introduce option "epsmin"

To define a minimum argument for some log() function invocations.
(most notably for the diode saturation current 'is')

src/frontend/com_option.c

@@ -48,6 +48,7 @@ com_option(wordlist *wl)
         printf("MaxOrder = %d\n", circuit->CKTmaxOrder);
         printf("xmu = %g\n", circuit->CKTxmu);
         printf("indverbosity = %d\n", circuit->CKTindverbosity);
+        printf("epsmin = %g\n", circuit->CKTepsmin);
 
         printf("\nTolerances (absolute):\n");
         printf("abstol      (current) = %g\n", circuit->CKTabstol);

src/frontend/spiceif.c

@@ -1411,6 +1411,7 @@ void com_snload(wordlist *wl)
     _t(CKTintegrateMethod);
     _t(CKTxmu);
     _t(CKTindverbosity);
+    _t(CKTepsmin);
 
     _t(CKTniState);
 

src/include/ngspice/cktdefs.h

@@ -293,6 +293,8 @@ struct CKTcircuit {
                            a safe operating area (SOA) check is executed */
     int CKTsoaMaxWarns; /* specifies the maximum number of SOA warnings */
 
+    double CKTepsmin; /* minimum argument value for some log functions, e.g. diode saturation current*/
+
     NGHASHPTR DEVnameHash;
     NGHASHPTR MODnameHash;
 

src/include/ngspice/optdefs.h

@@ -121,6 +121,7 @@ typedef struct {
 #define OPT_NOOPAC       68
 #define OPT_XMU          69
 #define OPT_INDVERBOSITY 70
+#define OPT_EPSMIN       71
 
 
 #ifdef XSPICE

src/include/ngspice/tskdefs.h

@@ -68,6 +68,7 @@ struct TSKtask {
     double TSKabsDv;                 /* abs limit for iter-iter voltage change */
     double TSKrelDv;                 /* rel limit for iter-iter voltage change */
     unsigned int TSKnoopac:1; /* flag for no OP calculation before AC */
+    double TSKepsmin;         /* minimum value for log */
 };
 
 #endif

src/spicelib/analysis/cktdojob.c

@@ -106,6 +106,7 @@ CKTdoJob(CKTcircuit *ckt, int reset, TSKtask *task)
     ckt->CKTtroubleNode  = 0;
     ckt->CKTtroubleElt  = NULL;
     ckt->CKTnoopac = task->TSKnoopac && ckt->CKTisLinear;
+    ckt->CKTepsmin = task->TSKepsmin;
 #ifdef NEWTRUNC
     ckt->CKTlteReltol = task->TSKlteReltol;
     ckt->CKTlteAbstol = task->TSKlteAbstol;

src/spicelib/analysis/cktntask.c

@@ -74,6 +74,7 @@ CKTnewTask(CKTcircuit *ckt, TSKtask **taskPtr, IFuid taskName, TSKtask **defPtr)
         tsk->TSKabsDv           = def->TSKabsDv;
         tsk->TSKrelDv           = def->TSKrelDv;
         tsk->TSKnoopac          = def->TSKnoopac;
+        tsk->TSKepsmin          = def->TSKepsmin;
 #ifdef NEWTRUNC
         tsk->TSKlteReltol       = def->TSKlteReltol;
         tsk->TSKlteAbstol       = def->TSKlteAbstol;
@@ -129,6 +130,7 @@ CKTnewTask(CKTcircuit *ckt, TSKtask **taskPtr, IFuid taskName, TSKtask **defPtr)
         tsk->TSKnodeDamping     = 0;
         tsk->TSKabsDv           = 0.5;
         tsk->TSKrelDv           = 2.0;
+        tsk->TSKepsmin          = 1e-28;
 
 #if (1) /*CDHW*/
     }

src/spicelib/analysis/cktsopt.c

@@ -169,6 +169,9 @@ CKTsetOpt(CKTcircuit *ckt, JOB *anal, int opt, IFvalue *val)
     case OPT_NOOPAC:
         task->TSKnoopac = (val->iValue != 0);
         break;
+    case OPT_EPSMIN:
+        task->TSKepsmin = val->rValue;
+        break;
 /* gtri - begin - wbk - add new options */
 #ifdef XSPICE
     case OPT_EVT_MAX_OP_ALTER:
@@ -323,7 +326,9 @@ static IFparm OPTtbl[] = {
  { "reldv", OPT_RELDV, IF_SET|IF_REAL,
         "Maximum relative iter-iter node voltage change" },
  { "noopac", OPT_NOOPAC, IF_SET|IF_FLAG,
-        "No op calculation in ac if circuit is linear" }
+        "No op calculation in ac if circuit is linear" },
+ { "epsmin", OPT_EPSMIN, IF_SET|IF_REAL,
+        "Minimum value for log" }
 };
 
 int OPTcount = NUMELEMS(OPTtbl);

src/spicelib/devices/cktinit.c

@@ -96,6 +96,7 @@ CKTinit(CKTcircuit **ckt)		/* new circuit to create */
     sckt->CKTvarHertz = 0;
     sckt->DEVnameHash = nghash_init_pointer(100);
     sckt->MODnameHash = nghash_init_pointer(100);
+    sckt->CKTepsmin = 1e-28;
 
 #ifdef XSPICE
 /* gtri - begin - wbk - allocate/initialize substructs */