Rewrite FindMETIS to provide imported targets

Summary

This MR adds imported-targets to the FindMETIS.cmake module, following modern cmake guidelines.

Details

Instead of exporting include directories and libraries as variables, the find modules exports an imported target that contains all the necessary information to include and link METIS. The find module introduces the imported target: METIS::METIS.

Scotch-METIS

If you want to use scotch-metis is (partially) compatible library replacement, you have to set the option ENABLE_SCOTCH_METIS to true. It is an explicit option, since the scotch-metis library is not really compatible to metis. It provides only a small subset of the functions, with slightly different parameters and in some versions a missing return value. So, you have to program scotch-metis differently from METIS. If enabled, the Scotch library is search for by FindPTScotch and METIS is linked against PTScotch::Scotch if found. In this case the preprocessor constant HAVE_SCOTCH_METIS is set.

Depending the version of Scotch, a different METIS API version is provided. Scotch < 6.0.7 provides only METIS API 3, but with Scotch 6.0.9 both APIs (3 or 5) are possible. Whether Scotch ships a compiled METIS API 5 or 3 depends on how scotchmetis was compiled. For recent Scotch libraries you have to provide the additional cmake variable SCOTCH_METIS_VERSION=(3|5) to tell cmake how Scotch is compiled. The API version of METIS is provided as preprocessor constant METIS_API_VERSION and typically corresponds to the METIS major version.

Depends on !820 (merged) for linking against PTScotch::Scotch

ToDo

• Check for the failing Pipelines
• Design a proper test for the functionality of METIS
• Test Scotch backend for METIS

changed milestone to %New CMake Build-System

added buildsystem label

changed the description

mentioned in merge request !822 (merged)

changed the description

Again, is there a warning, that we only support Metis 5 or newer?

This must be tested not inside the find module, but when you call find_package:

find_package(METIS 5.0)

You are right. I am so used to the Dune way (brain washed?), that I forgot about the CMake way.

added 2 commits

• f122ab49 - Detection of Scotch requirement corrected
• 0ca884d2 - Test for METIS and the FindMETIS package added

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marked as a Work In Progress

changed the description

changed the description

Dune requires version METIS >= 5.0, right? At least, this is stated in the old cmake find module. Scotch implements the interface for METIS 4, even in the Scotch 6.0. So, do we really want to support Scotch-METIS here? If yes, we should add an interface layer to call the different METIS versions, like we have done for the idx_t and real_t types in repartition.hh in dune-istl. Since METIS is provided by dune-common, this layer should be in dune-common as well.

added 3 commits

• 28eebcb5 - Remove unnecessary two-stage find procesures
• f41d3fc9 - Move HAVE_METIS and dune_register_package_flags to AddMETISFlags
• 58f16ca8 - Allow for using scotchmetis by providing typedefs

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resolved all threads

mentioned in issue dune-istl#94

added 35 commits

• 58f16ca8...0febb2ae - 28 commits from branch master
• 41d646df - Rewrite FindMETIS to provide imported targets
• 4934bb32 - Detection of Scotch requirement corrected
• fe1bc923 - Test for METIS and the FindMETIS package added
• 22fe282c - Remove unnecessary two-stage find procesures
• 63744eea - Move HAVE_METIS and dune_register_package_flags to AddMETISFlags
• 314335cc - Allow for using scotchmetis by providing typedefs
• 41eaf689 - update test for scotch-metis in FindMETIS

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In summary:

• scotchmetis does not provide a full METIS implementation, but just wrappers around some functions.
• scotchparmetis does not need scotchmetis, but just scotch
• source, debian, open-suse, fedora packages, all provide the scotchmetis library in a different form
• we have scotchmetis as package in the docker CI images

Proposal:

• Provide scotchmetis only on request, e.g. by introducing an option, or a package component
• By default, metis needs to specify its version. If scotch is requested, set version to API compatibility version: version 3 for scotch < 6.07, else version 5 if METIS version 5 is requested, otherwise version 3 as well
• Provide METIS API version in config.h file: e.g. METIS_API_VERSION = METIS_VER_MAJOR
• Provide flag whether scotchmetis is enable in config.h file: e.g. HAVE_SCOTCH_METIS=1
• follow a similar strategy for parmetis.

added 1 commit

• 29fff6e2 - rewritten find scotch-metis and metistest

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marked the checklist item Design a proper test for the functionality of METIS as completed

marked the checklist item Test Scotch backend for METIS as completed

changed the description

added 1 commit

• 23051120 - search for Scotch component only

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marked the checklist item Check for the failing Pipelines as completed

unmarked as a Work In Progress

resolved all threads

I'd try to reduce the number of combinations. Otherwise it will be difficult to test. I propose the limit the support of PT Scotch to 6.0.7 or newer. The problem is Debian (buster has 6.0.6, bullseye will provide 6.0.9). Ubuntu comes with 6.0.7 or newer since 19.10.

@markus.blatt Do you have any version restrictions regarding Scotch? Or do you know some of the projects you are involved?

resolved all threads

Thanks. Seems to work on Debian stable. Can we add some more documentation on the SCOTCH_METIS_VERSION? I do not understand what to put there.

mentioned in issue infrastructure/issues0#64 (closed)

mentioned in merge request !856 (merged)

added 1 commit

• c5679e82 - extended the documentation of the SCOTCH_METIS_VERSION variable

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added 56 commits

• c5679e82...17685a51 - 46 commits from branch master
• 6844cbc2 - Rewrite FindMETIS to provide imported targets
• f742dfbf - Detection of Scotch requirement corrected
• d60ee118 - Test for METIS and the FindMETIS package added
• 361ad03a - Remove unnecessary two-stage find procesures
• 5493549b - Move HAVE_METIS and dune_register_package_flags to AddMETISFlags
• fb787206 - Allow for using scotchmetis by providing typedefs
• a3981673 - update test for scotch-metis in FindMETIS
• 937aad3a - rewritten find scotch-metis and metistest
• 8a28ec9b - search for Scotch component only
• c497fe46 - extended the documentation of the SCOTCH_METIS_VERSION variable

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added 1 commit

• fee55cf6 - Rewrite FindMETIS module.

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resolved all threads

This find-module is now cleaned up. Some documentation is added for the scotch-metis compatibility library and the corresponding cmake flags. A test is added to dune-common and the commits to this MR are squashed.

Any objections to merging this?

I am all in favor of merging this. Thanks for putting so much effort into this MR! Once you are ready, I'll merge.

added 1 commit

• ef084a74 - final cleanup of FindMETIS

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added 1 commit

• 3fc9ad0b - Correct some typos in metistest

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resolved all threads

Can be merged now.

added 5 commits

• 3fc9ad0b...4dced988 - 4 commits from branch master
• 335d9f24 - Rewrite FindMETIS module

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I took the liberty to squash the commits and alter the commit message.

enabled an automatic merge when the pipeline for 335d9f24 succeeds

mentioned in commit acb90738

merged

mentioned in issue #222 (closed)

I highly appreciate modernizing the cmake scripts, but doing it in a way that Dune is not working with Debian stable and/or Ubuntu LTS basically renders it unusable in production for me