Using CustomVector with const arrays

[Mikhail Katliar]

It seems currently impossible to use a cost-pointer to raw array with CustomVector:

#include <blaze/Math.h>

int main(int argc, char ** argv)
{
    using namespace blaze;

    double const raw_data[3] = {1., 2., 3.};

    CustomVector<double, unaligned, unpadded> c1(raw_data, 3);    // <-- Compiler error!
    CustomVector<double const, unaligned, unpadded> c2(raw_data, 3);    // <-- Compiler error!

    return 0;
}

Compiler output:

blaze_const_custom_vector.cpp:10:47: error: no matching constructor for initialization of 'CustomVector<double, unaligned, unpadded>'
    CustomVector<double, unaligned, unpadded> c1(raw_data, 3);
                                              ^  ~~~~~~~~~~~
/usr/local/include/blaze/math/dense/CustomVector.h:481:20: note: candidate constructor not viable: no known conversion from 'const double [3]' to
      'double *' for 1st argument
   explicit inline CustomVector( Type* ptr, size_t n );
                   ^
/usr/local/include/blaze/math/dense/CustomVector.h:485:20: note: candidate constructor template not viable: requires 3 arguments, but 2 were provided
   explicit inline CustomVector( Type* ptr, size_t n, Deleter d );
                   ^
/usr/local/include/blaze/math/dense/CustomVector.h:488:20: note: candidate constructor template not viable: requires 4 arguments, but 2 were provided
   explicit inline CustomVector( Type* ptr, size_t n, size_t nn, Deleter d );
                   ^
/usr/local/include/blaze/math/dense/CustomVector.h:490:11: note: candidate constructor not viable: requires single argument 'v', but 2 arguments were
      provided
   inline CustomVector( const CustomVector& v );
          ^
/usr/local/include/blaze/math/dense/CustomVector.h:491:11: note: candidate constructor not viable: requires single argument 'v', but 2 arguments were
      provided
   inline CustomVector( CustomVector&& v ) noexcept;
          ^
/usr/local/include/blaze/math/dense/CustomVector.h:482:20: note: candidate constructor not viable: requires 3 arguments, but 2 were provided
   explicit inline CustomVector( Type* ptr, size_t n, size_t nn );
                   ^
/usr/local/include/blaze/math/dense/CustomVector.h:480:20: note: candidate constructor not viable: requires 0 arguments, but 2 were provided
   explicit inline CustomVector();
                   ^
/usr/local/include/blaze/math/dense/CustomVector.h:717:4: error: static_assert failed "Const-qualified type detected"
   BLAZE_CONSTRAINT_MUST_NOT_BE_CONST         ( Type );
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/local/include/blaze/util/constraints/Const.h:80:4: note: expanded from macro 'BLAZE_CONSTRAINT_MUST_NOT_BE_CONST'
   static_assert( !::blaze::IsConst<T>::value, "Const-qualified type detected" )
   ^              ~~~~~~~~~~~~~~~~~~~~~~~~~~~
blaze_const_custom_vector.cpp:11:53: note: in instantiation of template class 'blaze::CustomVector<const double, false, false, false>' requested here
    CustomVector<double const, unaligned, unpadded> c2(raw_data, 3);
                                                    ^

One could use const_cast<> to strip the const-qualifier from the pointer, which is not the right thing I suppose.

What is the motivation for disallowing const-types in CustomVector? Should the support for const-arrays be added in CustomVector or implemented in a different class e.g. ConstCustomVector?

[Klaus Iglberger]

Hi Mikhail!

Thanks for pointing out this issue with CustomVector. It appears to be an oversight that it is currently not possible to create a CustomVector with a pointer to a constant array. We expect that this problem can be solved quickly and we will provide a solution shortly. Again, thanks a lot,

Best regards,

Klaus!

[Klaus Iglberger]

Summary

The feature has been implemented and tested as required. It is immediately available via cloning the Blaze repository and will be officially released in Blaze 3.2.

CustomVector

It is now possible to create a CustomVector instance by passing a pointer to a const array:

using namespace blaze;

double const raw_data[3] = {1., 2., 3.};

CustomVector<double const, unaligned, unpadded> a(raw_data, 3);

Please note that it is necessary to explicitly const-qualify the type of elements!

CustomMatrix

It is now also possible to create a CustomMatrix instance by passing a pointer to a const array:

using namespace blaze;

double const raw_data[3] = {1., 2., 3., 4., 5., 6., 7., 8., 9.};

CustomMatrix<double const, unaligned, unpadded> A( raw_data, 3, 3 );

Please note that also in this case it is necessary to explicitly const-qualify the type of elements!

[Mikhail Katliar]

Great, thanks for fixing it so quickly, Klaus!

[Klaus Iglberger]

My pleasure. Thanks for pointing out this defect!