function [x,N]= BJ(A,b,x0,d,eps,M)
if nargin==4
eps= 1.0e-6;
M = 10000;
elseif nargin<4
error
return
elseif nargin ==5
M = 10000; %参数的默认值
end
NS = size(A);
n = NS(1,1);
if(sum(d) ~= n)
disp('分块错误!');
return;
end
bnum = length(d);
bs = ones(bnum,1);
for i=1:(bnum-1)
bs(i+1,1)=sum(d(1:i))+1;
%获得对角线上每个分块矩阵元素索引的起始值
end
DB = zeros(n,n);
for i=1:bnum
endb = bs(i,1)+d(i,1)-1;
DB(bs(i,1):endb,bs(i,1):endb)=A(bs(i,1):endb,bs(i,1):endb);
%求A的对角分块矩阵
end
for i=1:bnum
endb = bs(i,1)+d(i,1)-1;
invDB(bs(i,1):endb,bs(i,1):endb)=inv(DB(bs(i,1):endb,bs(i,1):endb));
%求A的对角分块矩阵的逆矩阵
end
N = 0;
tol = 1;
while tol>=eps
x = invDB*(DB-A)*x0+invDB*b; %由于LB+DB=DB-A
N = N+1; %迭代步数
tol = norm(x-x0); %前后两步迭代结果的误差
x0 = x;
if(N>=M)
disp('Warning: 迭代次数太多,可能不收敛!');
return;
end
end