Fix bug in QP_solver and add respective test cases. The bug was that the artificial variable was not correctly expelled at the end of phase one in certain cases of redundant constraints.

(This is with permission of Laurent Rineau)

.gitattributes

@@ -3446,6 +3446,8 @@ QP_solver/test/QP_solver/test_default_bounds.cpp -text
 QP_solver/test/QP_solver/test_random_qp.cpp -text
 QP_solver/test/QP_solver/test_random_qp2.cpp -text
 QP_solver/test/QP_solver/test_solver.cout -text
+QP_solver/test/QP_solver/test_solver_data/cycle_cases/bug_stich.mps -text
+QP_solver/test/QP_solver/test_solver_data/cycle_cases/bug_taysom.mps -text
 QP_solver/test/QP_solver/test_solver_data/cycle_cases/helbling_001.mps -text
 QP_solver/test/QP_solver/test_solver_data/cycle_cases/helbling_248.mps -text
 QP_solver/test/QP_solver/test_solver_data/cycle_cases/helbling_39.mps -text

QP_solver/include/CGAL/QP_solver/QP_solver_impl.h

@@ -1255,12 +1255,7 @@ expel_artificial_variables_from_basis( )
     // explicitly are synchronized during transition from phaseI to phaseII 
     for (unsigned int i_ = static_cast<unsigned int>(qp_n + slack_A.size()); i_ < static_cast<unsigned int>(in_B.size()); ++i_) {
       if (is_basic(i_)) { 					// is basic
-        if (has_ineq) {
-	        row_ind = in_C[ art_A[i_ - qp_n - slack_A.size()].first];
-        } else {
-	        row_ind = art_A[i_ - qp_n].first;
-        }
-        
+        row_ind = in_B[i_];  
         
         //CGAL_qpe_assertion(row_ind >= 0);
         

QP_solver/test/QP_solver/test_solver_data/cycle_cases/bug_stich.mps

@@ -0,0 +1,105 @@
+* Description: Case that was sent in by Sebastian Stich. It used to exibit
+* a segfault in expel_artificial_variables (special artificial is linked to a
+* constraint that is not active).
+* Derivatives: none
+NAME MY_MPS
+ROWS
+  N obj
+  G c0
+  G c1
+  E c2
+  G c3
+  G c4
+  G c5
+  G c6
+  G c7
+  G c8
+  E c9
+  G c10
+  G c11
+  G c12
+  E c13
+  G c14
+  G c15
+  E c16
+  G c17
+  G c18
+  G c19
+  E c20
+COLUMNS
+  x0  c0  1
+  x0  c1  1
+  x0  c2  1
+  x0  c3  1
+  x0  c4  1
+  x1  c5  1
+  x1  c6  1
+  x1  c7  1
+  x1  c8  1
+  x1  c9  1
+  x1  c10  1
+  x1  c11  1
+  x2  c0  1
+  x2  c5  1
+  x2  c12  1
+  x2  c13  1
+  x3  c1  1
+  x3  c6  1
+  x3  c12  1
+  x3  c14  1
+  x3  c15  1
+  x3  c16  1
+  x4  c7  1
+  x4  c13  1
+  x4  c17  1
+  x4  c18  1
+  x4  c19  1
+  x5  c2  1
+  x6  c3  1
+  x6  c8  1
+  x6  c14  1
+  x6  c17  1
+  x6  c20  1
+  x7  c9  1
+  x8  c4  1
+  x8  c10  1
+  x8  c15  1
+  x8  c18  1
+  x8  c20  1
+  x9  c11  1
+  x9  c16  1
+  x9  c19  1
+RHS
+  rhs c0  1
+  rhs c1  1
+  rhs c2  1
+  rhs c3  1
+  rhs c4  1
+  rhs c5  1
+  rhs c6  1
+  rhs c7  1
+  rhs c8  1
+  rhs c9  1
+  rhs c10  1
+  rhs c11  1
+  rhs c12  1
+  rhs c13  1
+  rhs c14  1
+  rhs c15  1
+  rhs c16  1
+  rhs c17  1
+  rhs c18  1
+  rhs c19  1
+  rhs c20  1
+BOUNDS
+  UP  BND  x0  1
+  UP  BND  x1  1
+  UP  BND  x2  1
+  UP  BND  x3  1
+  UP  BND  x4  1
+  UP  BND  x5  1
+  UP  BND  x6  1
+  UP  BND  x7  1
+  UP  BND  x8  1
+  UP  BND  x9  1
+ENDATA

QP_solver/test/QP_solver/test_solver_data/cycle_cases/bug_taysom.mps

@@ -0,0 +1,30 @@
+* Description: Case that was sent in by William Taysom. It used to exibit
+* a segfault in expel_artificial_variables (special artificial is linked to a
+* constraint that is not active).
+NAME MY_MPS
+ROWS
+  N obj
+  E c0
+  G c1
+  G c2
+  G c3
+COLUMNS
+  x0  obj  1
+  x0  c0  1
+  x0  c1  1
+  x0  c2  1
+  x0  c3  1
+  x1  c0  1
+  x1  c1  1
+  x1  c3  1
+  x2  c0  1
+  x2  c1  1
+  x2  c2  1
+RHS
+  rhs c0  4
+  rhs c1  4
+  rhs c2  3
+  rhs c3  3
+BOUNDS
+  UP  BND  x0  2
+ENDATA