CharacteristicPolynomial - improve performance

HannesWell · Jan 10, 2024 · 0911494 · 0911494
1 parent 381b437
commit 0911494
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Showing 3 changed files with 27 additions and 14 deletions.
diff --git a/...id_library/matheclipse-core/src/main/java/org/matheclipse/core/builtin/LinearAlgebra.java b/...id_library/matheclipse-core/src/main/java/org/matheclipse/core/builtin/LinearAlgebra.java
@@ -1009,8 +1009,18 @@ public static IAST generateCharacteristicPolynomial(int dim, IAST matrix, IExpr
       // new GenPolynomialRing<edu.jas.poly.Complex<BigRational>>(cf, vars);
       // GenMatrix<edu.jas.poly.Complex<BigRational>> A;
       // pf.charPolynomial(A);
-      final IExpr[] valuesForIdentityMatrix = {F.C0, variable};
-      return F.Det(F.Subtract(matrix, diagonalMatrix(valuesForIdentityMatrix, dim)));
+
+      return F.Det(subtractDiagonalValue(dim, matrix, variable));
+    }
+
+    private static IASTAppendable subtractDiagonalValue(int dimension, IAST matrix, IExpr value) {
+      IASTAppendable subtractMatrix = F.ListAlloc(dimension);
+      for (int i = 1; i < dimension + 1; i++) {
+        IASTMutable row = ((IAST) matrix.get(i)).copy();
+        row.set(i, row.get(i).subtract(value));
+        subtractMatrix.append(row);
+      }
+      return subtractMatrix;
     }
 
     @Override

diff --git a/...ary/matheclipse-core/src/test/java/org/matheclipse/core/system/LinearAlgebraTestCase.java b/...ary/matheclipse-core/src/test/java/org/matheclipse/core/system/LinearAlgebraTestCase.java
@@ -73,6 +73,19 @@ public void testAntisymmetricMatrixQ() {
         "True");
   }
 
+
+  @Test
+  public void testCharacteristicPolynomial() {
+    check("CharacteristicPolynomial({{a, b}, {c, d}}, x)", //
+        "-b*c+a*d-a*x-d*x+x^2");
+    check("CharacteristicPolynomial({{1, 1, 1}, {1, 1/2, 1/3}, {1, 2, 3}},x)", //
+        "-1/3-7/3*x+9/2*x^2-x^3");
+    check("CharacteristicPolynomial(N({{1, 1, 1}, {1, 1/2, 1/3}, {1, 2, 3}}),x)", //
+        "-0.333333-2.33333*x+4.5*x^2-x^3");
+    check("CharacteristicPolynomial({{1, 2*I}, {3 + 4*I, 5}}, z)", //
+        "13-I*6-6*z+z^2");
+  }
+
   @Test
   public void testCholeskyDecomposition() {
     check("matG=CholeskyDecomposition({{11.0,3.0},{3.0, 5.0}})", //

diff --git a/...library/matheclipse-core/src/test/java/org/matheclipse/core/system/LowercaseTestCase.java b/...library/matheclipse-core/src/test/java/org/matheclipse/core/system/LowercaseTestCase.java
@@ -2787,18 +2787,6 @@ public void testCharacters() {
         "{{\"t\",\"h\",\"i\"},{\"h\",\"i\",\"s\"},{\"i\",\"s\",\" \"},{\"s\",\" \",\"i\"},{\" \",\"i\",\"s\"},{\"i\",\"s\",\" \"},{\"s\",\" \",\"a\"},{\" \",\"a\",\" \"},{\"a\",\" \",\"s\"},{\" \",\"s\",\"t\"},{\"s\",\"t\",\"r\"},{\"t\",\"r\",\"i\"},{\"r\",\"i\",\"n\"},{\"i\",\"n\",\"g\"}}");
   }
 
-  @Test
-  public void testCharacteristicPolynomial() {
-    check("CharacteristicPolynomial({{a, b}, {c, d}}, x)", //
-        "-b*c+a*d-a*x-d*x+x^2");
-    check("CharacteristicPolynomial({{1, 1, 1}, {1, 1/2, 1/3}, {1, 2, 3}},x)", //
-        "-1/3-7/3*x+9/2*x^2-x^3");
-    check("CharacteristicPolynomial(N({{1, 1, 1}, {1, 1/2, 1/3}, {1, 2, 3}}),x)", //
-        "-0.333333-2.33333*x+4.5*x^2-x^3");
-    check("CharacteristicPolynomial({{1, 2*I}, {3 + 4*I, 5}}, z)", //
-        "13-I*6-6*z+z^2");
-  }
-
   @Test
   public void testCheck() {
     check("Check(0^(-42), failure)", //
@@ -26430,6 +26418,8 @@ public void testValueQ() {
 
   @Test
   public void testVariables() {
+    check("Variables(FactorInteger(1232))", //
+        "{}");
     check("Variables({x+y,x,z})", //
         "{x,y,z}");
     check("Variables(x + f(x)+Pi*E)", //