Looks like the criterion for figuring out when to stop iterating
depends on fpprec. Not surprisingly, if you load newton.mac
when a larger value of fpprec is in effect, it takes more iterations
or it fails to converge according to the criterion.
I think if you set newtonepsilon (? not sure about the name)
to a different value, it will change the behavior of newton.
best
Robert Dodier
On 11/2/10, Jaime Villate <villate at fe.up.pt> wrote:
> On Fri, 2010-10-22 at 17:29 -0700, James Redford wrote:
>> If maxima-init.mac has fpprec:32; or higher precision, then the below
>> happens:
>>
>> (%i1) load(mnewton);
>> (%o1) C:/program1/maxima/share/maxima/5.22.1/share/contrib/mnewton.mac
>> (%i2) mnewton(cos(x)=1/2,x,0.99);
>> mnewton: the process doesn't converge or it converges too slowly.
>> (%o2) []
>> (%i3)
>>
>>
>> If one then changes fpprec: in the interactive session, it has no effect:
>> mnewton still won't work with cos(x). Yet in the interactive session, if
>> maxima-init.mac has fpprec:31; or lower precision, one can set fpprec:
>> much higher and mnewton will work.
>>
>> This bug with mnewton does not occur with sin(x), tan(x) or atan(x), which
>> are some examples I tried.
>>
>> Below is the Maxima version I'm using:
>>
>> Maxima version: 5.22.1
>> Maxima build date: 11:48 8/13/2010
>> Host type: i686-pc-mingw32
>> Lisp implementation type: GNU Common Lisp (GCL)
>> Lisp implementation version: GCL 2.6.8
>>
>
> I observe the same bug with Maxima 5.22post/ SBCL 1.0.29.11
>
> Thank you very much for discovering and reporting that bug. We will
> investigate it and try to solve it.
>
> Regards,
> Jaime
>
>
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