Why the external dos command/program is so slow in 64 bit window?

11 Ansichten (letzte 30 Tage)
Zhi
Zhi am 22 Feb. 2011
Bearbeitet: Jan am 3 Mai 2017
Hi,
I try executing some external commands/programs in Matlab (R2010a, 64bit) but they are very slow. Here is an example: Matlab program: disp('Test external command in Matlab');
for i = 1:5 tic system('cd .'); toc end
Results: Test external command in Matlab Elapsed time is 7.136996 seconds. Elapsed time is 6.094630 seconds. Elapsed time is 5.574957 seconds. Elapsed time is 6.235473 seconds. Elapsed time is 5.973438 seconds.
My computer is Dell Optiplex 980, Windows 7. I have not met the same problem in Linux or 32bit Matlab.

Antworten (4)

Jan
Jan am 22 Feb. 2011
Bearbeitet: Jan am 3 Mai 2017
This can depend on "cd .". If the current directory contains 7000 files and is on a network drive connected by a 100MBit ethernet, 6 seconds are not really surprising.

the cyclist
the cyclist am 22 Feb. 2011
I am using R2010b on a 64-bit Mac, and I do not see that behavior. My elapsed times are on the order of milliseconds.

Aviv Rosenberg
Aviv Rosenberg am 31 Okt. 2016
Bearbeitet: Walter Roberson am 31 Okt. 2016
Try this:
Haven't tested on windows, but it really speeds up my workflow on OSX.
  1 Kommentar
Walter Roberson
Walter Roberson am 31 Okt. 2016
I notice that the source does
pb.redirectErrorStream(true);
I am wondering if that affects explicit I/O redirection the user may have given on the command line, such as if the command were
someCommand SomeArguments 2>SomeOutputFile
because the user wanted stderr to go to a file?

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Xiangrui Li
Xiangrui Li am 3 Mai 2017
I observed the slowness for both win32 and win64. I just posted a question why redirecting the output to a file improve the performance. It is strange that, even if there is no output, redirecting still makes it faster.
tic, for i = 1:5, system('cd .'); end; toc
Elapsed time is 0.627796 seconds.
tic, for i = 1:5, system('cd . >myFile'); end; toc
Elapsed time is 0.111956 seconds.

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