fromcrtpoly.m

来自「压缩文件中是Error Correction Coding - Mathemat」· M 代码 · 共 39 行

function [f,gamma] = fromcrtpoly(y,m,gammain)
% function [f,gamma] = fromcrtpoly(y,m,gammain)
% function [f] = fromcrtpoly(y,m)
% function [f,gamma] = fromcrtpoly(y,m)
% function [f] = fromcrtpoly(y,mp,gammain)
%
% Compute the representation of the polynomial f using the Chinese Remainder
% Theorem (CRT) using the moduli m = [m1,m2,...,mr].  It is assumed 
% (without checking) that the moduli are relatively prime.  
% Optionally, the gammas may be passed in (speeding computation), and
% are returned as optional return values.

% Copyright 2004 by Todd K. Moon
% Permission is granted to use this program/data
% for educational/research only

r = length(y);
mp = 1;
for i=1:r
  mp = polymult(mp,m{i});
end

if(nargin==2)
  f = 0;
  for i=1:r
    [q,rm] = polydiv(mp,m{i});
    [g,b,y1] = gcdpoly(q,m{i});
    gamma{i} = polymult(q,b);
    f = polyadd(f,polymult(gamma{i},y{i}));
  end
else            % use the passed-in gammas
  f = 0;
  for i=1:r
    f = polyadd(f,polymult(gammain{i},y{i}));
  end
  gamma = gammain;
end
% Take the result modulo m
[q,f] = polydiv(f,mp);