Fixed a bug in SMPpreOrder and let KLU digest an empty matrix

src/include/ngspice/klu.h

@@ -130,6 +130,7 @@ typedef struct          /* 64-bit version (otherwise same as above) */
 /* Common->status values */
 #define KLU_OK 0
 #define KLU_SINGULAR (1)            /* status > 0 is a warning, not an error */
+#define KLU_EMPTY_MATRIX (2)        /* Modified by Francesco Lannutti - Case when the matrix is empty */
 #define KLU_OUT_OF_MEMORY (-2)
 #define KLU_INVALID (-3)
 #define KLU_TOO_LARGE (-4)          /* integer overflow has occured */

src/maths/KLU/klu_analyze_given.c

@@ -41,6 +41,12 @@ KLU_symbolic *KLU_alloc_symbolic
 
     if (n <= 0 || Ap == NULL || Ai == NULL)
     {
+        if (n == 0)
+        {
+            Common->status = KLU_EMPTY_MATRIX ;
+            return (NULL) ;
+        }
+
         /* Ap and Ai must be present, and n must be > 0 */
         Common->status = KLU_INVALID ;
         return (NULL) ;

src/maths/KLU/klu_factor.c

@@ -402,6 +402,10 @@ KLU_numeric *KLU_factor         /* returns NULL if error, or a valid
     {
         return (NULL) ;
     }
+    if (Common->status == KLU_EMPTY_MATRIX)
+    {
+        return (NULL) ;
+    }
     Common->status = KLU_OK ;
     Common->numerical_rank = EMPTY ;
     Common->singular_col = EMPTY ;

src/maths/KLU/klu_refactor.c

@@ -46,6 +46,10 @@ Int KLU_refactor        /* returns TRUE if successful, FALSE otherwise */
     {
         return (FALSE) ;
     }
+    if (Common->status == KLU_EMPTY_MATRIX)
+    {
+        return (FALSE) ;
+    }
     Common->status = KLU_OK ;
 
     if (Numeric == NULL)

src/maths/KLU/klu_solve.c

@@ -41,6 +41,10 @@ Int KLU_solve
     {
         return (FALSE) ;
     }
+    if (Common->status == KLU_EMPTY_MATRIX)
+    {
+        return (FALSE) ;
+    }
     if (Numeric == NULL || Symbolic == NULL || d < Symbolic->n || nrhs < 0 ||
         B == NULL)
     {

src/maths/KLU/klu_tsolve.c

@@ -46,6 +46,10 @@ Int KLU_tsolve
     {
         return (FALSE) ;
     }
+    if (Common->status == KLU_EMPTY_MATRIX)
+    {
+        return (FALSE) ;
+    }
     if (Numeric == NULL || Symbolic == NULL || d < Symbolic->n || nrhs < 0 ||
         B == NULL)
     {

src/maths/KLU/klusmp.c

@@ -207,6 +207,11 @@ SMPcLUfac (SMPmatrix *Matrix, double PivTol)
         spSetComplex (Matrix->SPmatrix) ;
         ret = klu_z_refactor (Matrix->CKTkluAp, Matrix->CKTkluAi, Matrix->CKTkluAx_Complex,
                               Matrix->CKTkluSymbolic, Matrix->CKTkluNumeric, Matrix->CKTkluCommon) ;
+
+        if (Matrix->CKTkluCommon->status == KLU_EMPTY_MATRIX)
+        {
+            return 0 ;
+        }
         return (!ret) ;
     } else {
         spSetComplex (Matrix->SPmatrix) ;
@@ -232,6 +237,11 @@ SMPluFac (SMPmatrix *Matrix, double PivTol, double Gmin)
         LoadGmin_CSC (Matrix->CKTdiag_CSC, Matrix->CKTkluN, Gmin) ;
         ret = klu_refactor (Matrix->CKTkluAp, Matrix->CKTkluAi, Matrix->CKTkluAx,
                             Matrix->CKTkluSymbolic, Matrix->CKTkluNumeric, Matrix->CKTkluCommon) ;
+
+        if (Matrix->CKTkluCommon->status == KLU_EMPTY_MATRIX)
+        {
+            return 0 ;
+        }
         return (!ret) ;
 
 //        if (ret == 1)
@@ -269,7 +279,13 @@ SMPcReorder (SMPmatrix *Matrix, double PivTol, double PivRel, int *NumSwaps)
             Matrix->CKTkluNumeric = klu_z_factor (Matrix->CKTkluAp, Matrix->CKTkluAi, Matrix->CKTkluAx_Complex, Matrix->CKTkluSymbolic, Matrix->CKTkluCommon) ;
 
         if (Matrix->CKTkluNumeric == NULL)
+        {
+            if (Matrix->CKTkluCommon->status == KLU_EMPTY_MATRIX)
+            {
+                return 0 ;
+            }
             return 1 ;
+        }
         else
             return 0 ;
     } else {
@@ -299,7 +315,13 @@ SMPreorder (SMPmatrix *Matrix, double PivTol, double PivRel, double Gmin)
             Matrix->CKTkluNumeric = klu_factor (Matrix->CKTkluAp, Matrix->CKTkluAi, Matrix->CKTkluAx, Matrix->CKTkluSymbolic, Matrix->CKTkluCommon) ;
 
         if (Matrix->CKTkluNumeric == NULL)
+        {
+            if (Matrix->CKTkluCommon->status == KLU_EMPTY_MATRIX)
+            {
+                return 0 ;
+            }
             return 1 ;
+        }
         else
             return 0 ;
     } else {
@@ -459,7 +481,16 @@ SMPpreOrder (SMPmatrix *Matrix)
     {
         Matrix->CKTkluSymbolic = klu_analyze (Matrix->CKTkluN, Matrix->CKTkluAp, Matrix->CKTkluAi, Matrix->CKTkluCommon) ;
 
-        return 0 ;
+        if (Matrix->CKTkluSymbolic == NULL)
+        {
+            if (Matrix->CKTkluCommon->status == KLU_EMPTY_MATRIX)
+            {
+                return 0 ;
+            }
+            return 1 ;
+        } else {
+            return 0 ;
+        }
     } else {
         spMNA_Preorder (Matrix->SPmatrix) ;
         return spError (Matrix->SPmatrix) ;