From a89e5db571b9149eeef818705946b87596779f83 Mon Sep 17 00:00:00 2001
From: Holger Vogt <holger.vogt@uni-due.de>
Date: Thu, 21 Mar 2019 20:13:27 +0100
Subject: [PATCH] creating a linearized cutout of the original vector by
 defining the vectors lin-tstart, lin-tstop, and lin-tstep before issuing the
 'linearize' command

---
 examples/soi/ring51_40.sp |  8 +++++++-
 src/frontend/linear.c     | 23 +++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/examples/soi/ring51_40.sp b/examples/soi/ring51_40.sp
index b3ee80623..0c833466a 100644
--- a/examples/soi/ring51_40.sp
+++ b/examples/soi/ring51_40.sp
@@ -15,7 +15,7 @@ cout  buf ss 1pF
 * this is needed
 .option reltol=1e-4
 
-.tran 0.2n 10n
+.tran 0.2n 16n
 .print tran v(out25) v(out50)
 .include ./bsim4soi/nmos4p0.mod
 .include ./bsim4soi/pmos4p0.mod
@@ -46,8 +46,14 @@ xinv5 dd ss sub 4 out inv5
 if $?batchmode
 * do nothing
 else
+  save  out25 out50
   run
   plot out25 out50
+  let lin-tstart = 4n $ skip the start-up phase
+  let lin-tstop = 14n $ end earlier(just for demonstration)
+  let lin-tstep = 5p
+  linearize out25 out50
+  plot out25 out50
 endif
 .endc
 
diff --git a/src/frontend/linear.c b/src/frontend/linear.c
index 749481f47..63c622b41 100644
--- a/src/frontend/linear.c
+++ b/src/frontend/linear.c
@@ -17,6 +17,8 @@ Author: 1985 Wayne A. Christopher, U. C. Berkeley CAD Group
  * we determine by looking at the transient parameters in the CKT struct.
  * If no circuit is loaded, e.g. because the 'load' command has been used
  * to obtain data, try to get parameters from scale vector.
+ * Interpolation may be restricted to only a region of the input vector,
+ * thus creating a cutout of the original vector.
  */
 
 void
@@ -26,6 +28,7 @@ com_linearize(wordlist *wl)
     struct plot *new, *old;
     struct dvec *newtime, *v;
     struct dvec *oldtime;
+    struct dvec *lin;
     int len, i;
 
     if (!plot_cur || !plot_cur->pl_dvecs || !plot_cur->pl_scale) {
@@ -58,6 +61,26 @@ com_linearize(wordlist *wl)
         tstop = plot_cur->pl_scale->v_realdata[length - 1];
         tstep = (tstop - tstart) / (double)length;
     }
+
+    /* if this plot contains special vectors lin-tstart, lin-tstop or lin-tstep, use these instead */
+    lin = vec_fromplot("lin-tstart", plot_cur);
+    if (lin) {
+        fprintf(cp_out, "linearize tstart is set to: %8e\n", lin->v_realdata[0]);
+        tstart = lin->v_realdata[0];
+    }
+
+    lin = vec_fromplot("lin-tstop", plot_cur);
+    if (lin) {
+        fprintf(cp_out, "linearize tstop is set to: %8e\n", lin->v_realdata[0]);
+        tstop = lin->v_realdata[0];
+    }
+
+    lin = vec_fromplot("lin-tstep", plot_cur);
+    if (lin) {
+        fprintf(cp_out, "linearize tstep is set to: %8e\n", lin->v_realdata[0]);
+        tstep = lin->v_realdata[0];
+    }
+
     /* finally check if tstart, tstop and tstep are reasonable */
     if (((tstop - tstart) * tstep <= 0.0) || ((tstop - tstart) < tstep)) {
         fprintf(cp_err,