C++ Question

[Quentin H. Spencer]

Hello all,

I have been writing some functions in C that use the octave ComplexSVD 
class, and I'm having trouble understanding some strange behavior. 
Initially I wrote the function with the following syntax:
        
        ComplexSVD svd;
        svd = ComplexSVD( matrix , SVD::std);
        ComplexMatrix U = svd.left_singular_matrix();

Later I changed the syntax to the following (which mirrors the syntax 
used in svd.cc).

        ComplexSVD svd( matrix , SVD::std);
        ComplexMatrix U = svd.left_singular_matrix();

When using the first syntax, the function would usually return properly 
the first time, but subsequent runnings of my C++ function (and 
sometimes even octave's builtin svd function) often resulted in the 
following:

error: ComplexSVD: U not computed because type == SVD::sigma_only

This is usally followed by a segmentation fault. There could be some 
technicality about C++ that I don't understand here, but I don't see the 
different between these two implementations. Can anyone enlighten me?

Quentin Spencer



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