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Subject: Re: [ublas] ublas+multiprecision+lapack
From: Carsten Burgard (cburgard_at_[hidden])
Date: 2016-06-11 07:27:58

Hi Oswin!

Thanks for this quick response.

In that case, we need to investigate other backend options. Efficiency
is not terribly important to us, as our matrices are comparably small
and runtime is not a concern for this part of the code.

If you happen to know of a backend for UBLAS that we could use in
connection with multiprecision types, ideally one that comes with a bit
of documentation and/or usage examples, that would be awesome!

In any case, thanks again for your input!



On 06/11/2016 12:37 PM, Oswin Krause wrote:
> Hi,
> its futile. LAPACK does not know multiprecision types. This would need
> a templated implementation, luckily there are LAWNs showing that it is
> not too hard to implement in an "efficient" manner (as EVs can not be
> computed efficiently at all...)
> On 2016-06-11 11:55, Carsten Burgard wrote:
>> Hi everyone!
>> I've been using the UBLAS matrix library for about a year now, mostly
>> for very simple operations (matrix inversion, condition number). Due to
>> very special requirements, we're using the types from boost
>> multiprecision to achieve higher precision numerics, which works
>> perfectly.
>> Now, we're trying to go one step further and also calculate some
>> eigenvectors (and eigenvalues). As far as I understand, UBLAS does not
>> natively implement any numerics algorithms for these types of
>> operations, but instead relies on bindings to existing matrix libraries
>> like LAPACK.
>> However, it's not clear to me whether this will still work when
>> templated to multiprecision types. So far, I've been unable to come up
>> with a way to make it work (see, e.g., here.
>> Is there some way to make it work, possibly an example showing how it
>> can be done floating around somewhere on the web? Is there some special
>> backend that needs to be used instead of standard LAPACK? Or is this
>> whole endeavour just futile?
>> Regards,
>> Carsten
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>> Sent to: Oswin.Krause_at_[hidden]