Call of textscan or strfind function takes long time for first time while running in loop [matlab 2020b on linux centos]
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Sanat Kumar Tiwari
am 14 Jul. 2021
Kommentiert: dpb
am 14 Jul. 2021
We are trying to read a file which has repeatedly 9 rows of text followed by 200000 particle trajectories. A piece of code, enough to produce the problem is:
fname = abc.txt;
fid = fopen(fname,'r');
for ii = 1:20
InputText=textscan(fid,'%s',9,'delimiter','\n');
ii
pp = InputText{1};
Nrows = pp{4}
aa =textscan(fid,'%d %d %f %f %f %f', ... % Read data block
'delimiter',',');
end
apparently, to print ii = 1, it takes 10 seconds while rest all calls in loop finish in 1-2 seconds. It clearly indicates that trouble is on first call of textscan and not with subsequent calls.
The same issue is with strfind function if i put in loop.
I checked on matlab and the answers suggest either license issue or graphics issue. I ran matlab with no-desktop and still got the same issue. I checked it with Nvidia and opengl software choice and issue persists.
Kindly help resolving.
1 Kommentar
dpb
am 14 Jul. 2021
InputText=textscan(fid,'%s',9,'delimiter','\n');
ii
pp = InputText{1};
Nrows = pp{4}
looks peculiar -- you read as char() data but then use the content as numeric without a conversion operation.
Akzeptierte Antwort
Walter Roberson
am 14 Jul. 2021
Specify the file encoding when you do the fopen(), or else it will scan the entire file checking to see if any utf8 is present
2 Kommentare
dpb
am 14 Jul. 2021
I'm always forgetting that change in behavior, too...glad your rememberer is better, Walter! :)
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