Re: [eigen] any remaining issues blocking beta1, speak up!

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

2010/7/4 Gael Guennebaud <gael.guennebaud@xxxxxxxxx>:
> On Sun, Jul 4, 2010 at 5:42 AM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
>> Besides the -fstrict-aliasing issue, is there anything else blocking beta1 ?

This question is still unanswered :)

I am going to prepare the release material and will be waiting for the
green light from people who reported issues in this thread and others.

Benoit


>>
>> For the -fstrict-aliasing issue, do I understand correctly that it is
>> ONLY with gcc 4.3, and not any other version?
>
> yes this is really specific to this version of GCC. I spent almost a
> day on it, and my intuition is that gcc gets confused by the deep
> hierarchy and the static cast from the top level expression to, e.g.,
> DenseBase, and back to expression via derived(). But that's only an
> intuition.
>
>>
>> If yes, do you want us to go forward and just release beta1 with a
>> "caveat", "exposes what seems to be a bug in gcc 4.3" ?
>
> yes, and the solution is to compile with -O2 -fno-strict-aliasing....
>
> gael
>
>>
>> Benoit
>>
>>
>>
>> 2010/7/3 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>:
>>> Gael: could you add your 1st example as a unit test? I understand that
>>> other tests catch the issue already, but having this simple test case
>>> can help in the future.
>>>
>>> 2010/7/3 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>:
>>>> I really can't reproduce on linux x86-64 with GCC 4.3.
>>>>
>>>> I tried compiling with -fstrict-aliasing and also with -O2
>>>> I tried both your versions, reading the program's return value like this:
>>>>
>>>> ##### 10:53:39 ~/build/eigen$ g++-4.3 z.cpp -o z -I ~/eigen -O2 && ./z
>>>> && echo "zero"
>>>> zero
>>>>
>>>> Benoit
>>>>
>>>>
>>>>
>>>> 2010/7/3 Gael Guennebaud <gael.guennebaud@xxxxxxxxx>:
>>>>> no warning.
>>>>>
>>>>>
>>>>> here is an simpler version:
>>>>>
>>>>> #include <iostream>
>>>>> #include <Eigen/Dense>
>>>>>
>>>>> int main()
>>>>> {
>>>>>  Eigen::Matrix<float,1,1> v;
>>>>>  v.setOnes();
>>>>>  return (v.cwiseAbs()-v).sum();
>>>>> }
>>>>>
>>>>> I have also simplified CwiseBinaryOp, such that the coeff(int)
>>>>> function is directly implemented in CwiseBinaryOp (not in the base
>>>>> class CwiseBinaryOpImpl) and such that it simply does:
>>>>>
>>>>> return m_rhs.coeff(0);
>>>>>
>>>>> which, in this example, should return v.coeff(0) == 1;
>>>>>
>>>>>  (so the left hand side and the functor are not used, but I remove
>>>>> them then the issue disappear).
>>>>>
>>>>> I've also changed the functor by an object of type:
>>>>>
>>>>> struct foo {
>>>>>  foo() : x(1) {}
>>>>>  int x;
>>>>> };
>>>>>
>>>>> just be sure the issue does not come from our empty functors. No success.
>>>>>
>>>>> If the left hand side (here v.cwiseAbs(), which is not used) is nested
>>>>> by reference, then the issue disappear.
>>>>>
>>>>> Also, m_rhs().data() is wrong.
>>>>>
>>>>> ...
>>>>>
>>>>> gael
>>>>>
>>>>> On Sat, Jul 3, 2010 at 3:55 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
>>>>>> Can you try compiling with
>>>>>>
>>>>>>    -Wstrict-aliasing=1
>>>>>>
>>>>>> indeed, the default value is 3, and 1 is the most aggressive warning
>>>>>> level. It could however report a lot of false positives. According to
>>>>>> `man gcc`.
>>>>>>
>>>>>> Benoit
>>>>>>
>>>>>> 2010/7/3 Gael Guennebaud <gael.guennebaud@xxxxxxxxx>:
>>>>>>> here is a simplified version:
>>>>>>>
>>>>>>> #include <iostream>
>>>>>>> #include <Eigen/Dense>
>>>>>>>
>>>>>>> template<typename A, typename B> EIGEN_DONT_INLINE int foo(const A& a,
>>>>>>> const B& b)
>>>>>>> {
>>>>>>>  return (a - b).sum() <= 0;
>>>>>>> }
>>>>>>>
>>>>>>> int main()
>>>>>>> {
>>>>>>>  Eigen::Matrix<float,1,1> v;
>>>>>>>  v.setOnes();
>>>>>>>  return foo(v.colwise().maxCoeff(),v);
>>>>>>> }
>>>>>>>
>>>>>>> which, again, fails with gcc-4.3 + strict-aliasing only....
>>>>>>> investigating to see if I can find a workaround.
>>>>>>>
>>>>>>> gael
>>>>>>>
>>>>>>> On Sat, Jul 3, 2010 at 1:03 PM, Jitse Niesen <jitse@xxxxxxxxxxxxxxxxx> wrote:
>>>>>>>> On Sat, 3 Jul 2010, Benoit Jacob wrote:
>>>>>>>>
>>>>>>>>> All is in the title. Can we release beta1 this Saturday?
>>>>>>>>
>>>>>>>> There is also the stable_norm_1 test that is failing on gcc 4.3. This seems
>>>>>>>> to be a mistake in Eigen itself.
>>>>>>>>
>>>>>>>> See the previous email I wrote:
>>>>>>>>
>>>>>>>> On Thu, 1 Jul 2010, Jitse Niesen wrote:
>>>>>>>>>
>>>>>>>>> Date: Thu, 1 Jul 2010 11:02:51 +0100 (BST)
>>>>>>>>> From: Jitse Niesen <jitse@xxxxxxxxxxxxxxxxx>
>>>>>>>>> To: Eigen mailinglist <eigen@xxxxxxxxxxxxxxxxxxx>
>>>>>>>>> Subject: Failing stable_norm_1 test
>>>>>>>>>
>>>>>>>>> Hello,
>>>>>>>>>
>>>>>>>>> I just spent some time on the stable_norm_1 test, which fails on both my
>>>>>>>>> computer and Gael's computer when using gcc 4.3. It looks similar to the
>>>>>>>>> issue
>>>>>>>>> which you solved by the empty struct magic (well done!).
>>>>>>>>>
>>>>>>>>> The details are as follows. I constructed the following (fairly) minimal
>>>>>>>>> test
>>>>>>>>> example:
>>>>>>>>>
>>>>>>>>> #include <iostream>
>>>>>>>>> #include <Eigen/Dense>
>>>>>>>>>
>>>>>>>>> int main()
>>>>>>>>> {
>>>>>>>>>  Eigen::Matrix<float,1,1> v;
>>>>>>>>>  v(0,0) = 0.1;
>>>>>>>>>  std::cerr << "blue norm = " << v.colwise().blueNorm() << "\n";
>>>>>>>>>  std::cerr << "status = " <<
>>>>>>>>> v.colwise().hypotNorm().isApprox(v.colwise().norm(), 1e-4) << "\n";
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> When compiling with g++ (version 4.3.3) -O2 -g and running under valgrind,
>>>>>>>>> this
>>>>>>>>> produces:
>>>>>>>>>
>>>>>>>>> Use of uninitialised value of size 4
>>>>>>>>>    at 0x8048F28: bool
>>>>>>>>> Eigen::DenseBase<Eigen::PartialReduxExpr<Eigen::Matrix<float, 1, 1, 0, 1,
>>>>>>>>> 1>,
>>>>>>>>> Eigen::ei_member_hypotNorm<float>, 0>
>>>>>>>>> >::isApprox<Eigen::PartialReduxExpr<Eigen::Matrix<float, 1, 1, 0, 1, 1>,
>>>>>>>>> Eigen::ei_member_norm<float>, 0>
>>>>>>>>> >(Eigen::DenseBase<Eigen::PartialReduxExpr<Eigen::Matrix<float, 1, 1, 0,
>>>>>>>>> > 1, 1>,
>>>>>>>>> Eigen::ei_member_norm<float>, 0> > const&, float) const (in
>>>>>>>>> /scratch/1/users/jitse/work/c/eigen/eigenfoo)
>>>>>>>>>    by 0x8048AF5: main (in /scratch/1/users/jitse/work/c/eigen/eigenfoo)
>>>>>>>>>
>>>>>>>>> and the same error with the same stack trace a bit later, at 0x8048F2A.
>>>>>>>>>
>>>>>>>>> The result of the program is also wrong: it should print status = 1, but
>>>>>>>>> it
>>>>>>>>> says status = 0.
>>>>>>>>>
>>>>>>>>> The error goes away when compiling with -fno-strict-aliasing.
>>>>>>>>> I tried compiling with -Wstrict-aliasing=2 but that does not produce any
>>>>>>>>> warnings.
>>>>>>>>>
>>>>>>>>> Over to the gurus!
>>>>>>>>>
>>>>>>>>> Cheers,
>>>>>>>>> Jitse
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>
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