profiler causing severe slowdown

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alon
alon 2011-7-5
Hey all! I've encounter a very odd problem: Suddenly, turning on the profiler causes an unbearable slowdown - even the most simple function hardly returns. * Turning the profiler off returns matlab back to life. * killing matlab and loading it again didn't solve the problem.
Any idea what to do or where to look at??
thanx in advance..
  2 个评论
Robert Cumming
Robert Cumming 2011-7-5
show your example function you mention below
and which version/platform of matlab your using
alon
alon 2011-7-7
The phenomena appeared regardless to the function..
somehow things got back to normal...

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回答（2 个）

C.J. Harris
C.J. Harris 2011-7-5
The Profiler will slow your system down. Only turn it on when you really need it. There is no way to avoid this slow-down.
  1 个评论
alon
alon 2011-7-5
First of all, thank u for responding.
I know the profiler should make the program run slower..yet I encounter an unusual slowdown.. for example: a function which runs without the profiler for 0.01 sec, would take minutes with the profiler..that's defintily a bug!

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Jan
Jan 2011-7-6
This is not a bug. Matlab's JIT can accelerate e.g. FOR loops substantially, but it reorders the calculations. This conclicts with the profiling and in consequence the JIT is disabled, if the profiler runs.
The same happens, if the debugger is enabled , e.g. by setting some breaks points. Example code: http://www.mathworks.com/matlabcentral/answers/8461-double-summation-with-vectorized-loops. This is 100 times faster without break points under Matlab 2009a.
Of course this can reduce the meaning of the profiling results. Therefore some TIC TOCs are often more useful.
  2 个评论
alon
alon 2011-7-7
That a good explenation but I think there was something beyond that... somehow things got back to normal state (I really don't know how?).
thank you for replying anyway!
Jan
Jan 2011-7-7
"Things got back to normal state" is very vague. can you explain the problems with any details?

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