From bc12b325420a8b0f1d8c7f863a15e1f17c30cf87 Mon Sep 17 00:00:00 2001
From: rlar <rlar>
Date: Fri, 30 Mar 2018 21:35:56 +0200
Subject: [PATCH] spicelib/devices/{sw,csw}, fix CKTtime += CKTdelmin issue

don't CKTtrunc when we approach the projected switch point by more
than  100 * DBL_EPSILON * CKTtime

to make sure VSRC / ISRC has still room to produce values.

FIXME,
  dctran.c might suffer from a similiar, non sw/csw related issue.
  it might be necessairy to generally replace CKTdelmin by
    MAX(CKTdelmin, HEADROOM * DBL_EPSILON * CKTtime)
---
 src/spicelib/devices/csw/cswtrunc.c | 5 +++++
 src/spicelib/devices/sw/swtrunc.c   | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/src/spicelib/devices/csw/cswtrunc.c b/src/spicelib/devices/csw/cswtrunc.c
index 7662b12a3..66bd7e02f 100644
--- a/src/spicelib/devices/csw/cswtrunc.c
+++ b/src/spicelib/devices/csw/cswtrunc.c
@@ -17,6 +17,7 @@ CSWtrunc(GENmodel *inModel, CKTcircuit *ckt, double *timeStep)
     CSWmodel *model = (CSWmodel *) inModel;
     CSWinstance *here;
     double   lastChange, maxChange, maxStep, ref;
+    const double reltime = 100 * DBL_EPSILON;
 
     for (; model; model = CSWnextModel(model))
         for (here = CSWinstances(model); here; here = CSWnextInstance(here)) {
@@ -29,6 +30,8 @@ CSWtrunc(GENmodel *inModel, CKTcircuit *ckt, double *timeStep)
                     maxChange =
                         (ref - ckt->CKTstate0[here->CSWctrlvalue]) * 0.75;
                     maxStep = maxChange / lastChange * ckt->CKTdeltaOld[0];
+                    if (maxStep < ckt->CKTtime * reltime)
+                        maxStep = ckt->CKTtime * reltime;
                     if (maxStep < ckt->CKTdelmin)
                         maxStep = ckt->CKTdelmin;
                     if (*timeStep > maxStep)
@@ -40,6 +43,8 @@ CSWtrunc(GENmodel *inModel, CKTcircuit *ckt, double *timeStep)
                     maxChange =
                         (ref - ckt->CKTstate0[here->CSWctrlvalue]) * 0.75;
                     maxStep = maxChange / lastChange * ckt->CKTdeltaOld[0];
+                    if (maxStep < ckt->CKTtime * reltime)
+                        maxStep = ckt->CKTtime * reltime;
                     if (maxStep < ckt->CKTdelmin)
                         maxStep = ckt->CKTdelmin;
                     if (*timeStep > maxStep)
diff --git a/src/spicelib/devices/sw/swtrunc.c b/src/spicelib/devices/sw/swtrunc.c
index ef3165322..f29199067 100644
--- a/src/spicelib/devices/sw/swtrunc.c
+++ b/src/spicelib/devices/sw/swtrunc.c
@@ -17,6 +17,7 @@ SWtrunc(GENmodel *inModel, CKTcircuit *ckt, double *timeStep)
     SWmodel *model = (SWmodel *) inModel;
     SWinstance *here;
     double   lastChange, maxChange, maxStep, ref;
+    const double reltime = 100 * DBL_EPSILON;
 
     for (; model; model = SWnextModel(model))
         for (here = SWinstances(model); here; here = SWnextInstance(here)) {
@@ -29,6 +30,8 @@ SWtrunc(GENmodel *inModel, CKTcircuit *ckt, double *timeStep)
                     maxChange =
                         (ref - ckt->CKTstate0[here->SWctrlvalue]) * 0.75;
                     maxStep = maxChange / lastChange * ckt->CKTdeltaOld[0];
+                    if (maxStep < ckt->CKTtime * reltime)
+                        maxStep = ckt->CKTtime * reltime;
                     if (maxStep < ckt->CKTdelmin)
                         maxStep = ckt->CKTdelmin;
                     if (*timeStep > maxStep)
@@ -40,6 +43,8 @@ SWtrunc(GENmodel *inModel, CKTcircuit *ckt, double *timeStep)
                     maxChange =
                         (ref - ckt->CKTstate0[here->SWctrlvalue]) * 0.75;
                     maxStep = maxChange / lastChange * ckt->CKTdeltaOld[0];
+                    if (maxStep < ckt->CKTtime * reltime)
+                        maxStep = ckt->CKTtime * reltime;
                     if (maxStep < ckt->CKTdelmin)
                         maxStep = ckt->CKTdelmin;
                     if (*timeStep > maxStep)