Changeset 17862

Timestamp:

03/09/21 08:11:24 (3 years ago)

Author:

gkronber

Message:

#2985: merged r17797,r17796,r17820 from trunk to stable

Location:

stable

Files:

• . (modified) (1 prop)
• HeuristicLab.Problems.DataAnalysis.Symbolic (modified) (1 prop)
• HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Converters/TreeSimplifier.cs (modified) (7 diffs)
• HeuristicLab.Tests (modified) (1 prop)
• HeuristicLab.Tests/HeuristicLab.Problems.DataAnalysis.Symbolic-3.4/SymbolicDataAnalysisExpressionTreeSimplifierTest.cs (modified) (2 diffs)

stable/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Converters/TreeSimplifier.cs

@@ -933 +933 @@
         var constB = b as ConstantTreeNode;
         var constBValue = Math.Round(constB.Value);
-        if (constBValue.IsAlmost(1.0)) {
+        if (constBValue == 1.0) {
+          // root(a, 1) => a
           return a;
-        } else if (constBValue.IsAlmost(0.0)) {
-          return MakeConstant(1.0);
-        } else if (constBValue.IsAlmost(-1.0)) {
+        } else if (constBValue == 0.0) {
+          // root(a, 0) is not defined 
+          //return MakeConstant(1.0);
+          return MakeConstant(double.NaN);
+        } else if (constBValue == -1.0) {
+          // root(a, -1) => a^(-1/1) => 1/a
           return MakeFraction(MakeConstant(1.0), a);
         } else if (constBValue < 0) {
+          // root(a, -b) => a^(-1/b) => (1/a)^(1/b) => root(1, b) / root(a, b) => 1 / root(a, b)
           var rootNode = rootSymbol.CreateTreeNode();
           rootNode.AddSubtree(a);
@@ -987 +992 @@
         var constB = b as ConstantTreeNode;
         double exponent = Math.Round(constB.Value);
-        if (exponent.IsAlmost(0.0)) {
+        if (exponent == 0.0) {
+          // a^0 => 1
           return MakeConstant(1.0);
-        } else if (exponent.IsAlmost(1.0)) {
+        } else if (exponent == 1.0) {
+          // a^1 => a
           return a;
-        } else if (exponent.IsAlmost(-1.0)) {
+        } else if (exponent == -1.0) {
+          // a^-1 => 1/a
           return MakeFraction(MakeConstant(1.0), a);
         } else if (exponent < 0) {
+          // a^-b => (1/a)^b => 1/(a^b)
           var powNode = powSymbol.CreateTreeNode();
           powNode.AddSubtree(a);
@@ -1018 +1027 @@
         // fold constants
         return MakeConstant(((ConstantTreeNode)a).Value / ((ConstantTreeNode)b).Value);
-      } else if ((IsConstant(a) && !((ConstantTreeNode)a).Value.IsAlmost(1.0))) {
+      } else if ((IsConstant(a) && ((ConstantTreeNode)a).Value != 1.0)) {
+        // a / x => (a * 1/a) / (x * 1/a) => 1 / (x * 1/a)
         return MakeFraction(MakeConstant(1.0), MakeProduct(b, Invert(a)));
       } else if (IsVariableBase(a) && IsConstant(b)) {
@@ -1094 +1104 @@
         // b is not constant => make sure constant is on the right
         return MakeSum(b, a);
-      } else if (IsConstant(b) && ((ConstantTreeNode)b).Value.IsAlmost(0.0)) {
+      } else if (IsConstant(b) && ((ConstantTreeNode)b).Value == 0.0) {
         // x + 0 => x
         return a;
@@ -1210 +1220 @@
       foreach (var unchangedSubtree in unchangedSubtrees)
         sum.AddSubtree(unchangedSubtree);
-      if (!constant.IsAlmost(0.0)) {
+      if (constant != 0.0) {
         sum.AddSubtree(MakeConstant(constant));
       }
@@ -1268 +1278 @@
         if (wi < 0) throw new ArgumentException();
         return MakeBinFactor(node1.Symbol, node1.VariableName, node1.VariableValue, node1.Weight * node0.Weights[wi]);
-      } else if (IsConstant(b) && ((ConstantTreeNode)b).Value.IsAlmost(1.0)) {
+      } else if (IsConstant(b) && ((ConstantTreeNode)b).Value == 1.0) {
         // $ * 1.0 => $
         return a;
-      } else if (IsConstant(b) && ((ConstantTreeNode)b).Value.IsAlmost(0.0)) {
+      } else if (IsConstant(b) && ((ConstantTreeNode)b).Value == 0.0) {
         return MakeConstant(0);
       } else if (IsConstant(b) && IsVariableBase(a)) {
@@ -1419 +1429 @@
         prod.AddSubtree(unchangedSubtree);
 
-      if (!constantProduct.IsAlmost(1.0)) {
+      if (constantProduct != 1.0) {
         prod.AddSubtree(MakeConstant(constantProduct));
       }

stable/HeuristicLab.Tests/HeuristicLab.Problems.DataAnalysis.Symbolic-3.4/SymbolicDataAnalysisExpressionTreeSimplifierTest.cs

@@ -99 +99 @@
       #region root rules
       // cancellation
-      AssertEqualAfterSimplification("(root (variable 2.0 a) 0.0)", "1.0");
+      AssertEqualAfterSimplification("(root (variable 2.0 a) 0.0)", "NaN");
       // fixed point
       AssertEqualAfterSimplification("(root (variable 2.0 a) 1.0)", "(variable 2.0 a)");
@@ -269 +269 @@
 
       #endregion
+
+      #region do not drop subtrees with small weights
+      AssertEqualAfterSimplification("(* 1e-14 (variable 1.0 a))", "(variable 1e-14 a)");
+      AssertEqualAfterSimplification("(+ (variable 1.0 a) 1e-14)", 
+                                     "(+ (variable 1.0 a) 1e-14)");
+      // a scenario where a term with small weight can have large effect
+      AssertEqualAfterSimplification("(+ (* (pow (variable 1.0 a) 10) 1e-14) 1.0)",
+                                     "(+ (* (pow (variable 1.0 a) 10) 1e-14) 1.0)");
+      // a test case (from ticket #2985)
+      AssertEqualAfterSimplification("(+ (* (exp (variable 3.5861E+001 a)) 5.5606E-016) 5.9323E-002)",
+                                     "(+ (* (exp (variable 3.5861E+001 a)) 5.5606E-016) 5.9323E-002)");
+      #endregion
     }