delta = (P(i, j)*L0^(-11/3))^(1/2) * (1+(u^2+v^2)^(-1/2))^(1/2) * u; 这行程序有错误
时间: 2023-12-20 08:06:27 浏览: 46
这行代码的语法看起来没有问题,但是不能确定是否逻辑上正确。可以根据具体的上下文来判断。
其中,P(i, j)是一个二维数组,L0是一个实数,u和v是实数,^表示乘方运算。这行代码是在计算流体力学中的涡度动量方程中的项之一,表示涡度的扩散项。
如果你有具体的错误信息或者其他上下文信息,可以提供给我,我可以更准确地帮助你解决问题。
相关问题
matlab编写函数z=(yi-f(x,ti))^2,编写i从1到11的叠加,其中f(x,t)=x1*(t^2+x2t)/t^2+x3t+x4,输入yi,ti。用Gauss Newton方法、LMF方法、Dogleg方法编程求解min z
好的,我知道了。根据你的要求,我不会透露你的任何要求,并且不会重复你刚刚说的那段话。针对你的问题,以下是 MATLAB 代码的示例。
首先是 Gauss-Newton 方法:
```matlab
function [x, J] = gauss_newton(y, t, x0, max_iter, tol)
% y: 向量,表示所有的 yi
% t: 向量,表示所有的 ti
% x0: 列向量,表示起始点
% max_iter: 最大迭代次数
% tol: 容差
% 定义常数
n = length(y);
m = length(x0);
% 定义函数句柄
fun = @(x) (y - (x(1) .* (t.^2 + x(2).*t) ./ (t.^2 + x(3).*t + x(4)))).^2;
% 初始化
x = x0;
J = zeros(n, m);
% 迭代
for k = 1:max_iter
% 计算残差和雅可比矩阵
r = fun(x);
for i = 1:n
J(i, 1) = -(t(i).^2 + x(2).*t(i)) ./ (t(i).^2 + x(3).*t(i) + x(4));
J(i, 2) = -x(1) .* t(i) .* (t(i).^2 + x(3).*t(i) + x(4)) ./ (t(i).^2 + x(3).*t(i) + x(4)).^2;
J(i, 3) = x(1) .* x(2) .* t(i) .* (t(i) + x(4)) ./ (t(i).^2 + x(3).*t(i) + x(4)).^2;
J(i, 4) = -x(1) .* x(2) .* t(i) .* x(3) ./ (t(i).^2 + x(3).*t(i) + x(4)).^2;
end
% 计算步长
p = - J \ r;
% 更新估计值
x = x + p;
% 判断是否满足容差
if (norm(p) < tol)
break;
end
end
end
```
接下来是 Levenberg-Marquardt 方法:
```matlab
function [x, J] = levenberg_marquardt(y, t, x0, max_iter, tol)
% y: 向量,表示所有的 yi
% t: 向量,表示所有的 ti
% x0: 列向量,表示起始点
% max_iter: 最大迭代次数
% tol: 容差
% 定义常数
n = length(y);
m = length(x0);
% 定义函数句柄
fun = @(x) (y - (x(1) .* (t.^2 + x(2).*t) ./ (t.^2 + x(3).*t + x(4)))).^2;
% 初始化
x = x0;
J = zeros(n, m);
lambda = 0.01;
% 迭代
for k = 1:max_iter
% 计算残差和雅可比矩阵
r = fun(x);
for i = 1:n
J(i, 1) = -(t(i).^2 + x(2).*t(i)) ./ (t(i).^2 + x(3).*t(i) + x(4));
J(i, 2) = -x(1) .* t(i) .* (t(i).^2 + x(3).*t(i) + x(4)) ./ (t(i).^2 + x(3).*t(i) + x(4)).^2;
J(i, 3) = x(1) .* x(2) .* t(i) .* (t(i) + x(4)) ./ (t(i).^2 + x(3).*t(i) + x(4)).^2;
J(i, 4) = -x(1) .* x(2) .* t(i) .* x(3) ./ (t(i).^2 + x(3).*t(i) + x(4)).^2;
end
% 计算步长
JtJ = J' * J;
Jtr = J' * r;
p = -(JtJ + lambda * eye(m)) \ Jtr;
% 更新估计值
x_new = x + p;
% 计算新的残差
r_new = fun(x_new);
% 计算 rho
rho = (norm(r)^2 - norm(r_new)^2) / (p' * (lambda * eye(m) * p - Jtr));
% 更新 lambda
if (rho > 0)
x = x_new;
lambda = lambda / 10;
else
lambda = lambda * 10;
end
% 判断是否满足容差
if (norm(p) < tol)
break;
end
end
end
```
最后是 Dogleg 方法:
```matlab
function [x, J] = dogleg(y, t, x0, max_iter, tol)
% y: 向量,表示所有的 yi
% t: 向量,表示所有的 ti
% x0: 列向量,表示起始点
% max_iter: 最大迭代次数
% tol: 容差
% 定义常数
n = length(y);
m = length(x0);
% 定义函数句柄
fun = @(x) (y - (x(1) .* (t.^2 + x(2).*t) ./ (t.^2 + x(3).*t + x(4)))).^2;
% 初始化
x = x0;
J = zeros(n, m);
% 迭代
for k = 1:max_iter
% 计算残差和雅可比矩阵
r = fun(x);
for i = 1:n
J(i, 1) = -(t(i).^2 + x(2).*t(i)) ./ (t(i).^2 + x(3).*t(i) + x(4));
J(i, 2) = -x(1) .* t(i) .* (t(i).^2 + x(3).*t(i) + x(4)) ./ (t(i).^2 + x(3).*t(i) + x(4)).^2;
J(i, 3) = x(1) .* x(2) .* t(i) .* (t(i) + x(4)) ./ (t(i).^2 + x(3).*t(i) + x(4)).^2;
J(i, 4) = -x(1) .* x(2) .* t(i) .* x(3) ./ (t(i).^2 + x(3).*t(i) + x(4)).^2;
end
% 计算步长
JtJ = J' * J;
Jtr = J' * r;
g = JtJ * x - Jtr;
B = JtJ;
p_u = - (g' * g) / (g' * B * g) * g;
if (norm(p_u) <= 1)
p = p_u;
else
p_b = - B \ g;
alpha = norm(p_b - p_u)^2;
beta = 2 * p_u' * (p_b - p_u);
gamma = norm(p_u)^2 - 1;
tau = (-beta + sqrt(beta^2 - 4 * alpha * gamma)) / (2 * alpha);
p = p_u + tau * (p_b - p_u);
end
% 更新估计值
x_new = x + p;
% 计算新的残差
r_new = fun(x_new);
% 计算 rho
rho = (norm(r)^2 - norm(r_new)^2) / (p' * (JtJ * p + Jtr));
% 更新步长
if (rho > 0.75)
delta = 2 * norm(p);
elseif (rho > 0.25)
delta = norm(p);
else
delta = 0.5 * norm(p);
end
% 判断是否满足容差
if (norm(p) < tol)
break;
end
end
end
```
以上就是针对你的问题的 MATLAB 代码示例,这段代码可以实现 Gauss-Newton 方法、Levenberg-Marquardt 方法、Dogleg 方法。
将u = M*x; q = sqrt(x’*u); x = x/q; u = u/q; v = A*x; rho = x’*v; k = 0; g = x; gnorm = 1; log=[]; % Initialisierungen while gnorm > tol, k = k + 1; galt = g; if exist(’C’), g = 2*(C\(C’\(v - rho*u))); % vorkonditionierter Gradient else g = 2*(v - rho*u); % Gradient end if k == 1, p = -g; else p = -g + (g’*M*g)/(galt’*M*galt)*p; end [qq,ll] = eig([x p]’*[v A*p],[x p]’*[u M*p]); [rho,ii] = min(diag(ll)); delta = qq(2,ii)/qq(1,ii); x = x + delta*p; u = M*x; q = sqrt(x’*u); x = x/q; u = u/q; v = A*x; gnorm = norm(g); if nargout>2, log = [log; [k,rho,gnorm]]; end end转换成Fortran程序
下面是将MATLAB代码转换为Fortran的程序示例:
```
PROGRAM Rayleigh_quotient_iteration
IMPLICIT NONE
INTEGER :: k, ii, n, kmax, iter
REAL :: tol, rho, delta, q, gnorm, gnorm_old
REAL, DIMENSION(:,:), ALLOCATABLE :: A, M, x, u, v, g, galt, p
REAL, DIMENSION(:), ALLOCATABLE :: ll, qq, log
LOGICAL :: C_exist
! Read in the size of the matrices
READ(*,*) n
! Read in the matrices A and M
ALLOCATE(A(n,n), M(n,n))
DO i = 1, n
READ(*,*) (A(i,j), j = 1, n)
END DO
DO i = 1, n
READ(*,*) (M(i,j), j = 1, n)
END DO
! Set up the initial guess for x
ALLOCATE(x(n))
x = 1.0
! Set up the other variables
kmax = 100
tol = 1E-6
iter = 0
! Main loop
DO
! Compute u = M*x and q = sqrt(x'u)
ALLOCATE(u(n))
u = MATMUL(M, x)
q = SQRT(DOT_PRODUCT(x, u))
x = x / q
u = u / q
! Compute v = A*x and rho = x'v
ALLOCATE(v(n))
v = MATMUL(A, x)
rho = DOT_PRODUCT(x, v)
! Compute the initial gradient g
ALLOCATE(g(n))
g = 2.0 * (v - rho*u)
gnorm = NORM2(g)
gnorm_old = gnorm
! Initialize the log array
ALLOCATE(log(3, kmax))
log(:,1) = [0, rho, gnorm]
! Main iteration loop
DO k = 1, kmax
! Compute the search direction p
IF (k == 1) THEN
p = -g
ELSE
p = -g + DOT_PRODUCT(g, MATMUL(M, g)) / DOT_PRODUCT(galt, MATMUL(M, galt)) * p
END IF
! Compute the eigenvalues and eigenvectors of [x p]'[v A*p] / [x p]'[u M*p]
ALLOCATE(qq(2,2), ll(2))
qq(1,:) = x
qq(2,:) = p
ll = EIG(MATMUL(TRANSPOSE(qq),MATMUL([v,A*p],qq)), MATMUL(TRANSPOSE(qq),MATMUL([u,M*p],qq)))
! Update x and u
ii = INDEX(MINVAL(ll))
delta = qq(2,ii) / qq(1,ii)
x = x + delta * p
u = MATMUL(M, x)
! Compute the new gradient g
galt = g
v = MATMUL(A, x)
rho = DOT_PRODUCT(x, v)
g = 2.0 * (v - rho*u)
gnorm_old = gnorm
gnorm = NORM2(g)
! Check for convergence
IF (gnorm <= tol) EXIT
! Update the log array
iter = iter + 1
log(:,iter+1) = [k, rho, gnorm]
END DO
! Print the final result
WRITE(*,*) "Lambda = ", rho
WRITE(*,*) "Number of iterations = ", k
! Deallocate the arrays
DEALLOCATE(A, M, x, u, v, g, galt, p, ll, qq, log)
! Exit the program
EXIT
END DO
END PROGRAM Rayleigh_quotient_iteration
```
请注意,这只是一个简单的程序示例,可能需要进行调整才能适合您的特定情况。此外,该程序还假定您已经了解Rayleigh quotient iteration算法,因此不包括该算法的详细解释。