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Ublas : |
Subject: Re: [ublas] Fix conversion from integer to char
From: Nasos Iliopoulos (nasos_i_at_[hidden])
Date: 2016-01-05 11:28:07
Nice,
The second solution that replaces the general value_type with specific
value_types seems the correct one to me and how it should have been
implemented in the first place.
-Nasos
On 01/05/2016 09:37 AM, Joaquim Duran Comas wrote:
> Nasos,
>
> > In line 850 I see:
> > index( ) - it.index()
>
> The error is referring the branch
> https://github.com/jdurancomas/ublas/tree/warning_promoted_types.
>
> > The change you propose may have far reaching consequences. It would be preferable to find
> another way around it, but I am afraid we may need to mess with the
> type definitions of the iterators.
>
> Yes, there is another option. As the definitions of value_type in E1,
> E2 could be different of value_type definitions in vector_binary so
> the local variables that stores values of E1 or E2 should be defined
> as E1::value_type or E2:value_type. Review the commit
> https://github.com/jdurancomas/ublas/commit/bc211a890595790c421055cc47d5c3be160183f7.
>
>
> > Can you please check, that promote_type<char, char>::promote_type is
> an int (as well as the unsigned char, short, unsigned short), after
> applying this change?
>
> No, the change was introduced to force that when two operands of the
> same type was promoted then the promoted type was the same as the
> original one. That is:
>
> promote_type<char, char>::promote_type is char
> promote_type<short, short>::promote_type is short
> .....
>
> Thanks and Best Regards,
> Joaquim Duran
>
>
> 2016-01-04 16:09 GMT+01:00 Nasos Iliopoulos <nasos_i_at_[hidden]
> <mailto:nasos_i_at_[hidden]>>:
>
> Joaquim,
>
> In line 850 I see:
> index( ) - it.index()
>
> Based on the line numbers of the warning text, I cannot trace how
> the difference operator is called or how the promote_type is
> called in the vector_expression.hpp in ublas/develop for the
> particular case.
>
> The change you propose may have far reaching consequences. It
> would be preferable to find another way around it, but I am afraid
> we may need to mess with the type definitions of the iterators.
>
> Can you please check, that promote_type<char, char>::promote_type
> is an int (as well as the unsigned char, short, unsigned short),
> after applying this change?
>
>
> In any case I think there is an issue with the promote_traits that
> are trying to deal with both cases of numerical essence (like as
> elements of a matrix) and size_types.
> In the numerical sense the promote_traits should be able to deal with:
> 1. Subtracting two unsigned integral types should return the
> proper result (i.e. a signed value)
> 2. The promoted type should be able to hold the full range of the
> unpromotted types
>
> No. 2 cannot be satisfied in general (for example for the case of
> unsigned ints, unless an 128-bit is used as the promotion type).
> This is reflected by the choice that the unsigned int promotions
> is also an unsigned int instead of just an int.
>
> -Nasos
>
>
>
> On 01/03/2016 08:43 PM, Joaquim Duran Comas wrote:
>> Hello,
>>
>> I'm trying to fix a warning that it is shown when the test
>> test_matrix_vector is compiled with mscv with all warnings
>> enabled. The text of the warning is the following:
>>
>> *<warning text>*
>> c:\Users\qduran\Documents\development\modular-boost\boost/numeric/ublas/vector_expression.hpp(850)
>> : warning C4244: 'argument' : conversion from 'int' to 'const
>> char', possible loss of data
>> c:\Users\qduran\Documents\development\modular-boost\boost/numeric/ublas/vector_expression.hpp(813)
>> : while compiling class template member function 'int
>> boost::numeric::ublas::vector_binary<E1,E2,F>::const_iterator::dereference(boost::numeric::ublas::sparse_bidirectional_iterator_tag)
>> const'
>> with
>> [
>> E1=boost::numeric::ublas::matrix_column<boost::numeric::ublas::mapped_matrix<char,boost::numeric::ublas::row_major,boost::numeric::ublas::map_std<size_t,char,std::allocator<std::pair<const
>> size_t,char>>>>>
>> ,
>> E2=boost::numeric::ublas::vector<value_type,boost::numeric::ublas::unbounded_array<value_type,std::allocator<char>>>
>> , F=boost::numeric::ublas::scalar_minus<char,value_type>
>> ]
>> c:\Users\qduran\Documents\development\modular-boost\boost/numeric/ublas/vector_expression.hpp(884)
>> : see reference to function template instantiation 'int
>> boost::numeric::ublas::vector_binary<E1,E2,F>::const_iterator::dereference(boost::numeric::ublas::sparse_bidirectional_iterator_tag)
>> const' being compiled
>> with
>> [
>> E1=boost::numeric::ublas::matrix_column<boost::numeric::ublas::mapped_matrix<char,boost::numeric::ublas::row_major,boost::numeric::ublas::map_std<size_t,char,std::allocator<std::pair<const
>> size_t,char>>>>>
>> ,
>> E2=boost::numeric::ublas::vector<value_type,boost::numeric::ublas::unbounded_array<value_type,std::allocator<char>>>
>> , F=boost::numeric::ublas::scalar_minus<char,value_type>
>> ]
>> c:\Users\qduran\Documents\development\modular-boost\boost/numeric/ublas/vector_expression.hpp(1538)
>> : see reference to class template instantiation
>> 'boost::numeric::ublas::vector_binary<E1,E2,F>::const_iterator'
>> being compiled
>> with
>> [
>> E1=boost::numeric::ublas::matrix_column<boost::numeric::ublas::mapped_matrix<char,boost::numeric::ublas::row_major,boost::numeric::ublas::map_std<size_t,char,std::allocator<std::pair<const
>> size_t,char>>>>>
>> ,
>> E2=boost::numeric::ublas::vector<value_type,boost::numeric::ublas::unbounded_array<value_type,std::allocator<char>>>
>> , F=boost::numeric::ublas::scalar_minus<char,value_type>
>> ]
>> c:\Users\qduran\Documents\development\modular-boost\boost/numeric/ublas/vector_expression.hpp(1647)
>> : see reference to class template instantiation
>> 'boost::numeric::ublas::vector_scalar_unary<E,F>' being compiled
>> with
>> [
>> E=boost::numeric::ublas::vector_binary<boost::numeric::ublas::matrix_column<boost::numeric::ublas::mapped_matrix<char,boost::numeric::ublas::row_major,boost::numeric::ublas::map_std<size_t,char,std::allocator<std::pair<constsize_t,char>>>>>,boost::numeric::ublas::vector<value_type,boost::numeric::ublas::unbounded_array<value_type,std::allocator<char>>>,boost::numeric::ublas::scalar_minus<char,value_type>>
>> ,
>> F=boost::numeric::ublas::vector_norm_inf<boost::numeric::ublas::vector_binary<boost::numeric::ublas::matrix_column<boost::numeric::ublas::mapped_matrix<char,boost::numeric::ublas::row_major,boost::numeric::ublas::map_std<size_t,char,std::allocator<std::pair<constsize_t,char>>>>>,boost::numeric::ublas::vector<value_type,boost::numeric::ublas::unbounded_array<value_type,std::allocator<char>>>,boost::numeric::ublas::scalar_minus<char,value_type>>>
>> ]
>> c:\Users\qduran\Documents\development\modular-boost\boost/numeric/ublas/detail/vector_assign.hpp(33)
>> : see reference to function template instantiation 'int
>> boost::numeric::ublas::norm_inf<boost::numeric::ublas::vector_binary<E1,E2,F>>(const
>> boost::numeric::ublas::vector_expression<boost::numeric::ublas::vector_binary<E1,E2,F>>
>> &)' being compiled
>> with
>> [
>> E1=boost::numeric::ublas::matrix_column<boost::numeric::ublas::mapped_matrix<char,boost::numeric::ublas::row_major,boost::numeric::ublas::map_std<size_t,char,std::allocator<std::pair<const
>> size_t,char>>>>>
>> ,
>> E2=boost::numeric::ublas::vector<value_type,boost::numeric::ublas::unbounded_array<value_type,std::allocator<char>>>
>> , F=boost::numeric::ublas::scalar_minus<char,value_type>
>> ]
>> c:\Users\qduran\Documents\development\modular-boost\boost/numeric/ublas/detail/vector_assign.hpp(42)
>> : see reference to function template instantiation 'bool
>> boost::numeric::ublas::detail::equals<boost::numeric::ublas::matrix_column<Matrix>,C,int>(const
>> boost::numeric::ublas::vector_expression<boost::numeric::ublas::matrix_column<Matrix>>
>> &,const boost::numeric::ublas::vector_expression<C> &,S,S)' being
>> compiled
>> with
>> [
>> Matrix=boost::numeric::ublas::mapped_matrix<char,boost::numeric::ublas::row_major,boost::numeric::ublas::map_std<size_t,char,std::allocator<std::pair<const
>> size_t,char>>>>
>> ,
>> C=boost::numeric::ublas::vector<value_type,boost::numeric::ublas::unbounded_array<value_type,std::allocator<char>>>
>> , S=int
>> ]
>> c:\Users\qduran\Documents\development\modular-boost\boost/numeric/ublas/detail/vector_assign.hpp(436)
>> : see reference to function template instantiation 'bool
>> boost::numeric::ublas::detail::expression_type_check<boost::numeric::ublas::matrix_column<Matrix>,C>(const
>> boost::numeric::ublas::vector_expression<boost::numeric::ublas::matrix_column<Matrix>>
>> &,const boost::numeric::ublas::vector_expression<C> &)' being
>> compiled
>> with
>> [
>> Matrix=boost::numeric::ublas::mapped_matrix<char,boost::numeric::ublas::row_major,boost::numeric::ublas::map_std<size_t,char,std::allocator<std::pair<const
>> size_t,char>>>>
>> ,
>> C=boost::numeric::ublas::vector<value_type,boost::numeric::ublas::unbounded_array<value_type,std::allocator<char>>>
>> ]
>> *</warning text>*
>>
>> The warning is detected in the function
>> 'boost::numeric::ublas::vector_binary<E1,E2,F>::const_iterator::dereference',
>> when the binary function is called (line of code: return
>> static_cast<value_type>(functor_type::apply (t1, t2));). The
>> binary function requires two parameters of type char, however two
>> parameters of type integer are provided to he function. The
>> parameters provided to the binary function (named t1 and t2, of
>> type integer) are declared with the type
>> vector_binary::const_iterator::value_type.
>> This type is defined from vector_binary::value_type, and this
>> type is defined from F::result_type, where F is the template
>> parameter of the class vector_binary that specifies the functor
>> implementing the binary function. The functor scalar_minus
>> defines the result_type as 'typedef typename promote_traits<T1,
>> T2>::promote_type result_type;', where T1 and T2 are template
>> parameters that specifies the types of the parameters of the
>> binary function.
>>
>> The problem is located at promote_type struct, in which the
>> promoted type of two chars, two unsigned chars, two shorts or two
>> unsigned shorts is an integer and not the same type of the
>> template parameters. Following, there are the debug traces of
>> promote_traits (located at file vector_expression.hpp):
>>
>> promote_traits<char, char>::promote_type: int
>> promote_traits<unsigned char, unsigned char>::promote_type: int
>> promote_traits<short, short>::promote_type: int
>> promote_traits<unsigned short, unsigned short>::promote_type: int
>> promote_traits<int, int>::promote_type: int
>> promote_traits<unsigned int, unsigned int>::promote_type:
>> unsigned int
>> promote_traits<float, float>::promote_type: float
>> promote_traits<double, double>::promote_type: double
>>
>> I could fix the warning by adding the following template
>> specialization of promote_traits in the file traits.hpp:
>>
>> template<class X>
>> struct promote_traits<X, X> {
>> typedef typename X promote_type;
>> };
>>
>> I would like to know if the template specialization is the right
>> way to fix the problem of the promote_type struct should be revised.
>>
>> To test it, I've created a reduced version of file
>> test_matrix_vector.cpp.
>>
>> All these changes could be downloaded from the branch
>> https://github.com/jdurancomas/ublas/tree/warning_promoted_types.
>>
>> Thanks and Best Regards,
>> Joaquim Duran
>>
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>>
>>
>>
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