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POMATLAB: Differences between .mat versions
 

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    <p>The <a href="http://www.mathworks.com/help/matlab/ref/save.html#inputarg_version" rel="noreferrer">official documentation</a> states the following:</p> <p><img src="https://i.stack.imgur.com/wCcNd.png" alt="enter image description here">. But I have noticed that there are other important differences besides those stated in the table above.</p> <p>For example, saving a cell array with about 6,000 elements that occupies <strong>176 MB</strong> of memory in MATLAB gives me the following results depending on whether I use <strong>-v7</strong> or <strong>-v7.3</strong>:</p> <ul> <li>With <strong>-v7</strong>: File size = <strong>15 MB</strong>, and save &amp; load is <strong>fast</strong>.</li> <li>With <strong>-v7.3</strong>: File size = <strong>400 MB</strong>, and save &amp; load is <em>very</em> <strong>slow</strong> (probably in part because of the large file size).</li> </ul> <p>Has anybody else noticed these differences? </p> <p><strong>Update 1</strong>: As the replies point out, <strong>-v7.3</strong> relies on HDF5 and according to Mathworks, <em>"this format has a significant storage overhead"</em>, although it's not clear if this overhead is really due to the format itself, or to the MATLAB implementation and handling of HDF5 instead.</p> <p><strong>Update 2</strong>: @Andrew Janke points us to <a href="http://mathworks.com/help/pdf_doc/matlab/matfile_format.pdf" rel="noreferrer">this very helpful PDF</a> (which apparently is not available in HTML format on the web). For more details, see the comments in the answer provided by @Amro.</p> <p>This all takes me to the next question: <strong>Are there any alternatives</strong> that combine the best of both worlds (e.g. the efficiency of <strong>-v7</strong> and the ability to deal with very large files of -<strong>v7.3</strong>)?</p>
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    1. COThose interested, check out this recent article: [Improving save performance](http://undocumentedmatlab.com/blog/improving-save-performance/)
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