function x=fsxsteep(f,e,a,b)
% fsxsteep函數(shù) 最速下降法
% x=fsxsteep(f,e,a,b)為輸入函數(shù) f為函數(shù) e為允許誤差 (a,b)為初始點(diǎn);

% fsx TJPU 2008.6.15

x1=a;x2=b;
Q=fsxhesse(f,x1,x2);
x0=[x1 x2]';
fx1=diff(f,'x1'); %對(duì)x1求偏導(dǎo)數(shù)
fx2=diff(f,'x2'); %對(duì)x2求偏導(dǎo)數(shù)
g=[fx1 fx2]'; %梯度
g1=subs(g); %把符號(hào)變量轉(zhuǎn)為數(shù)值
d=-g1;
while (abs(norm(g1))>=e)
	t=(-d)'*d/((-d)'*Q*d);t=(-d)'*d/((-d)'*Q*d); %求搜索方向
	x0=x0-t*g1; %搜索到的點(diǎn)
	v=x0;
	a=[1 0]*x0;
	b=[0 1]*x0;
	x1=a;
	x2=b;
	g1=subs(g);
	d=-g1;
	end;
x=v;