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Ublas : |
Subject: Re: [ublas] Fix conversion from integer to char
From: Nasos Iliopoulos (nasos_i_at_[hidden])
Date: 2016-01-04 10:09:02
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<const
> size_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<const
> size_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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