Problem to specify log sweep

[dwarning]

Made yesterday a compile from current branch with mingw-ucrt64 and have now problem to specify a log parameter sweep. The widget did not calculate the number of total points anymore. Simulation fails.

[ra3xdh]

According the chapter 11.3.2 of the Ngspice manual the log sweep typ is not supported for DC simulation. The DC+ParSweep is converted to SPICE DC sweep. You cannot define log sweep for it.

[ra3xdh]

This simulation type will work only for Qucsator. Something is wrong with points calculation. When I input 10 point per decade the total points gives 1. This may appear after #1054 @iwbnwif , Please have a look.

[dwarning]

No, with your provided executable 24.4.1 it works very well, as all the time:

[ra3xdh]

To be honestly I cannot remember when I used the LOG Parameter Sweep the last time and if it was operational before.

[ra3xdh]

No, with your provided executable 24.4.1 it works very well, as all the time:

It works, but the result is totally wrong. The step is linear. The DC simulation type supports only linear step. It generates the following netlist line (for another schematic):

dc i1 1e-09 0.1 0.000833333

But the point number calculation is correct. I suspect it was broken after #1054

[dwarning]

OK, now I see. My thought was initial that qucs-s transfer this to a pointwise simulation.
Correct would be that log disappears if I specify DC1 simulation type.
How the step 0.000833333 is calculated?

[ra3xdh]

How the step 0.000833333 is calculated?

step=(stop-start)/number

For my example (100m-1n)/121. This is not possible to fix, because DC doesn't support LOG sweep like AC.

[dwarning]

I tried List with the provided binary.

This goes total wrong:

dc i1 0 2.63144e-312 1.17439e-311

In the end only lin sweep should be allowed and enumerated for ngspice active.

[ra3xdh]

I have identified the root of the wrong calculation. The error is gone after the following patch:

diff --git a/qucs/components/componentdialog.cpp b/qucs/components/componentdialog.cpp
index 4f94f71e..92397082 100644
--- a/qucs/components/componentdialog.cpp
+++ b/qucs/components/componentdialog.cpp
@@ -597,13 +597,13 @@ void ComponentDialog::updateSweepProperty(const QString& property)
       if (property == "Start" || property == "Stop" || property == "Points" || property == "All")
       {
         double points = str2num(pointsEdit->value());
-        double step = (points - 1.0) / log10(fabs((stop < 1.0 ? 1.0 : stop) / (start < 1.0 ? 1.0 : start)));
+        double step = (points - 1.0) / log10(fabs((stop) / (start)));
         sweepParamWidget["Step"]->setValue(misc::num2str(step));
       }
       else if (property == "Step")
       {
         double step = str2num(sweepParamWidget["Step"]->value());
-        double points = log10(fabs((stop < 1.0 ? 1.0 : stop) / (start < 1.0 ? 1.0 : start))) * step + 1.0;
+        double points = log10(fabs((stop) / (start))) * step + 1.0;
         pointsEdit->setValue(QString::number(round(points), 'g', 16));
       }     
     }

@iwbnwif What was the purpose of stop < 1.0 ? 1.0 : stop in the equation? The start and stop value may be less than one. The value greater than zero must be allowed.

[ra3xdh]

Log limits calculation is fixed by #1198. The disable of log+DC sweep will be implemented as part of #974, because it depends on simulator.