On 2015-09-01 07:25 AM (-4), Norbert Kern wrote:
> #declare IterFn =
> function (N, Re, Im, Zr, Zi) {
>          select (
>                  N > 300 | Zr*Zr+Zi*Zi > 4,
>                  0,
>                  IterFn (N+1, Re, Im, Zr*Zr-Zi*Zi+Re, 2*abs (Zr*Zi)+Im),
>                  N/300
>          )
> }

Reducing the recursion level does not prevent the crash.  I tried all 
the way down to 1.

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Cousin Ricky <ric### [at] yahoocom> wrote:
> On 2015-09-01 07:25 AM (-4), Norbert Kern wrote:
> > #declare IterFn =
> > function (N, Re, Im, Zr, Zi) {
> >          select (
> >                  N > 300 | Zr*Zr+Zi*Zi > 4,
> >                  0,
> >                  IterFn (N+1, Re, Im, Zr*Zr-Zi*Zi+Re, 2*abs (Zr*Zi)+Im),
> >                  N/300
> >          )
> > }
>
> Reducing the recursion level does not prevent the crash.  I tried all
> the way down to 1.

The reason for this, I believe, is that pic doesn't support recursive functions.
You can get away with exactly one, if -and only if- it is defined before
anything else in the file.

Regards,
A.D.B.

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"Anthony D. Baye" <Sha### [at] spamnomorehotmailcom> wrote:
> Cousin Ricky <ric### [at] yahoocom> wrote:
> > On 2015-09-01 07:25 AM (-4), Norbert Kern wrote:
> > > #declare IterFn =
> > > function (N, Re, Im, Zr, Zi) {
> > >          select (
> > >                  N > 300 | Zr*Zr+Zi*Zi > 4,
> > >                  0,
> > >                  IterFn (N+1, Re, Im, Zr*Zr-Zi*Zi+Re, 2*abs (Zr*Zi)+Im),
> > >                  N/300
> > >          )
> > > }
> >
> > Reducing the recursion level does not prevent the crash.  I tried all
> > the way down to 1.
>
> The reason for this, I believe, is that pic

pov* -- stupid ipod.

anyway... it causes your system to crash, or just causes povray to crash?

Regards,
A.D.B.

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"Anthony D. Baye" <Sha### [at] spamnomorehotmailcom> wrote:

> anyway... it causes your system to crash, or just causes povray to crash?
>
> Regards,
> A.D.B.

Hi Anthony,
only povray. I condensed the problem in perhaps 100 steps by deleting nearly
everything including tests with 3.6 and on a second pc.
There were similar problems with other (typically recursive) functions in the
past, but here I was getting angry, because I like this special fractal very
much.

Norbert

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>> declaring *any* function before your IterFn causes the crash.
>

>
> Thanks very much

You can get around the problem by unrolling the iteration into 300 
different functions in an array:


#declare MAX_ITERATIONS = 300;

#declare Fns = array[MAX_ITERATIONS];
#declare Fns[MAX_ITERATIONS-1] = function (N, Re, Im, Zr, Zi) { 0 }
#local ITERATION = MAX_ITERATIONS-2;
#while(ITERATION>=0)

#declare Fns[ITERATION] =
function (N, Re, Im, Zr, Zi) {
         select (
                 Zr*Zr+Zi*Zi > 4,
                 0,
                 Fns[ITERATION+1] (N+1, Re, Im, Zr*Zr-Zi*Zi+Re, 2*abs 
(Zr*Zi)+Im),
                 ITERATION/300
         )
}

#local ITERATION=ITERATION-1;
#end

#declare BurningShip = function (Re, Im) {Fns[0] (0, Re, Im, Re, Im)}

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scott <sco### [at] scottcom> wrote:

> You can get around the problem by unrolling the iteration into 300
> different functions in an array:
>
>
> #declare MAX_ITERATIONS = 300;
>
> #declare Fns = array[MAX_ITERATIONS];
> #declare Fns[MAX_ITERATIONS-1] = function (N, Re, Im, Zr, Zi) { 0 }
> #local ITERATION = MAX_ITERATIONS-2;
> #while(ITERATION>=0)
>
> #declare Fns[ITERATION] =
> function (N, Re, Im, Zr, Zi) {
>          select (
>                  Zr*Zr+Zi*Zi > 4,
>                  0,
>                  Fns[ITERATION+1] (N+1, Re, Im, Zr*Zr-Zi*Zi+Re, 2*abs
> (Zr*Zi)+Im),
>                  ITERATION/300
>          )
> }
>
> #local ITERATION=ITERATION-1;
> #end
>
> #declare BurningShip = function (Re, Im) {Fns[0] (0, Re, Im, Re, Im)}

wow, it works!
Thank you very much.

Norbert

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Am 01.09.2015 um 13:25 schrieb Norbert Kern:
> Hi,
> here is minimal code for the famous burning ship fractal.
> It renders fine as long as I don't include functions.inc (in another context I
> need functions.inc).
> Does anybody know the reason?

Yes: POV-Ray doesn't officially support recursive functions.

It works in /some/ cases, but has some quite severe limitations; my
personal recommendation would be to create one function for each level
of recursion; that shouldn't be too difficult using a #for loop and the
Parse_String() macro from strings.inc.

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scott <sco### [at] scottcom> wrote:
> >> declaring *any* function before your IterFn causes the crash.
> >

> >
> > Thanks very much
>
> You can get around the problem by unrolling the iteration into 300
> different functions in an array:

Wouldn't it use less memory to have only two functions that you #declare and
#undef within the loop?
http://news.povray.org/povray.binaries.scene-files/thread/%3C4ddda4d9%40news.povray.org%3E/

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"Samuel Benge" <stb### [at] hotmailcom> wrote:
> scott <sco### [at] scottcom> wrote:
> > You can get around the problem by unrolling the iteration into 300
> > different functions in an array:
>
> Wouldn't it use less memory to have only two functions that you #declare and
> #undef within the loop?

Nevermind, I'm pretty sure using only two doesn't save memory :/

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Am 02.09.2015 um 18:06 schrieb Samuel Benge:
> "Samuel Benge" <stb### [at] hotmailcom> wrote:
>> scott <sco### [at] scottcom> wrote:
>>> You can get around the problem by unrolling the iteration into 300
>>> different functions in an array:
>>
>> Wouldn't it use less memory to have only two functions that you #declare and
>> #undef within the loop?
> 
> Nevermind, I'm pretty sure using only two doesn't save memory :/

... and you're pretty right ;)

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