save v7 vs v7.3 - compression is in which one?

Matlab version: 7.11.0.584 (R2010b)

I have a dataset ~68MB in size. Name Size Bytes Class Attributes

datads      299558x21            68295294  dataset

If I save it using -v7 switch, it takes ~12MB on disk. If I save it using -v7.3 switch, it takes ~125MB on disk. Everything I have read suggests v7.3 does compression but v7 doesn't. So these results don't make sense to me. Am I missing something?

Answer 1

[Shashank Prasanna]

matal, v7.3 uses hdf5 format, which offers several advantages over older format. It allows for files larger than 2 gb as well as partial read from the file.

However this comes with a downside, which is a larger chunkier header which allows for all these awesome features. Therefore it is quite expected taht the v7.3 be bigger than an equivalent v7.0

Also this information is present in the documentation here:

http://www.mathworks.com/help/matlab/import_export/mat-file-versions.html