xhash >> 2 ) );
-}
-
 bool std::less<wxPoint>::operator()( const wxPoint& aA, const wxPoint& aB ) const
 {
     if( aA.x == aB.x )

eeschema/erc.cpp

@@ -411,7 +411,7 @@ int ERC_TESTER::TestNoConnectPins()
 
     for( const SCH_SHEET_PATH& sheet : m_schematic->GetSheets() )
     {
-        std::unordered_map<VECTOR2I, std::vector<SCH_PIN*>> pinMap;
+        std::map<VECTOR2I, std::vector<SCH_PIN*>> pinMap;
 
         for( SCH_ITEM* item : sheet.LastScreen()->Items().OfType( SCH_SYMBOL_T ) )
         {
@@ -863,4 +863,4 @@ int ERC_TESTER::TestOffGridEndpoints( int aGridSize )
     }
 
     return err_count;
-}
+}

include/core/wx_stl_compat.h

@@ -43,7 +43,7 @@ namespace std
 {
     template <> struct hash<wxPoint>
     {
-        size_t operator() ( const wxPoint& k ) const;
+        size_t operator() ( const wxPoint& k ) const = delete;
     };
 }
 

libs/kimath/include/math/vector2d.h

@@ -611,13 +611,17 @@ typedef VECTOR2<unsigned int> VECTOR2U;
 namespace std
 {
     // Required to enable correct use in std::map/unordered_map
+    // DO NOT USE hash tables with VECTOR2 elements.  It is inefficient
+    // and degenerates to a linear search.  Use the std::map/std::set
+    // trees instead that utilize the less operator below
+    // This function is purposely deleted after substantial testing
     template <>
     struct hash<VECTOR2I>
     {
-        size_t operator()( const VECTOR2I& k ) const;
+        size_t operator()( const VECTOR2I& k ) const = delete;
     };
 
-    // Required to enable use of std::hash with maps
+    // Required to enable use of std::hash with maps.
     template <>
     struct less<VECTOR2I>
     {

libs/kimath/src/math/vector2.cpp

@@ -19,22 +19,10 @@
 
 #include <math/vector2d.h>
 
-
-size_t std::hash<VECTOR2I>::operator()( const VECTOR2I& k ) const
-{
-    auto xhash = std::hash<int>()( k.x );
-
-    // 0x9e3779b9 is 2^33 / ( 1 + sqrt(5) )
-    // Adding this value ensures that consecutive bits of y will not be close to each other
-    // decreasing the likelihood of hash collision in similar values of x and y
-    return xhash ^ ( std::hash<int>()( k.y ) + 0x9e3779b9 + ( xhash << 6 ) + ( xhash >> 2 ) );
-}
-
-
 bool std::less<VECTOR2I>::operator()( const VECTOR2I& aA, const VECTOR2I& aB ) const
 {
     if( aA.x == aB.x )
         return aA.y < aB.y;
 
     return aA.x < aB.x;
-}
+}

pcbnew/drc/drc_engine.h

@@ -243,7 +243,7 @@ protected:
     bool                       m_testFootprints;
 
     // constraint -> rule -> provider
-    std::unordered_map<DRC_CONSTRAINT_T, std::vector<DRC_ENGINE_CONSTRAINT*>*> m_constraintMap;
+    std::map<DRC_CONSTRAINT_T, std::vector<DRC_ENGINE_CONSTRAINT*>*> m_constraintMap;
 
     DRC_VIOLATION_HANDLER      m_violationHandler;
     REPORTER*                  m_reporter;

pcbnew/drc/drc_test_provider_copper_clearance.cpp

@@ -854,7 +854,7 @@ void DRC_TEST_PROVIDER_COPPER_CLEARANCE::testZonesToZones()
                 }
 
                 // Iterate through all the segments of refSmoothedPoly
-                std::unordered_map<VECTOR2I, int> conflictPoints;
+                std::map<VECTOR2I, int> conflictPoints;
 
                 for( auto refIt = smoothed_polys[ia].IterateSegmentsWithHoles(); refIt; refIt++ )
                 {

pcbnew/tools/pcb_selection_tool.cpp

@@ -1140,12 +1140,12 @@ void PCB_SELECTION_TOOL::selectAllConnectedTracks(
 
     auto connectivity = board()->GetConnectivity();
 
-    std::unordered_map<VECTOR2I, std::vector<PCB_TRACK*>> trackMap;
-    std::unordered_map<VECTOR2I, PCB_VIA*>                viaMap;
-    std::unordered_map<VECTOR2I, PAD*>                    padMap;
-    std::set<PAD*>                                        startPadSet;
-    std::vector<BOARD_CONNECTED_ITEM*>                    cleanupItems;
-    std::vector<std::pair<VECTOR2I, LSET>>                activePts;
+    std::map<VECTOR2I, std::vector<PCB_TRACK*>> trackMap;
+    std::map<VECTOR2I, PCB_VIA*>                viaMap;
+    std::map<VECTOR2I, PAD*>                    padMap;
+    std::set<PAD*>                              startPadSet;
+    std::vector<BOARD_CONNECTED_ITEM*>          cleanupItems;
+    std::vector<std::pair<VECTOR2I, LSET>>      activePts;
 
     for( BOARD_CONNECTED_ITEM* startItem : aStartItems )
     {