rand(n,1)

Question

Randall 2019-10-29

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/487940-rand-n-1

回答： Ajay Pattassery 2019-10-31

I gave an exam and figured I'd use rand in a few places to make sure there was no cheating. For question #2 on the exam, I specifically had 6 students solve the equation Ax=b with A=[0 -1 0 -1; -1 0 1 -2; 1 -1 0 1; 0 1 1 0]; and b=rand(4,1). I received exactly 3 different b-vectors from 3 pairs of students that don't talk with each other. In trying to understand the "chances" of this, I found

https://www.mathworks.com/help/matlab/math/why-do-random-numbers-repeat-after-startup.html

which says

"All the random number functions, rand, randn, randi, and randperm, draw values from a shared random number generator. Every time you start MATLAB®, the generator resets itself to the same state. Therefore, a command such as rand(2,2) returns the same result any time you execute it immediately following startup. Also, any script or function that calls the random number functions returns the same result whenever you restart."

I understand that when I open up and run matlab that it will reset the generator to the same state but is it obvious from this or other documentation that this should happen for pairs of people (with different releases and platforms)? A subsequent question had them use rand(3,3) and 6 different matrices were submitted.