Why does my script takes longer time to execute than expected?

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University Glasgow 2023-2-27

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评论： University Glasgow 2023-3-6

Hi, I tried to run my matlab script. In the attached file: MBBA5CBPAA_Result.m, I tried to run only the second section:Active dissipation. The computation is supposed to take 11 hours 36 minutes but is still running even after 12 hours. Please is there any way to speed up the running time. The Non_linear1_differentu_MBBA_func1.m and dissipative_elastic_energy_MBBA_fun.m are subroutines (functions), while the MBBA5CBPAA_Result.m is where the run the code.

Your assistance is highly appreciated. Thank you.

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Walter Roberson 2023-2-27

在 MATLAB Online 中打开

@University Glasgow

Your current code in dissipative_elastic_energy_MBBA_func has

for iu=1:length(u)
     for  ixi=1:length(xi)
         [nt,tspan,THETA, V, z, t]= Non_linear1_differentu_MBBA_func1(u(iu), xi(ixi), d, N);

so you are passing in individual u and individual xi values to Non_linear1_differentu_MBBA_func1

But that function has

Xix = xi;
Ui = u;
for Xidx = 1:length(Xix)
    xi = Xix(Xidx);  
    for Uidx = 1:length(Ui)
        u = Ui(Uidx);

so that function is already looping over each xi and u value. You do not need to pass in individual u and xi pairs into Non_linear1_differentu_MBBA_func1 -- you could call

[all_nt, tspan, all_THETA, all_V, all_z, all_t] = Non_linear1_differentu_MBBA_func1(u, xi, d, N);

0r something similar to that, knowing that Non_linear1_differentu_MBBA_func1 is already designed to return data for all of the u xi combinations. You would have to look more carefully at the output values for Non_linear1_differentu_MBBA_func1 to see how it puts the values together.

Perhaps you would want to still loop over individual u elements but process all of the xi elements at the same time.

I would expect that the overhead of calling Non_linear1_differentu_MBBA_func1 length(u) by length(xi) times instead of just once would be only a small portion of the cost of the code. It looks to me as if your major cost is the ode45 call with the timespan that is 20001 elements. It is not obvious to me why you are asking for so many output times.

Walter Roberson 2023-2-28

在 MATLAB Online 中打开

1.06 * 60 / (11*11)
ans = 0.5256
26.7 * 60 / (51*51)
ans = 0.6159

so it is a little slower per iteration as you increase the mesh size, but not greatly so. 20%-ish ?

University Glasgow 2023-3-6

Okay, thank you.

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