urlread-function is very slow since R2012b - why?

3 次查看（过去 30 天）
Sven Meister
Sven Meister 2012-11-11
评论： James 2014-1-13
Hi,
I'm using a small piece of code to read out information from about 100 websites by using urlread in its easiest form:
for count = 1:elements
html_str = urlread(['http://www.website.com/page' num2str(count)]);
end
Yesterday I changed my Matlab-version from R2011a to R2012b and was slightly shocked. With the old version the loop took about 20-30 seconds. The new one needs nearly 5 Minutes!
My research quarry that Mathworks has expanded the urlread-function with 3 additional parameters and took some old ones away. http://www.mathworks.de/de/help/matlab/release-notes.html But I do not use any of these parameters, only the naked function. I tried the manual reduction of the 'Timeout' to 0.1, but with no influence.
Are there any ideas, what causes the speed-loss and first of all how I can get my old performance back? Thanks a lot for your assistance!

请先登录，再回答此问题。

采纳的回答

Jan
Jan 2012-11-11
Why do you assume that the problem is caused by Matlab? Do you have the old Matlab still installed? If so, please check if the old version is slower today also.
  5 个评论
显示 3更早的评论
Andreas Goser
Andreas Goser 2012-11-12
Aha - I found the crossposting Jan mentioned on gomatlab.de :-)
Andreas Goser
Andreas Goser 2012-11-13
Looks like you found a solution, can you share what helped? And I found Wni8 IS supported. Seems to be back qualiified: http://www.mathworks.com/support/sysreq/current_release/

请先登录，再进行评论。

更多回答（2 个）

Clemens
Clemens 2013-11-28
  1 个评论
James
James 2014-1-13
Solved my problem too - on testing, urlread2 is around 10 times faster than urlread.

请先登录，再进行评论。

John Hedengren
John Hedengren 2013-11-8
I also noticed this loss in speed that Sven mentioned on some of our lab computers. We were running 2010b and 2012b. The same code would take 2-3 seconds on 2010b and over 5 minutes on 2012b so we naturally used 2010b. We use a web-service architecture in the APMonitor Optimization toolbox so some users switched to APM Python because of the performance decrease. I recently tried a modified version of urlread with just the basic function calls (see below). It seems to hang up when it tries to get a response from the server.
inputStream = urlConnect.getInputStream;
Any suggestions would be greatly appreciated. The code that we are using is online at APMonitor.com. Running test_all.m should run a number of example problems. For some users it is fast but for others it is extremely slow.
function output = urlread_apm(str)
try
if usejava('jvm'),
import com.mathworks.mlwidgets.io.InterruptibleStreamCopier;
% use Java if available
url = java.net.URL(str);
urlConnect = url.openConnection;
timeout = 1000000000;
method = 'GET';
urlConnect.setRequestMethod(upper(method));
urlConnect.setReadTimeout(timeout);
urlConnect.setDoOutput(true);
outputStream = urlConnect.getOutputStream;
outputStream.close;
try
inputStream = urlConnect.getInputStream;
isGood = true;
catch ME
inputStream = urlConnect.getErrorStream;
isGood = false;
if isempty(inputStream)
msg = ME.message;
I = strfind(msg,char([13 10 9]));
if ~isempty(I)
msg = msg(1:I(1)-1);
end
error(msg)
end
end
byteArrayOutputStream = java.io.ByteArrayOutputStream;
isc = InterruptibleStreamCopier.getInterruptibleStreamCopier;
isc.copyStream(inputStream,byteArrayOutputStream);
inputStream.close;
byteArrayOutputStream.close;
output = char(typecast(byteArrayOutputStream.toByteArray','uint8'));
% output = typecast(byteArrayOutputStream.toByteArray','uint8');
else
% urlread is sometimes slower after R2012a
% use only if Java is not available
output = urlread(url);
end
catch Err
output = urlread(url);
end
end

类别

在 Help Center 和 File Exchange 中查找有关 Startup and Shutdown 的更多信息

标签

产品

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by