function [point,fval] = invDFP(FCN, X, ERROR, Pflag)
fcn=''; x=[]; error=[]; pflag=[];
if nargin==4
fcn=FCN;
x=X;
error=ERROR;
pflag=Pflag;
elseif nargin==3
fcn=FCN;
x=X;
error=ERROR;
pflag=[0,0];
elseif nargin==2
fcn=FCN;
x=X;
error=1e-4;
pflag=[0,0];
else
error('输入参数不足,无法计算.');
end
% 目标函数自变量的个数
N = size(x);
% 初始设置
k = 1;
x(k,:) = x;
squsum = 0.0;
H = eye(N(2));
db = 100;
while db > error
% 调用'invdifference'函数，计算一阶导数，确定初始搜索方向
x_diff(k,:) = invdifference(fcn, x(k,:));
p(k,:) = - H*x_diff(k,:)';
% 调用'invstep'函数，计算在初始搜索方向的最优步长
step = invstep(fcn, x(k,:), p(k,:));
x(k+1,:) = x(k,:) + step*p(k,:);
x_diff(k+1,:) = invdifference(fcn, x(k+1,:));
S = (x(k+1,:)-x(k,:))';
r = (x_diff(k+1,:)-x_diff(k,:))';
x1=(S*S');x2=r'*S;x3=H*r*r'*H;x4=r'*H*r;
dH = (S*S')/(r'*S) - (H*r*r'*H)/(r'*H*r);
H = H + dH;
squsum = 0.0;
for i = 1:N(2)
squsum = squsum + x_diff(k+1,i)^2;
end
db = sqrt(squsum);
k = k+1;
end
% 得极小点及极小值
point = x(k,:);
fval = fcn(point);
for i = 1:k
f(i) = fcn(x(i,:));
end
if pflag(1)==1
invplotx(x,k);
end
if pflag(2)==1
invplotfcn(f,k);
end
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