Comments on: Improving fwrite performance

By: Michelle Kline

Michelle Kline — Wed, 17 May 2023 18:25:24 +0000

*edit*
tip about fopen(), not about fwrite(). ‘Wb’ vs. ‘wb’

By: Michelle Kline

Michelle Kline — Wed, 17 May 2023 18:22:56 +0000

Thank you, Yair! With this previously-unknown-to-me tip about fwrite() performance, you have saved me literally hours of processing time.
Michelle Kline
Department of Radiology and Imaging Research
University of Utah

By: Kerim

Kerim — Sun, 30 Sep 2018 20:03:05 +0000

Very surprising deatail, thank you.
But it’s strange that you didn’t mention a possibility to improve read/write perfomance by adjusting Java. Is that real?

By: Joe V

Joe V — Fri, 01 May 2015 15:18:09 +0000

On a related note: When reading binary files, don't use fseek inside a loop if you can avoid it -- it's very slow. In almost all cases I've tried, it's faster to do

fread(fid, N, '*uint8');

and throw away the result than to do

fseek(fid, N, 'cof');

(although, of course, you can't move backwards in a file using fread, so you're stuck with fseek in that case). This seems to be a limitation of the fseek function in the C library, and it can be especially egregious on network drives. In general, when doing binary file I/O, touch the file as few times as possible. Reading or writing the entire file in one go is fastest. Make use of fread's (and fwrite's) skip parameter when possible. When performance is truly critical, read the data into memory as a uint8 array and parse it yourself using typecast, rather than relying on fread to do the parsing for you. It can be complicated and tricky and error-prone, but it's tons faster.

By: Explicit multi-threading in Matlab – part 1 | Undocumented Matlab

Explicit multi-threading in Matlab – part 1 | Undocumented Matlab — Wed, 19 Feb 2014 20:18:29 +0000

[…] slow for our specific needs. We could perhaps improve it a bit with some fancy tricks for save or fwrite. But let’s take a different approach today, using multi-threading:Using Java threadsMatlab […]

By: Anonymous

Anonymous — Fri, 22 Nov 2013 09:37:59 +0000

Just wonderful! As usual 🙂 I’m very likely to start teaching this in my Matlab classes…

By: Yair Altman

Yair Altman — Wed, 29 May 2013 19:47:54 +0000

In reply to Isaac Stoddard. @Isaac - I first posted statusbar over 6 years ago, in April 2007... Thanks for the coffee :-)

By: Isaac Stoddard

Isaac Stoddard — Wed, 29 May 2013 19:28:18 +0000

I went through this tuning effort at my previous job about 4 years ago, in 2007b era.
I would have wished for the statusbar. (Or had you published it to the software library @ TMW?)

Thanks for the blog, and enjoy a cup of coffee!

By: Jan Simon

Jan Simon — Wed, 22 May 2013 21:33:19 +0000

Thanks to explaining this feature.
There has been a ‘b’ flag for the permissions in FOPEN in Matlab 5.3, but it has been removed from the documentation for higher versions. Now a missing ‘t’ is enough to trigger the binary mode.

It is a pleasure to remind you, Yair, that you use an undocumented feature.

By: Improving save performance | Undocumented Matlab

Improving save performance | Undocumented Matlab — Wed, 08 May 2013 19:44:36 +0000

[…] Two weeks ago I posted an article about improving fwrite’s performance […]