Re: More Informed Sort

[David Bateman]

The octave soring class is based on a mergesort and given partially 
sorted lists will be significantly faster than other types of sorts. The 
matlab sorting class is based on quicksort so is better for random 
lists. This being the case just using octave sort function should give 
near optimum performance.

Additionally as the octave sort function is written as a class you can 
easily apply it to sort other types of data in an oct-file. For example 
to sort an octave_idx_type vector and also return the vector of indices 
you can do something like

class
octave_idx_vector_sort
{
public:
 octave_idx_type i;
 octave_idx_type idx;
};

bool
octave_idx_vector_comp (octave_idx_vector_sort* i,
                       octave_idx_vector_sort* j)
{
 return (i->i < j->i);
}

template class octave_sort<octave_idx_vector_sort *>;

int main (void){
...
         OCTAVE_LOCAL_BUFFER (octave_idx_vector_sort *, sidx, n);
         OCTAVE_LOCAL_BUFFER (octave_idx_vector_sort, sidxX, n);

         for (octave_idx_type i = 0; i < n; i++)
       {
         sidx[i] = &sidxX[i];
         sidx[i]->i = lhs_idx.elem(i);
         sidx[i]->idx = i;
       }

         octave_sort<octave_idx_vector_sort *>  sort 
(octave_idx_vector_comp);
         sort.sort (sidx, n);
...
}

Where sidx[i]->i returns the data and sidx[i]->idx returns the list of 
indices..

Regards
David

--
David Bateman                                address@hidden
Motorola Labs - Paris                        +33 1 69 35 48 04 (Ph) 
Parc Les Algorithmes, Commune de St Aubin    +33 6 72 01 06 33 (Mob) 
91193 Gif-Sur-Yvette FRANCE                  +33 1 69 35 77 01 (Fax) 

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