Dear monks,

please accept my sincere apologies if you find the following question trivial.

Could anyone tell me why a self-made sparse matrix multiplication without PDL is bound to fail, as moritz said? In my opinion, anyone can use twice-nested hashs in order to represent a sparse 2d-matrix: 

$matrix{$row}{$column}=$value

[download]
This doesn't store the zeroes, and multiplication is also straightforward, by looping over appropiate key lists.

I don't see why this solution should be slower than using piddles.

Thank you very much for shedding some light on this issue.

In reply to Why not use a nested hash? by Eckhart
in thread Sparse Matrix Multiplication Problem by neversaint

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.