For random matrices with integer coefficients, many of the tests here lead to
integer overflows. When taking the norm() of a row/column, the squaredNorm()
often overflows to a negative value, leading to domain errors when taking the
sqrt(). This leads to a crash on some systems. By replacing the norm() call by
a squaredNorm(), the values still overflow, but at least there is no domain
error.
Addresses https://gitlab.com/libeigen/eigen/-/issues/1856
The error generated by the compiler was:
no matching function for call to 'maxi'
RealScalar threshold = numext::maxi(tol*tol*rhsNorm2,considerAsZero);
The important part in the following notes was:
candidate template ignored: deduced conflicting
types for parameter 'T'"
('codi::Multiply11<...>' vs. 'codi::ActiveReal<...>')
EIGEN_ALWAYS_INLINE T maxi(const T& x, const T& y)
I am using CoDiPack to provide the RealScalar type.
This bug was introduced in bc000deaa Fix conjugate-gradient for very small rhs
- access violation when initializing 0x0 matrices
- exception can be thrown during stack unwind while comma-initializing a matrix if eigen_assert if configured to throw
This prevents projects that add Eigen using `add_subdirectory` from using their own custom CMAKE_BUILD_TYPE and have Eigen respect the same custom flags.
See
<https://stackoverflow.com/questions/59709148/ensuring-that-eigen-uses-avx-vectorization-for-a-certain-operation>
for an explanation of the problem this solves.
In short, for some reason, before this commit the half-packet is
selected when the array / matrix size is not a multiple of
`unpacket_traits<PacketType>::size`, where `PacketType` starts out
being the full Packet.
For example, for some data of 100 `float`s, `Packet4f` will be
selected rather than `Packet8f`, because 100 is not a multiple of 8,
the size of `Packet8f`.
This commit switches to selecting the half-packet if the size is
less than the packet size, which seems to make more sense.
As I stated in the SO post I'm not sure that I'm understanding the
issue correctly, but this fix resolves the issue in my program. Moreover,
`make check` passes, with the exception of line 614 and 616 in
`test/packetmath.cpp`, which however also fail on master on my machine:
CHECK_CWISE1_IF(PacketTraits::HasBessel, numext::bessel_i0, internal::pbessel_i0);
...
CHECK_CWISE1_IF(PacketTraits::HasBessel, numext::bessel_i1, internal::pbessel_i1);
