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

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

So, it looks like we're ready to release beta1. The -fstrict-aliasing
issue with gcc 4.3 is something we'll mention as a caveat.

I have to go to work now but can release it tonight. Alternatively, if
Gael or someone else wants to do it, you're very welcome.

Benoit

2010/7/4 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@xxxxxxxxxxxxxxxxxx> 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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