function [X,k,err]=jacobi(A,B,P,delta,max1)
N=length(B);
D=zeros(N);
for i=1:N
D(i,i)=A(i,i);
end
%求出迭代式中的两个参数
Bj=inv(D)*(D-A);
Fj=inv(D)*B;
%迭代过程
for k=1:max1
X=Bj*P+Fj;
if (norm(abs(X-P))<delta)|((norm(abs(X-P))/(norm(abs(X-P))+eps))<delta)
err=norm(abs(X-P));
break
end
P=X;
end