With Cray compiler wrappers (implicitly tested on OLCF Spock) the
BLAS and LAPACK libraries are automatically linked as necessary through
the wrapper script and programming environment. With this change, the
configure output is:
```
-- Found BLAS: implicitly linked
<snip>
-- Found LAPACK: implicitly linked
```
rather than
```
-- Found BLAS: 1
<snip>
-- Found LAPACK: LAPACK_LIBRARIES-PLACEHOLDER-FOR-EMPTY-LIBRARIES
```
Logic added by commit 4c74c86f40 (FindBLAS/LAPACK: Add support for the
Fujitsu SSL2 library, 2021-01-27, v3.21.0-rc1~402^2~1) accidentally
expressed a boolean condition without proper grouping. The pattern was
then copied by commit 2c9e623e31 (Find{BLAS,LAPACK}: Add support for the
NVHPC LAPACK library, 2021-05-05, v3.21.0-rc1~192^2). The resulting
logic incorrectly tries Fujitsu and NVHPC vendors even after results are
found from another vendor, and then erases those. Fix the grouping.
Fixes: #22403
Since commit 20ab504591 (FindBLAS: Do not statically link against iomp5
in the case of Intel MKL, 2021-04-11), we no longer find MKL's BLAS when
using the GNU compiler because FindOpenMP chooses libgomp instead of
libiomp5, and mkl_intel_thread depends on the latter. Revert the change
for now. A new approach will be needed to solve the original problem.
Issue: #21811
Now that `CHECK_{BLAS,LAPACK}_LIBRARIES` are functions, we can set
`CMAKE_FIND_LIBRARY_SUFFIXES` locally without affecting the global
state. This avoids the need for local state switching that was added in
commit 9ef82d95d8 (FindBLAS: Fix detection of OpenMP as dependency of
BLA_STATIC, 2021-04-07, v3.20.1~3^2), so remove that.
Refactoring in commit 4c74c86f40 (FindBLAS/LAPACK: Add support for the
Fujitsu SSL2 library, 2021-01-27) was done in order to support calling
`find_library` on the dependencies as well as the candidate libraries.
However, it broke a few things:
* Intel MKL's BLAS/LAPACK are no longer found. We specify their
dependencies using `-l...` flags, so we should not try to use
`find_library` for them.
* The dependencies are repeated because we accumulate them in the
`find_library` search loop and then append them at the end too.
Revert the incorrect part of the refactoring. Retain the flags part
needed for the Fujitsu vendor.
Fixes: #22056
Update the change from commit f7f3d8987a (FindBLAS: Add dependency of
OpenBLAS on OpenMP for BLA_STATIC, 2020-11-10, v3.20.0-rc1~492^2):
* If C is not enabled, find CXX OpenMP libraries instead.
* Do not use BLA_STATIC's custom CMAKE_FIND_LIBRARY_SUFFIXES for OpenMP.
It can break projects that already call `find_package(OpenMP)` and
expect a shared library. Whether OpenMP is static is orthogonal to
whether BLAS is static.
Fixes: #22039
Issue: #16221
This also does some additional work to fix issues with
libraries provided only via compiler options and no explicit
library names.
Co-Author: Yuichiro Utsumi <utsumi.yuichiro@jp.fujitsu.com>
The patch also updates the documentation to explicitly state
that Intel10_32 stands for threaded case (linked with Intel OpenMP).
Later, one may need to add Intel10_32_seq to support linking
with the sequential version of Intel MKL.
Fixes: #20857
Even though Intel MKL typically puts the libraries under
`$MKLROOT/lib/$arch_$os` some installations may still use
`$MKLROOT/lib/$arch/` path. Ideally, `$arch` should be a
symlink to `$arch_$os`, but sometimes the opposite happens
(for instance, see Intel MKL distribution in Arch Linux [1]),
and sometimes only `$arch` directory alone is present.
This patch extends the search list with `$MKLROOT/lib/$arch` with
lower priority than `$MKLROOT/lib/$arch_$os`, as the latter is the
official path to Intel MKL libraries.
It is also worth mentioning that Intel MKL Link Line Adviser [2]
recommends using `$MKLROOT/lib/$arch` directory in a link line:
```
-L${MKLROOT}/lib/intel64 -Wl,--no-as-needed -lmkl_intel_lp64
-lmkl_sequential -lmkl_core -lpthread -lm -ldl
```
[1] https://www.archlinux.org/packages/community/x86_64/intel-mkl/files/
[2] https://software.intel.com/content/www/us/en/develop/articles/intel-mkl-link-line-advisor.html
This is required if MKLROOT points to the subdirectory .../mkl/ instead of
the root of an Intel MKL library installation. Only in this case the MKL
will be searched starting from the parent directory, to detect relevant
dependencies in parallel subdirectories, like 'compiler' and 'tbb'.
Previously the search in the dynamic linker paths 'LIB', 'LD_LIBRARY_PATH'
and 'DYLD_LIBRARY_PATH' was dependent on the value of the environment
variable 'MKLROOT'. If MKLROOT was given, the dynamic linker paths where
not searched. This seems slightly counter-intuitive.
This PR changes the behavior so that MKLROOT is searched first, but if
unsuccesful, the dynamic linker paths are tried as well.
