完成斐波那契法和黄金分割法的MATLAB编程与调试; (2)使用斐波那契法和黄金分割法分别求解下述问题minf(x)=x^2-2x+1 ,初始区间为[-1,2],精度ε等于10^(-4)
时间: 2024-10-19 15:02:22 浏览: 76
斐波那契搜索法是一种优化的二分查找算法,而黄金分割法则是寻找最优点的一种数值方法。在MATLAB中,我们可以编写函数来实现这两种方法并求解给定的问题。
首先,我们需要创建一个函数`fib_search_min(f, a, b, epsilon)`来实现斐波那契搜索法。斐波那契搜索需要递归地计算两个子区间的长度,直到满足精度要求。以下是简化的斐波那契搜索示例:
```matlab
function [x, min_val] = fib_search_min(f, a, b, epsilon)
% 初始化斐波那契数列
f0 = 0; f1 = 1;
while abs(f1 - (a + b)) > epsilon * (b - a)
mid = a + (f1 * (b - a)) / (f0 + f1);
if f(mid) < 0
b = mid;
else
a = mid;
end
temp = f0;
f0 = f1;
f1 = temp;
end
x = a;
min_val = f(a);
end
```
对于黄金分割法(也称作割线搜索),我们可以编写一个类似`golden_section_min(f, a, b, epsilon)`的函数。黄金分割比例约为(1 + sqrt(5))/2,我们会在这个比例处评估函数值并更新搜索区间。这里是一个简化版的黄金分割搜索示例:
```matlab
function [x, min_val] = golden_section_min(f, a, b, epsilon)
phi = (1 + sqrt(5)) / 2; % 黄金分割比例
c = a + phi * (b - a); % 右侧切割点
while abs(b - a) > epsilon
if f(a) <= f(c)
b = c;
c = a + phi * (b - a);
else
a = c;
end
end
x = (a + b) / 2; % 最优解
min_val = f(x);
end
```
现在你可以使用这两个函数来解决minf(x)的问题:
```matlab
fun = @(x) x.^2 - 2*x + 1; % 定义目标函数
[~, min_val_fib] = fib_search_min(fun, -1, 2, 1e-4);
[~, min_val_golden] = golden_section_min(fun, -1, 2, 1e-4);
fprintf('Minimum value using Fibonacci search: %.4f\n', min_val_fib);
fprintf('Minimum value using Golden section search: %.4f\n', min_val_golden);
```
运行此代码后,你将得到在指定精度下的斐波那契搜索法和黄金分割法找到的最小值。
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