Hi,
I use bfallroots function :
https://apps.sourceforge.net/mediawiki/maxima/index.php?title=Image:Centers_9_new.png
Can it be done for higher periods ? ( for me (GCL) it fails for period
10 and fpprec:150 or 256)
I have not found documentation of this function ( maybe I'm wrong).
If not maybe it will be good :
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bfallroots function is in cpoly package by Raymond Toy .
It finds roots of complex polynomials by Jenkins and Traub algorithm .
Source code with some comments is in file cpoly.lisp in src directory
( for example in Maxima-5.16.3\share\maxima\5.16.3\src )
How to use it :
load(cpoly); /* load package */
C:/PROGRA~1/MAXIMA~1.3/share/maxima/5.16.3/src/cpoly.lisp
g:c^15+8*c^14+28*c^13+60*c^12+94*c^11+116*c^10+114*c^9+94*c^8+69*c^7+44*c^6+26*c^5+14*c^4+5*c^3+2*c^2+c+1;
cc:bfallroots(expand(%i*g)=0);
[c=3.349323055974976b-1*%i+3.795135880159238b-1,c=5.627657614529819b-1*%i-5.04340175446244b-1,
c=3.795135880159238b-1-3.349323055974976b-1*%i,c=3.592592247580075b-1-6.425137371385424b-1*%i,
c=6.425137371385423b-1*%i+3.592592247580075b-1,c=-5.627657614529822b-1*%i-5.043401754462439b-1,
c=-9.865809762809012b-1*%i-4.421235770407143b-2,c=9.865809762808959b-1*%i-4.421235770406282b-2,
c=1.100269537292701b0*%i-1.980420993642625b-1,c=-1.100269537292691b0*%i-1.980420993642588b-1,
c=-3.803209634726519b-1*%i-1.256367930068198b0,c=3.803209634727577b-1*%i-1.256367930068256b0,
c=-2.946422217180025b-13*%i-1.625413725122748b0,c=3.216381042965481b-13*%i-1.860782522205917b0,
c=-1.369842898493791b-13*%i-1.9854242530536b0]
cc:map(rhs,cc);/* remove string "c=" */
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HTH
Adam