hasse_deriv2.m

来自「在matlab中」· M 代码 · 共 28 行

function val = hasse_deriv2(Q,x,y,r,s,m)

% VALUE = hasse_deriv2(Q,x,y,r,s,q)
% 
% Takes the (r,s) Hasse mixed partial derivative of the polynomial
% Q(.,.) at the point (x,y).  The computation is done over the finite
% field GF(2^m).
%
% Q is a matrix of 
%
% If Q = sum_ij v_ij x^i y^j,
%
% then VALUE = sum_ij binom(i,r) binom(j,s) v_ij x^(i-a) y^(j-b) .

val = gf(0,m);

for ind1=(r+1):size(Q,1)
   for ind2=(s+1):size(Q,2)
      binomx = nchoosek(ind1-1,r);
      binomy = nchoosek(ind2-1,s);
      if ( (binomx/2 ~= floor(binomx/2)) && (binomy/2 ~= floor(binomy/2)) )
         val = val + Q(ind1,ind2) * x^(ind1-1 - r) * y^(ind2-1 -s);
      end
   end
end