GSoC 2012 Proposal: Continued Work on a D Linear Algebra library (SciD - std.linalg)

[Cristi Cobzarenco]

Unfortunately, my proposal was not picked up this year. I might try to work
on these ideas this summer anyway so I would still be very much interested
in ideas and feedback, but I will probably have much less time if I'll be
working somewhere else.

---
Cristi Cobzarenco
BSc in Artificial Intelligence and Computer Science
University of Edinburgh
Profile: http://www.google.com/profiles/cristi.cobzarenco



On 10 April 2012 12:31, Cristi Cobzarenco <cristi.cobzarenco at gmail.com>wrote:

> Timon is, of course, right. I got a bit confused when trying to simplify
> in a hurry. What I meant was actually something like this:
>
> ops.d:
> import std.stdio;
>
> int sum( T )( T mat ){
>  writeln("ops.sum");
> // return reduce!"a+b"( 0, mat );
>  return 1;
> }
>
> int numelems( T )( T mat ) {
> // return mat.rows * mat.columns;
>  return 1;
> }
>
> int mean( T )( T mat ) {
> return sum( mat ) / numelems( mat );
> }
>
> diagonal.d:
> import ops;
> import std.stdio;
>
> struct DiagonalMatrix {
>  }
>
> int sum( T : DiagonalMatrix )( T mat ) {
> writeln( "diagonal.sum" );
> // return reduce!"a+b"( 0, mat.diagonal() );
>  return 1;
> }
>
> main.d:
> import ops;
> import diagonal;
>
> void main() {
>  DiagonalMatrix mat;
> sum( mat );   // this will not compile, but if removed mean
>  mean( mat ); // will use ops.sum, not diagonal.sum anyway
> }
>
> The first problem could, in theory, be fixed using a member flag,
> something like enum specializedSum = true; and ops.sum could be redefined
> as: int sum( T )( T mat ) if( !T.specializedSum ) {}. But in this case
> mean() would still try to use  ops.sum which will fail. All of this can be
> easily fixed by providing member functions, and having the free functions
> call the member ones when they exist.
>
> ---
> Cristi Cobzarenco
> BSc in Artificial Intelligence and Computer Science
> University of Edinburgh
> Profile: http://www.google.com/profiles/cristi.cobzarenco
>
>
>
> On 10 April 2012 10:35, Timon Gehr <timon.gehr at gmx.ch> wrote:
>
>> On 04/10/2012 03:24 AM, Cristi Cobzarenco wrote:
>>
>>> Thanks for the suggestions!
>>>
>>> I don't think UFCS would help us. Our problem is that we can't do this:
>>> triangular.d:
>>>   struct TriangularMatrix {
>>>
>>>   }
>>>
>>>   void sum( T )( T x ) if( is( T : TriangularMatrix ) ) {
>>>
>>>   }
>>>
>>> diagonal.d:
>>>   struct DiagonalMatrix {
>>>
>>>   }
>>>
>>>   void sum( T )( T x ) if( is( T : DiagonalMatrix ) ) {
>>>   }
>>>
>>> main.d:
>>> import diagonal;
>>> import triangular;
>>>
>>> void bar() {
>>>    TriangularMatrix a;
>>>    Diagonal b;
>>>    sum( a );  // this does not compile because sum() is ambiguous
>>>    sum( b );  // nor does this
>>> }
>>>
>>
>> There are no ambiguities in that example, and if ambiguities occur, they
>> can always be fixed manually.
>>
>>
>>> This, AFAIK, is deliberate to avoid name hijacking - ADL in C++ had its
>>> share of criticism. I doubt we will ever get this behaviour in D and
>>> that is perhaps a good thing. I may have misunderstood UFCS though - or
>>> what you meant by making non-member function calls look nicer - please
>>> correct me if that's the case.
>>>
>>> Don't worry about long names, t() is already the way transposition is
>>> defined SciD. Moreover, it's a property so you can actually do "a.t * a"
>>> - convenience galore. I'm also considering of creating a submodule like
>>> std.linalg.short which defines aliases with short names for types and
>>> free functions - this will allow particularly numerics-heavy functions
>>> to be written more compactly. I'm not entirely sure it would be a good
>>> idea though as it may sacrifice readability where it's most needed.
>>>
>>> ---
>>> Cristi Cobzarenco
>>> BSc in Artificial Intelligence and Computer Science
>>> University of Edinburgh
>>> Profile: http://www.google.com/**profiles/cristi.cobzarenco<http://www.google.com/profiles/cristi.cobzarenco>
>>>
>>>
>> If you change 'Diagonal' to 'DiagonalMatrix', this compiles fine.
>>
>>
>
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