Re: [ng-spice-devel] Pole-zero analysis issues.
On Sat, Jun 17, 2000 at 10:40:16AM +0200, Paolo Nenzi wrote:
> On Fri, 16 Jun 2000, Arno W. Peters wrote:
>
> > On Fri, Jun 16, 2000 at 06:30:44PM +0200, Paolo Nenzi wrote:
>
> > So far I haven't compiled any of the older versions to see what
> > version introduced the error. If somebody would step up to check
> > this?
>
> I have compiled the cktpx* code with PZDEBUG defined and run the
> simulation with the bridge filter:
>
> Circuit: * Bridge T Filter
>
> ngspice 1 -> run
> suggestion(0/0/4 | 0): init
> Guess
> * ( 1/ 1) 0 0 :: 0.524287999999998977074255890329 0 -19
> suggestion(1/0/4 | 0): init
> Guess
> * ( 2/ 2) 1 0 :: 0.525861388287999220736423922062 0 -19
> suggestion(1/0/4 | 0): init
> given 1 0 / 0 0 / 1 0
> suggestion(1/0/4 | 3): sym 1
> * ( 3/ 3) nan 0 :: nan nan -2147483648
> given 0 0 / 1 0 / nan 0
> suggestion(1/0/4 | 3): sym 1
> * ( 4/ 4) nan 0 :: nan nan -2147483648
> given 1 0 / nan 0 / nan 0
> suggestion(1/0/4 | 3): sym 1
> * ( 5/ 5) nan 0 :: nan nan -2147483648
> given nan 0 / nan 0 / nan 0
> suggestion(1/0/4 | 3): split right
> * ( 6/ 6) nan 0 :: nan nan -2147483648
> Aborted
I wouldn't know how to interpret the output. Perhaps prof. Newton can
tell us more about it.
> There are a lot of NANs, do not seems normal. The other circuit (the
> filt_rc.cir) ends in a segmentation violation (the output is attached
> below)
>
> [...]
> ALTER from: -99999999.9999999403953552246094 0
>
> internal error -- segmentation violation
The segment violation is due to the following line of code
(in cktpzstr.c, line 1120):
DEBUG(1) fprintf(stderr, "nt->next %g\n", nearto->prev->s.real);
Check it in the debugger, you'll find
nearto->prev == NULL
and thus nearto->prev->s.real naturally leads to a segmentation
fault.
I added some checks to circumvent this. They are checked into CVS.
Please try them out.
Regards,
--
Arno
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