Re and more

Hi !

First of all Thanks for your previous answers, i will test it as soon 
as possible.

Some advised me to let gnucap choose its step size but I would like to 
know how to let it do so because when I don't set the stepsize the first 
time I use the command "tran" it doesn't work saying it misses the 
stepsize.

Thanks again.


Le 2013-01-04 18:00, [email protected] a écrit :
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>    1. Re: computing time (al davis)
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 3 Jan 2013 22:39:38 -0500
> From: al davis <[email protected]>
> To: [email protected]
> Subject: Re: [Help-gnucap] computing time
> Message-ID: <[email protected]>
> Content-Type: Text/Plain;  charset="utf-8"
>
> On Wednesday 02 January 2013, Romain GAILLETON wrote:
>> Before consider the following questions, you have to know
>> that we don?t  care of the accuracy of the voltage
>> calculated. We are working on a 110V scheme and we just want
>> to know if the wire are undervoltage or not (the voltage are
>> binarize by another application).
>> I would like to ask the several questions:
>
>> 1.      Which parameters can we use for reduce this computing
>> time?
>
> The defaults are intended for the usual IC-analog circuits.  If
> you are doing something different, you may want to change them.
>
> Reltol is relative, so probably ok as is.
>
> abstol, vntol are absolute.  You might want tolerances that
> might seem big to otherwise ...  how about vntol=1 volt?  or
> more?
>
> Is there feedback in your circuit?
>
> Is it linear except for the switches?
>
> Really a POWER circuit ..
>
> vfloor= 1.f
> voltage floor .. try 1 volt?
>
> roundofftol= 100.f
> 100 femptamps???  try .001 (1 milliamp)
>
> gmin= 1.p
> 1 picomho,  10^12 ohms.
> I get the feeling 100k is big for you .
> try gmin=1e-6
>
>
> short= 10.u  reltol= 0.001
>
> abstol= 1.p
> controls currents to 1 picoamp ..  .001 amps good enough??
>
> vntol= 1.u
> controls voltage to 1 microvolt   ..  1 volt good enough???
>
> chgtol= 10.f
> controls charge to 10 femtocoulombs ..
> ignored if you are using Euler.
>
> bypasstol= 0.1  loadtol= 0.1
> How aggressive to bypass.
> It probably doesn't matter with no semiconductors.
> 0.1 means 10x tighter than final tolerance.
>
> * iteration limiting and heuristics
> .options  itl1=100  itl2=50  itl3=6  itl4=20  itl5=0  itl6=5000
> itl7=1  itl8=99
> These are limits, when to give up.  You shouldn't be getting
> convergence failures with this circuit.  Probably no more than 3
> iterations on each step anyway.
>
> itermin=1
> Number of extra check iterations to do to insure accuracy, to
> protect against false convergence.  try itermin=0.
>
> vmax= 5.  vmin=-5.
> Convergence heuristics .. probably doesn't matter here, but it
> is best to make these numbers a little bigger than anything you
> expect to see.  vmax=150 vmin=-150 ????
>
> dampmax= 1.  dampmin= 0.5  dampstrategy=0
> These only come in when having trouble converging.  Mostly it is
> a way of upsetting Newton loops to get out of limit cycles.
>
> dtmin= 1.p
> The minimum time step is 1 picosecond.
> .001 seconds good enough for you??
>
>
> dtratio= 1.G  trstepgrow= 1.E+99  trstephold= 1.E+99
> trstepshrink= 2.  trreject= 0.5
>
> trsteporder=3
> Adjust stepping based on cubic splines.
> probably best left alone.
>
> trstepcoef1= 0.25  trstepcoef2= 0.04166667  trstepcoef3=
> 0.005208333
> these best left alone.
>
>> 2.      Is there an option which would allow Gnucap to
>> recalculate only the nodes where the voltage have changed?
>
> It sort of does now.
>
>
>
>> 3.      Is there an option which could allow us to send to
>> the output only  the nodes which are in a range?
>> Example: ?print tran v(nodes) ?  Which nodes are between 0 to
>> 4000
>
> Node names are strings.   Wildcards * and ? are supported.  With
> clever naming, selection can be very simple.
>
>> 4.      Is the time given by acct the real computing time?
> (or the status command)
>
> Yes.
>
>> 5.      Could it be possible to reduce the computing time
>> under 500ms in  your opinion?
>
> don't know ..
>
> but look at what stat tells you ... where is it spending the
> time?
>
> add "trace all" to the tran command to see all steps.
>
> add a probe "iter(0)" to show how many iterations on a step.
>
> There is a problem with read-in time in the snapshot.  Adding a
> feature (in the function "find_looking_out") made it slow.  Need
> to change the search method.  If readin dominates, try an older
> version, or comment out the call to find_looking_out, if you
> don't need it.
>
>
>
>
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