Re: [eigen] XLC Port: Part II - External definition of a template member function of a template class causing the problems?

[Benoit Jacob <jacob.benoit.1@xxxxxxxxx>]

2010/1/30 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>:
> 2010/1/30 Aron Ahmadia <aja2111@xxxxxxxxxxxx>:
>> Hi Benoit,
>>
>> I got that code workarounding by inlining the template function member
>> definitions into the class definition.  I decided to skip forward and
>> see if there were any other big issues that were causing the XLC
>> compiler to crash, and ei_traits appears to be another one.  The XLC
>> compiler is complaining when it tries to instansiate the ei_traits
>> template class using a single template argument (MatrixType) with the
>> error that the undefined class is not valid:
>>
>> "eigen/Eigen/src/Core/util/ForwardDeclarations.h", line 46.30:
>> 1540-1109 (S) The use of undefined class
>> "Eigen::ei_traits<Eigen::Matrix<float,3,3,0,3,3> >" is not valid.
>>
>> My suspicion is that ei_traits is not defined in a manner that XLC
>> approves of, or that it is bugging out for another reason.  I will
>> spend some time investigating this week and try to narrow down exactly
>> how and where XLC is breaking.  One possibility is that it can't
>> handle a template class instantiation to resolve another template
>> argument.  Another possibility is that it can't find a definition of
>> ei_traits that it likes.  I think I can eliminate the second
>> possibility by trying to explicitly instantiate an ei_traits object
>> with the given argument.s
>>
>> Nevermind, I just tried it.  XLC is okay with this:
>> Eigen::ei_traits<Eigen::Matrix<float,3,3,0,3,3> > a;
>>
>> and compiles, links, and runs it through a main.cpp routine.
>> It gives the same errors about ei_traits with these lines of code:
>> Eigen::Matrix<float,3,3,0,3,3> m;
>> Matrix3f m3;
>>
>> "eigen/Eigen/src/Core/util/ForwardDeclarations.h", line 44.30:
>> 1540-1109 (S) The use of undefined class
>> "Eigen::ei_traits<Eigen::Matrix<float,3,3,0,3,3> >" is not valid.
>>
>> I think this points to your use of ei_traits here:
>> template<typename MatrixType, int BlockRows=Dynamic, int BlockCols=Dynamic,
>>  int _DirectAccessStatus =
>> (ei_traits<MatrixType>::Flags&DirectAccessBit) ? HasDirectAccess :
>> NoDirectAccess> class Block;
>>
>> Some other compiler errors in the code seem to indicate that XLC is
>> unable to handle the instantiation of a template class to resolve a
>> non-class template argument.
>
> Ah, thanks, I'm starting to understand and this makes sense. I really
> hope that it is not the case:
>
>> that XLC is
>> unable to handle the instantiation of a template class to resolve a
>> non-class template argument.
>
> Because if that is the case, then it is virtually impossible to do any
> template metaprogramming with XLC :( At least I can say that we are
> doing this at many places and this is a very important device for us,
> so if that is what XLC doesn't like, fixing it would involve a very
> big set of changes and the resulting Eigen would be far clumsier
> (right now I'm not even sure that's possible).

OK, can you try this testcase to see if XLC really has a problem with
the Eigen code that you pasted. This Eigen code is accessing an
instantiation of a template class to give the default value of a
template parameter. So here is a test case for that:

#include<iostream>

template<typename T> struct has_floating_point
{
  enum { ret = 0 };
};

template<>
struct has_floating_point<float>
{
  enum { ret = 1 };
};

template<>
struct has_floating_point<double>
{
  enum { ret = 1 };
};

template<typename T, bool IsFloat = has_floating_point<T>::ret>
struct print_if_it_has_floating_point
{
  static void run()
  {
    std::cout << "Doesn't have floating point." << std::endl;
  }
};

template<typename T>
struct print_if_it_has_floating_point<T, true>
{
  static void run()
  {
    std::cout << "Has floating point." << std::endl;
  }
};

int main()
{
  print_if_it_has_floating_point<int>::run();
  print_if_it_has_floating_point<float>::run();
  print_if_it_has_floating_point<double>::run();
}


Benoit



>
> Benoit
>
>
>>
>> Cheers,
>> Aron
>>
>> On Sat, Jan 30, 2010 at 4:56 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
>>> 2010/1/27 Aron Ahmadia <aja2111@xxxxxxxxxxxx>:
>>>> Hi all,
>>>>
>>>> I'm still looking at the port, and I've managed to narrow down the
>>>> problem.  For those of you who've been following along at home, XLC
>>>> has been throwing this error when trying to compile the Eigen files:
>>>>                                              [0]
>>>> "eigen/Eigen/src/Core/SelfAdjointView.h", line 147.81: 1540-0716 (S)
>>>> The template argument "Eigen::SelfAdjointView" does not match the
>>>> template parameter "class T".
>>>> "eigen/Eigen/src/Core/SelfAdjointView.h", line 134.112: 1540-0716 (S)
>>>> The template argument "Eigen::SelfAdjointView" does not match the
>>>> template parameter "class T".
>>>>
>>>> Suspiciously, there's no trace of SelfAdjointView being used as a
>>>> template parameter argument anywhere in there, or any trace of a
>>>> parameter named 'class T'.
>>>>
>>>> So I decided to create a new test file, slowly adding in the Eigen
>>>> header files from Core until I got compiler errors.  Here's the
>>>> current file: http://pastebin.com/m267235e7
>>>>
>>>> If you'll notice, SelfAdjointView.h is being successfully included
>>>> here.  What causes the breakage is SelfadjointProduct.h.  This
>>>> actually isn't that surprising, since a function that declared in
>>>> SelfAdjointView.h is later defined in SelfadjointProduct.h (By the
>>>> way, should this be renamed to SelfAdjointProduct.h to fit the rest of
>>>> the naming scheme better?)
>>>>
>>>> Here is the declaration and the definition:
>>>>
>>>> template<typename DerivedU>
>>>> SelfAdjointView& rankUpdate(const MatrixBase<DerivedU>& u, Scalar alpha)
>>>>
>>>>
>>>> template<typename MatrixType, unsigned int UpLo>
>>>> template<typename DerivedU>
>>>> SelfAdjointView<MatrixType,UpLo>& SelfAdjointView<MatrixType,UpLo>
>>>> ::rankUpdate(const MatrixBase<DerivedU>& u, Scalar alpha)
>>>> {
>>>>  typedef ei_blas_traits<DerivedU> UBlasTraits;
>>>>  typedef typename UBlasTraits::DirectLinearAccessType ActualUType;
>>>>  typedef typename ei_cleantype<ActualUType>::type _ActualUType;
>>>>  const ActualUType actualU = UBlasTraits::extract(u.derived());
>>>>
>>>>  Scalar actualAlpha = alpha * UBlasTraits::extractScalarFactor(u.derived());
>>>>
>>>>  enum { IsRowMajor = (ei_traits<MatrixType>::Flags&RowMajorBit) ? 1 : 0 };
>>>>
>>>>  ei_selfadjoint_product<Scalar,
>>>>    _ActualUType::Flags&RowMajorBit ? RowMajor : ColMajor,
>>>>    ei_traits<MatrixType>::Flags&RowMajorBit ? RowMajor : ColMajor,
>>>>    !UBlasTraits::NeedToConjugate, UpLo>
>>>>    ::run(_expression().cols(), actualU.cols(), &actualU.coeff(0,0),
>>>> actualU.stride(),
>>>>          const_cast<Scalar*>(_expression().data()),
>>>> _expression().stride(), actualAlpha);
>>>>
>>>>  return *this;
>>>> }
>>>>
>>>> So according to this page here:
>>>> http://www.comeaucomputing.com/techtalk/templates
>>>>
>>>> You're not allowed to do the above because SelfAdjointView is the
>>>> 'primary template argument'.  Unfortunately, the code refuses to
>>>> compile if the template arguments are removed.
>>>
>>> I'm sorry, I still don't understand what is not allowed with the code
>>> that you pasted here?
>>>
>>> Benoit
>>>
>>>
>>>
>>
>>
>>
>