Changeset 9291f85

Timestamp:

Jan 10, 2010, 7:25:50 PM (16 years ago)

Author:

Frederik Heber <heber@…>

Children:

9cdbee

Parents:

7b991d

Message:

Added Determinant() function to class GSLMatrix.

• new function GSLMatrix::Determinant() which calculates the determinant for square matrices by LU decomposition.

Signed-off-by: Frederik Heber <heber@tabletINS.(none)>

Location:

molecuilder/src

Files:

• gslmatrix.cpp (modified) (1 diff)
• unittests/gslmatrixsymmetricunittest.cpp (modified) (1 diff)

molecuilder/src/gslmatrix.cpp

@@ -229 +229 @@
     return (gsl_linalg_cholesky_decomp (matrix) != GSL_EDOM);
 };
+
+
+/** Calculates the determinant of the matrix.
+ * if matrix is square, uses LU decomposition.
+ */
+double GSLMatrix::Determinant()
+{
+  int signum = 0;
+  assert (rows == columns && "Determinant can only be calculated for square matrices.");
+  gsl_permutation *p = gsl_permutation_alloc(rows);
+  gsl_linalg_LU_decomp(matrix, p, &signum);
+  gsl_permutation_free(p);
+  return gsl_linalg_LU_det(matrix, signum); 
+};
+

molecuilder/src/unittests/gslmatrixsymmetricunittest.cpp

@@ -247 +247 @@
   m->SetFromDoubleArray(array);
   CPPUNIT_ASSERT_EQUAL( true, m->IsPositiveDefinite() );
+
+  //determinant
+  m->SetIdentity();
+  CPPUNIT_ASSERT_EQUAL( 1., m->Determinant() );
+
+  m->SetZero();
+  CPPUNIT_ASSERT_EQUAL( 0., m->Determinant() );
+
+  m->Set( 0, 0, 1.);
+  m->Set( 1, 1, 1.);
+  m->Set( 2, 1, 1.);
+  CPPUNIT_ASSERT_EQUAL( 0., m->Determinant() );
+  
+  double array2[] = { 2., 0., 1.,
+                     -3., 1., 1.,
+                     1., 5.5, 1. };
+  m->SetFromDoubleArray(array2);
+  CPPUNIT_ASSERT_EQUAL( -26.5, m->Determinant() );
 };