What did they change to 'fread' on 2020a?

The left is 2020a, and the right is 2019a.

As the picture says, it takes significant longer time to execute and sometime it returns different resutls.

Answer 1

[Walter Roberson]

https://www.mathworks.com/help/matlab/release-notes.html?category=data-import-export&rntext=&startrelease=R2020a&endrelease=R2020a&groupby=release&sortby=descending&searchHighlight=

File I/O functions, such as fscanf and fprintf, use automatic character set detection and UTF-8 encoding by default

Behavior change

As of R2020a, character-oriented file I/O functions such as fscanf, fgets, and fgetl trigger automatic character set detection when reading a file that was opened using fopen without a specified encoding.

Similarly, fprintf defaults to using UTF-8 encoding when writing a file that was opened using fopen without a specified encoding

You probably have a large file, and fread() is having to scan through a lot of the file to try to figure out what the character encoding is.

I would suggest that better code for you would be

beg4c = fread(fid, [1 4], 'uint8=>char');

[Y. Li]

Thank you very much!!

Answer 2

[Paul Dankoski]

According to release notes, 2020a, Update 4 is also an option.

https://www.mathworks.com/support/bugreports/details/2254872