sparsity iterators to Matrix<>

[casadibot]

The vector class has four functions to get iterators:
begin, end, rbegin, rend

each of these has a const version and a non-const version.

The Matrix<> class inherits these iterators, which is good, but should add two more sets of iterators, for rowind and col. The same should be done for CRSSparsity

Created by jaeandersson at: 2011-01-12T14:31:07
Last updated at: 2012-02-27T20:59:00

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Comment 1 by jgillis at 2012-02-27T20:54:21

Conversion to python iterators seems fairly easy to achieve: http://reference-man.blogspot.com/2010/02/easy-python-generators-using-swig.html

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Comment 2 by jgillis at 2012-02-27T20:59:00

A typical use case:

// Loop over rows
for(int i=0; i<ret.size1(); ++i){
// Loop over nonzeros
for(int el=ret.rowind(i); el<ret.rowind(i+1); ++el){
// Get column
int j=ret.col(el);

// Get the nonzero of the dense matrix
int el_dense = j+i*ret.size2();

// Save to mapping
mapping_dense[el_dense] = mapping[el];
}
}

becomes (pseudo-ish code):

// Loop over rows
for (it = ret.NZ()) {
// Get the nonzero of the dense matrix
int el_dense = it->col + (it->row)*ret.size2();

// Save to mapping
mapping_dense[it.dense] = mapping[el];
}

[jaeandersson]

Looks unlikely to ever get implemented. Reopen if needed.