Sequences can't be used as uBLAS vectors in some operations

[campreilly]

Because usml::types::seq_vector is missing some functionality, sequences can't be used as uBLAS vectors in some operations. Example from usml::ocean::reflect_loss_rough::reflect_loss()

We'd like to write:

    noalias(*amplitude) = exp( ( -TWO_PI / _sound_speed
            * _wave_height * abs(sin(angle)) )
            * frequencies ) ;

But this generates errors in the form

/usr/local/include/boost/numeric/ublas/vector_expression.hpp: In instantiation of ‘boost::numeric::ublas::vector_reference<const usml::types::seq_vector>’:
/usr/local/include/boost/numeric/ublas/vector_expression.hpp:1222:   instantiated from ‘boost::numeric::ublas::vector_binary_scalar1<const double, usml::types::seq_vector, boost::numeric::ublas::scalar_multiplies<double, double> >’
/home/sreilly/Projects/usml/../usml/ocean/reflect_loss_rough.h:70:   instantiated from here
/usr/local/include/boost/numeric/ublas/vector_expression.hpp:172: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’
/usr/local/include/boost/numeric/ublas/vector_expression.hpp:180: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’
/usr/local/include/boost/numeric/ublas/vector_expression.hpp:204: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’
/usr/local/include/boost/numeric/ublas/vector_expression.hpp:208: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’
/usr/local/include/boost/numeric/ublas/vector_expression.hpp:214: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’
/usr/local/include/boost/numeric/ublas/vector_expression.hpp:234: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’
/usr/local/include/boost/numeric/ublas/vector_expression.hpp:238: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’

So, instead we write:

    noalias(*amplitude) = frequencies ; // copy sequence into vector
    noalias(*amplitude) = exp( ( -TWO_PI / _sound_speed
            * _wave_height * abs(sin(angle)) )
            * (*amplitude) ) ;

[Tibonium]

Should seq_vector be extended to have a non-const iterator calls? Making a seq_vector a true vector class of ublas

On Nov 29, 2014 11:05 AM, Sean Reilly notifications@github.com wrote:

Because usml::types::seq_vector is missing some functionality, sequences can't be used as uBLAS vectors in some operations. Example from usml::ocean::reflect_loss_rough::reflect_loss()

We'd like to write:

noalias(*amplitude) = exp( ( -TWO_PI / _sound_speed
        * _wave_height * abs(sin(angle)) )
        * frequencies ) ;

But this generates errors in the form

/usr/local/include/boost/numeric/ublas/vector_expression.hpp: In instantiation of ‘boost::numeric::ublas::vector_reference’: /usr/local/include/boost/numeric/ublas/vector_expression.hpp:1222: instantiated from ‘boost::numeric::ublas::vector_binary_scalar1<const double, usml::types::seq_vector, boost::numeric::ublas::scalar_multiplies<double, double> >’ /home/sreilly/Projects/usml/../usml/ocean/reflect_loss_rough.h:70: instantiated from here /usr/local/include/boost/numeric/ublas/vector_expression.hpp:172: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’ /usr/local/include/boost/numeric/ublas/vector_expression.hpp:180: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’ /usr/local/include/boost/numeric/ublas/vector_expression.hpp:204: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’ /usr/local/include/boost/numeric/ublas/vector_expression.hpp:208: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’ /usr/local/include/boost/numeric/ublas/vector_expression.hpp:214: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’ /usr/local/include/boost/numeric/ublas/vector_expression.hpp:234: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’ /usr/local/include/boost/numeric/ublas/vector_expression.hpp:238: error: no type named ‘iterator’ in ‘const class usml::types::seq_vector’

So, instead we write:

noalias(*amplitude) = frequencies ; // copy sequence into vector
noalias(*amplitude) = exp( ( -TWO_PI / _sound_speed
        * _wave_height * abs(sin(angle)) )
        * (*amplitude) ) ;

— Reply to this email directly or view it on GitHubhttps://github.com/campreilly/UnderSeaModelingLibrary/issues/66.

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[campreilly]

No. I'd like to find a way to fix this while maintaining the read-only nature of sequences.

[Tibonium]

I do not believe this is possible to solve with the current implementation of seq_vector, based on

"\brief A zero vector of type \c T and a given \c size A zero vector of type \c T and a given \c size. This is a virtual vector in the sense that no memory is allocated for storing the zero values: it still acts like any other vector. However assigning values to it will not change the zero vector into a normal vector. It must first be assigned to another normal vector by any suitable means. Its memory footprint is constant."

Which is the basis for the seq_vector class, "This design uses zero_vector as a model of how to implement a read-only uBLAS vector." As such all sequences are NOT vector_expression/vectors and therefore do not have the iterator defined. Even after adding a typedef iterator does not produce the expected results. I believe that the inheritance and formulation of sequence classes prevent the boost from treating it as a vector in compound statements.

The only workaround that currently exists outside of first assigning, is to create a temporary vector live such as:

noalias(amplitude) = exp( ( -TWO_PI / _sound_speed * _wave_height * abs(sin(angle)) ) \ vector(frequencies.data()) ) ;

[campreilly]

In this case, we aren't actually trying to assign any values to the frequencies vector. I wonder why is doesn't work. Weird. Does using a zero vector in place of the frequencies vector compile?

[Tibonium]

I have figured out how to do it, however, it does require that the seq_vector class be rewritten. I am trying to find a way to adapt it to be usable in usml with minimal changes, if plausible. My prototype sequence class does follow the protected data design as desired with all seq_vectors.