Reverse stepsize and finaltime in optran command,

stepsize first as in tran command.

README.optran

@@ -43,4 +43,9 @@ simulation when all nodes have become stable, might be desirable,
 but has not yet been implemented.
 One also may use the optran for a first transient simulation, maybe
 with different step sizes, before the next (tran, ac, pz, noise)
-simulation is commencing.
+simulation is commencing. So you may reach a certain bias point
+quickly and with coarse time steps, and then continue with fine
+steps to see details. For example a power amp in electro-thermal
+simulation may run for some seconds (minutes?) until the final
+temperature is reached, and then the detailed transient or
+an ac simulation starts.

examples/optran/script-optran.txt

@@ -11,8 +11,8 @@ else
 *** script for standard ngspice
 * Start optran without first iteration,
 * without gmin stepping and without src stepping
-* optran duration 4s, step size 10 ms
-optran 1 0 0 4 1e-2 0
+* optran step size 10 ms, duration 40s,
+optran 1 0 0 1e-2 4 0
 tran 1u 10m
 echo
 * output power
@@ -47,7 +47,8 @@ tran 1u 100m
 fft out
 set xbrushwidth=4
 set color0=white
+plot mag(out) xlimit 0 10k
+* to see the harmonics
 plot mag(out) xlimit 0 10k ylimit 0 30m
-
 end
 .endc

src/spicelib/analysis/optran.c

@@ -50,11 +50,15 @@ static double opramptime = 0.;
     CKTnoOpIter (default 0, set by 'option noopiter')
     CKTnumGminSteps
     CKTnumSrcSteps
-    opfinaltime
     opstepsize
+    opfinaltime
     opramptime
-*/
 
+    A typical command may be
+    optran 1 0 0 50u 10m 0
+    (no initial iteration, no gmin stepping, no source stepping,
+    stepsize for optran 50 us, optran run until 10 ms, no supply ramping
+    */
 void com_optran(wordlist* wl) {
     wordlist* wltmp = wl;
     char* stpstr;
@@ -76,11 +80,11 @@ void com_optran(wordlist* wl) {
     if ((errno == ERANGE) || (*stpstr != '\0'))
         goto bugquit;
     wltmp = wltmp->wl_next;
-    opfinaltime = strtod(wltmp->wl_word, &stpstr);
+    opstepsize = strtod(wltmp->wl_word, &stpstr);
     if ((errno == ERANGE) || (*stpstr != '\0'))
         goto bugquit;
     wltmp = wltmp->wl_next;
-    opstepsize = strtod(wltmp->wl_word, &stpstr);
+    opfinaltime = strtod(wltmp->wl_word, &stpstr);
     if ((errno == ERANGE) || (*stpstr != '\0'))
         goto bugquit;
     wltmp = wltmp->wl_next;