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Maria on 9 Aug 2024 at 23:37
Edited: Maria about 12 hours ago
- myData.mat
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Hello,
I am encountering an error in MATLAB when using the find function in my code. The error message is:
Error using find Incorrect number or types of inputs or outputs for function 'find'.
The error occurs in the following function:
load(MyData.m)
function SNR_matrix = Compute_SNR(N, numNodes, Devices,A,zeta_m_n,h0, distances,alpha,RIS_elements,arg1,arg2,Theta_node,P_v,Noise_up)
% SNR_matrix = zeros(N, numNodes, Devices);
SNR_matrix = optimexpr(N, numNodes, Devices);
for v = 1:Devices
for sb = 1:N
for node = 1:numNodes
% Find the assigned node for subtask sb of vehicle v
assigned_node = find(A(sb, :, v), 1);
% Find the covering UAV for the vehicle
covering_uav = find(zeta_m_n(v, :), 1);
if assigned_node == covering_uav
% Direct communication
SNR = sqrt(h0 * distances(v, covering_uav)^(-alpha));
SNR_matrix(sb, assigned_node, v) = (P_v*norm(SNR)^2)/Noise_up;
else
% Indirect communication through RIS
% Extract channel gain from vehicle to covering UAV
channel_gains_vehicle_to_covering = zeros(RIS_elements, 1);
for k = 1:RIS_elements
channel_gains_vehicle_to_covering(k) = arg1(v, covering_uav, k);
end
% Extract channel gain from covering UAV to assigned node
arg2_covering_to_assigned = zeros(RIS_elements, 1);
for k = 1:RIS_elements
arg2_covering_to_assigned(k) = arg2(covering_uav, assigned_node, k);
end
h_m_to_n_prime_RIS_phase_shifted = Theta_node{covering_uav} * channel_gains_vehicle_to_covering;
effective_channel = h_m_to_n_prime_RIS_phase_shifted .* arg2_covering_to_assigned;
effective_power = norm(effective_channel)^2;
% Calculate SNR
SNR = P_v * effective_power / Noise_up;
SNR_matrix(sb, assigned_node, v) = SNR;
end
end
end
end
end
and ''A'' is my optimization variable
A = optimvar('A', N, NumNodes, Devices, 'Type', 'integer', 'LowerBound', 0, 'UpperBound', 1);
Unrecognized function or variable 'N'.
How can I resolve this error? I have used fcn2optimexpr but the SNR expression becomes non-linear.
Is there a solution to avoid using find and keep the SNR linear?
Any Help will be appreciated.
Thanks in advance!
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Torsten on 9 Aug 2024 at 23:59
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Edited: Torsten on 10 Aug 2024 at 0:01
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How do you use "Compute_SNR" in your code ?
Somehow like
SNR_matrix = fcn2optimexpr(@Compute_SNR,K, N, M, A, z,...)
after defining all the inputs for the function ?
Maria on 10 Aug 2024 at 0:25
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Thank you for responding me.
Just i used a simple call
SNR_matrix = Compute_SNR(K, N, M, A, z,...);
Torsten on 10 Aug 2024 at 10:11
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That's not possible. You must define a function that can be evaluated using optimization variables - thus you must define the SNR_matrix as output of a fcn2optimexpr.
Maria on 10 Aug 2024 at 10:32
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Thank u again.
Yes this time i didn't get the same error, should i apply it for each function that contains my optimization variable A??
Torsten on 10 Aug 2024 at 13:25
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Edited: Torsten on 10 Aug 2024 at 13:43
If you have a function with optimization variables as input and there are operations/functions within this function that cannot be applied to optimization variables (like "find" in the case posted), you have to use "fcn2optimexpr". I think @Walter Roberson gave you a link where the possible operations on optimization variables (without using "fcn2optimexpr") are listed.
Maria on 10 Aug 2024 at 16:34
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yes, i understand now. Thank you very much.
Maria on 10 Aug 2024 at 19:17
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Hello @Torsten
Could you please help me to solve this issue.
I need to linearize some constraints to use the linprog solver. The problem involves constraints with max functions and products of variables, which introduce nonlinearity.
Here is a portion of my code where I define the variables and constraints:
T_wait = optimvar('T_wait', K, N, M);
T_cmpl = optimvar('T_cmpl', K, N, M);
% Auxiliary variable for max function
z = optimvar('z', K, N, M);
% Define constraints
for m = 1:M
for n = 1:K
for k = 1:N
% Non-negativity constraint
prob.Constraints.(['constr_wait_nonneg_' num2str(m) '_' num2str(n) '_' num2str(k)]) = T_wait(n, k, m) >= 0;
% Constraints for max function
prob.Constraints.(['constr_wait_max_' num2str(m) '_' num2str(n) '_' num2str(k)]) = T_wait(n, k, m) >= z(n, k, m);
prob.Constraints.(['constr_wait_zero_' num2str(m) '_' num2str(n) '_' num2str(k)]) = z(n, k, m) >= 0;
% Constraints for nested max
for k_prime = 1:N
if k ~= k_prime
% Ensure consistent dimensions
prob.Constraints.(['constr_wait_inner_' num2str(m) '_' num2str(n) '_' num2str(k) '_' num2str(k_prime)]) = ...
z(n, k, m) >= o(k_prime, k, m) * T_cmpl(n, k_prime, m) - uplink_time(n, k, m);
end
end
% Constraint: T_cmpl = T_end + T_wait
prob.Constraints.(['constr_cmpl_' num2str(m) '_' num2str(n) '_' num2str(k)]) = ...
T_cmpl(n, k, m) == End_time(n, k, m) + T_wait(n, k, m);
end
end
end
this is the error
Error using optim.problemdef.OptimizationProblem/solve
Unable to perform assignment because the left and right sides have a different number of elements.
Error in Solve_Linear_Problem (line 253)
[sol, fval, exitflag, output] = solve(prob);
Caused by:
Failure in initial user-supplied nonlinear constraint function evaluation
Torsten on 11 Aug 2024 at 0:47
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Edited: Torsten on 11 Aug 2024 at 12:10
I doubt that the error message stems from the part of the code you posted.
And I wonder why you make life difficult for yourself: you relate constraint (m,n,k) with array index (n,k,m). Doesn't it confuse you ?
Maria on 11 Aug 2024 at 11:23
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A already adjust it. Thank you for your response.
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Answers (1)
Walter Roberson on 10 Aug 2024 at 0:03
find() is not a supported operation on optimization variables.
https://www.mathworks.com/help/optim/ug/supported-operations-on-optimization-variables-expressions.html
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