Commands faster in one line

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Patrick
Patrick 2014-7-2
评论： dpb 2014-7-2
When I run basic arithmetic, and simple memory allocation tasks in the command window (say matrix multiplication and variable assignment, why is it so much faster to run all the statements in a single line separated by semicolons rather than multiple line with a single tsatement on each? Example:
tic;A = rand(5);B = rand(5);C = A*B;toc
Elapsed time is 0.000039 seconds.
>> tic;
A = rand(5);
B = rand(5);
C = A*B;
toc
Elapsed time is 0.014997 seconds.

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dpb
dpb 2014-7-2
Because at the command line each line is parsed and the JIT compiler/optimizer is pretty much disabled. In an m-file, the file is parsed and then executed.
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Patrick
Patrick 2014-7-2
Ah, so parsing is the rate limiting step here? whereas in an m file, the whole thing is only parsed once, so it doesn't suffer from this same effect?

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