From e2cf397b6d28db7ce24e7bc3733976e48718d988 Mon Sep 17 00:00:00 2001
From: Holger Vogt <holger.vogt@uni-due.de>
Date: Fri, 9 Apr 2021 10:56:04 +0200
Subject: [PATCH] Restrict the limit for exp function (linear growth when
 exponent is larger than 14, commit [93a76d]) to the PSPICE compatibility
 mode.

---
 src/spicelib/parser/inpptree.c | 16 +++++++++++-----
 src/spicelib/parser/ptfuncs.c  |  5 +++--
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/src/spicelib/parser/inpptree.c b/src/spicelib/parser/inpptree.c
index 29c0f9240..3b4c7733c 100644
--- a/src/spicelib/parser/inpptree.c
+++ b/src/spicelib/parser/inpptree.c
@@ -5,6 +5,7 @@ Author: 1987 Wayne A. Christopher, U. C. Berkeley CAD Group
 //#define TRACE
 
 #include "ngspice/ngspice.h"
+#include "ngspice/compatmode.h"
 #include "ngspice/ifsim.h"
 #include "ngspice/iferrmsg.h"
 #include "ngspice/inpdefs.h"
@@ -448,11 +449,16 @@ static INPparseNode *PTdifferentiate(INPparseNode * p, int varnum)
             break;
 
         case PTF_EXP:                /* u > EXPARGMAX -> EXPMAX, that is exp(EXPARGMAX), else exp(u) */
-            arg1 = mkb(PT_TERN,
-                mkf(PTF_GT0, mkb(PT_MINUS, p->left, mkcon(EXPARGMAX))),
-                mkb(PT_COMMA,
-                    mkcon(EXPMAX),
-                    mkf(PTF_EXP, p->left)));
+            if (newcompat.ps) {
+                arg1 = mkb(PT_TERN,
+                    mkf(PTF_GT0, mkb(PT_MINUS, p->left, mkcon(EXPARGMAX))),
+                    mkb(PT_COMMA,
+                        mkcon(EXPMAX),
+                        mkf(PTF_EXP, p->left)));
+            }
+            else {                   /* exp(u) */
+                arg1 = mkf(PTF_EXP, p->left);
+            }
 
 #ifdef TRACE1
             printf("debug exp, %s, returns; ", __func__);
diff --git a/src/spicelib/parser/ptfuncs.c b/src/spicelib/parser/ptfuncs.c
index 4c376daa5..845f8b46a 100644
--- a/src/spicelib/parser/ptfuncs.c
+++ b/src/spicelib/parser/ptfuncs.c
@@ -215,11 +215,12 @@ PTcosh(double arg)
     return (cosh(arg));
 }
 
-/* Limit the exp: If arg > EXPARGMAX (arbitrarily selected to 14), continue with linear output */
+/* Limit the exp: If arg > EXPARGMAX (arbitrarily selected to 14), continue with linear output,
+   if compatmode PSPICE is selected*/
 double
 PTexp(double arg)
 {
-    if (arg > EXPARGMAX)
+    if (newcompat.ps && arg > EXPARGMAX)
         return EXPMAX * (arg - EXPARGMAX + 1.);
     else
         return (exp(arg));