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

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

Besides the -fstrict-aliasing issue, is there anything else blocking beta1 ?

For the -fstrict-aliasing issue, do I understand correctly that it is
ONLY with gcc 4.3, and not any other version?

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" ?

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
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>
>