[Haskell-cafe] low-cost matrix rank?

Audun Skaugen audunskaugen at gmail.com
Fri Apr 24 14:01:24 UTC 2015

What about dumping the matrix into a C array using the storable instance  
of the linear package's matrices, and then use a foreign-imported svd call  
 from lapack? I don't know whether you can count on lapack being available  
in your systems. The lapack call is very clumsy, requiring lots of pointer  
inputs, but it should be doable in a few lines of code.

The rank is then the number of nonzero singular values, for some  
accuracy-dependent definition of "nonzero".

På Fri, 24 Apr 2015 15:30:23 +0200, skrev Mike Meyer <mwm at mired.org>:

> The bed-and-breakfast isn't to bad, except for needing TH. But it's  
> apparently not being maintained. I've started the process of >replacing  
> the maintainer, but may roll my own instead.
> Thanks,
> Mike
> On Fri, Apr 24, 2015 at 8:27 AM, Dennis J. McWherter, Jr.  
> <dennis at deathbytape.com> wrote:
>> I am not aware of any small library which does just this, but you could  
>> easily roll your own. Though not the most efficient >>method,  
>> implementing gaussian elimination is a straightforward task (you can  
>> even find the backtracking algorithm on google) and >>then you can find  
>> the rank from there.
>> Dennis
>> On Fri, Apr 24, 2015 at 6:50 AM, Mike Meyer <mwm at mired.org> wrote:
>>> My apologies,but my use of "low-cost" was ambiguous.
>>> I meant the cost of having it available - installation, size of the  
>>> package, extra packages brought in, etc. I don't the rank  
>>> >>>calculation to be fast, or even cheap to compute, as it's not used  
>>> very often, and not for very large matrices. I'd rather not >>>have  
>>> the size of the software multiplied by integers in order to get that  
>>> one function.
>>> hmatrix is highly optimized for performance and parallelization, built  
>>> on top of a large C libraries with lots of >>>functionality. Nice to  
>>> have if you're doing any serious work with matrices, but massive  
>>> overkill for what I need.
>>> On Fri, Apr 24, 2015 at 3:13 AM, Alberto Ruiz <aruiz at um.es> wrote:
>>>> Hi Mike,
>>>> If you need a robust numerical computation you can try "rcond" or  
>>>> "rank" from hmatrix. (It is based on the singular values, >>>>I don't  
>>>> know if the cost is low enough for your application.)
>>>> http://en.wikipedia.org/wiki/Rank_%28linear_algebra%29#Computation
>>>> https://hackage.haskell.org/package/hmatrix-
>>>> Alberto
>>>> On 24/04/15 00:34, Mike Meyer wrote:
>>>>> Noticing that diagrams 1.3 has moved from vector-space to linear, I
>>>>> decided to check them both for a function to compute the rank of a
>>>>> matrix. Neither seems to have it.
>>>>> While I'm doing quite a bit of work with 2 and 3-element vectors, the
>>>>> only thing I do with matrices is take their rank, as part of  
>>>>> verifying
>>>>> that the faces of a polyhedron actually make a polyhedron.
>>>>> So I'm looking for a relatively light-weight way of doing so that  
>>>>> will
>>>>> work with a recent (7.8 or 7.10) ghc release. Or maybe getting such a
>>>>> function added to an existing library. Anyone have any suggestions?
>>>>> Thanks,
>>>>> Mike
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Audun Skaugen
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