
Ublas : 
Subject: Re: [ublas] Anybody still there?
From: Sean Reilly (campreilly_at_[hidden])
Date: 20120201 11:03:26
Good to see. It's a nice product.
My interests are more along the lines of extending uBLAS for
vectorized scientific computations. A idea similar to the conceptual
framework that Matlab provides, but in a way that takes full advantage
of C++ expression templates. My take is that this mostly requires an
extension of the basic vector/matrix expression:
 scalar addition: vector +/ scalar, scalar +/ vector
 division of scalar by vector
 limiting functions: max(), min(), floor(), ceil()
 algebraic functions: abs(), abs2(), arg(), sqrt(), copysign()
 trigonometric functions: cos(), cosh(), sin(), sinh(), tan(), tanh()
 inverse trig functions: acos(), acosh(), asin(), asinh(), atan(),
atan2(), atanh()
 exponential functions: exp(), log(), log10(), pow()
So that I can do things like the great circle distance of a collection
of points from an origin (see
http://williams.best.vwh.net/avform.htm#Dist)
boost::numeric::ublas::vector<double> d, lat, lng ;
double lat0, lng0 ;
... fill in values ...
d = 2.0 * asin( sqrt( abs2(
sin( 0.5*(latlat0) ) + cos(lat) * cos(lat0) * abs2( sin(
0.5*(lonlon0)) ) )
) ) ) ;
It seems to me that uBLAS should do a pretty good job of optimizing
this operation, even though it has very little to do with
matrix/vector mathematics.
Question: Why do you include support for multiplication of a
vector/matrix by a scalar, but not addition?
Question: Do you know of a way to overload operator*() to perform the
same function as element_prod()? Basically, and equivalent to the
Matlab operation ".*". Note how "messy" cosine terms in the equation
above becomes when you have to use element_prod() all of the time.
I've tried specializing the existing the implementation of (t * v) [i]
= t * v [i], but I keep screwing it up.
Sean Reilly
On Wed, Feb 1, 2012 at 10:29 AM, David Bellot <david.bellot_at_[hidden]> wrote:
> There has been a few changes and documentation written in fact. A few new
> algorithms has been added like the assignment operators.
>
> It is actively maintained even if in it's current state there is not a lot
> to do.
> In fact, I'm seriously thinking at ...
>
> <flame wars>
>  changing the core library to make it able to be faster, introduce new
> algorithms, and autovectorization
>
>  removing the vector class in favor of a unique matrix class (and vector
> would simply be a onecolumn matrix). That would allow us to simply
> represent column and row vector and unify the computation engine
>
>  be faster than eigen and armadillo: ok that one is gonna be pretty hard
> :D
> </flame wars>
>
> Meanwhile, I'm slowly improving little things... Fortunately, I have been
> using ublas for my job for the last few years.
> But for sure, it needs more love.
>
> On Wed, Feb 1, 2012 at 15:15, Sean Reilly <campreilly_at_[hidden]> wrote:
>>
>> I'm using uBLAS for a big project, and just wanted to see if it is
>> still being actively maintained. It doesn't seem like there have been
>> many changes in the last few years.
>>
>> Sean Reilly
>> _______________________________________________
>> ublas mailing list
>> ublas_at_[hidden]
>> http://lists.boost.org/mailman/listinfo.cgi/ublas
>> Sent to: david.bellot_at_[hidden]
>
>
>
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