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Bug 1773 - ft_read_header should be made faster
| Status | CLOSED FIXED |
| Reported | 2012-10-09 20:55:00 +0200 |
| Modified | 2012-10-29 13:44:58 +0100 |
| Product: | FieldTrip |
| Component: | realtime |
| Version: | unspecified |
| Hardware: | PC |
| Operating System: | Mac OS |
| Importance: | P3 normal |
| Assigned to: | Robert Oostenveld |
| URL: | |
| Tags: | |
| Depends on: | |
| Blocks: | 738 |
| See also: |
Robert Oostenveld - 2012-10-09 20:55:56 +0200
I am simulating a localhost data stream with sine2ft and a stand-alone buffer. It writes 16 channels at 2000Hz with a blocksize of 512 samples (so ~4x PUT_DAT per second). Then to get a reference measurement I do the following in MATLAB >> tic; for i=1:1000, ft_read_header('buffer://localhost:1972'); end; toc Elapsed time is 8.863868 seconds. So it takes ~8 ms per read operation.
Robert Oostenveld - 2012-10-09 21:02:04 +0200
with "profile on, running the code, profile report", I see that line 101 in ft_read_header takes a considerable amount of time When I change that from if ~exist(filename, 'file') && ~strcmp(ft_filetype(filename), 'fcdc_buffer') && ~strcmp(ft_filetype(filename), 'ctf_shm') && ~strcmp(ft_filetype(filename), 'fcdc_mysql') into if ~strcmp(ft_filetype(filename), 'fcdc_buffer') && ~strcmp(ft_filetype(filename), 'ctf_shm') && ~strcmp(ft_filetype(filename), 'fcdc_mysql') && ~exist(filename, 'file') So I moved the exist call to the end and the check on fcdc_buffer to the begin (using the short-circuited "&&" in the test). Then I try again and get >> tic; for i=1:1000, ft_read_header('buffer://localhost:1972'); end; toc Elapsed time is 1.783376 seconds. so ~2ms per call. I presume this is fast enough for BCI applications. The profiler is really easy to use, so please give it a try next time.
Robert Oostenveld - 2012-10-09 21:02:52 +0200
mbp> svn commit ft_read_header.m Sending ft_read_header.m Transmitting file data . Committed revision 6712.
Robert Oostenveld - 2012-10-09 21:06:41 +0200
I have made the same change to ft_read_data mbp> svn commit ft_read_data.m Sending ft_read_data.m Transmitting file data . Committed revision 6713.