support AppleClang with openmp

[levyfan]

support #1492
Tested with cmake 3.12.0-rc3 and Apple LLVM version 9.1.0 (clang-902.0.39.2) and libomp 5.0.1.

Howto

• install libomp by homebrew brew install libomp
• download and install cmake >= 3.12.0
• mkdir build ; cd build
• cmake ..
• make -j

[henry0312]

Oh, I didn't know AppleClang has supported OpenMP. Good news!

[levyfan]

travis-ci says:

==> Installing gcc
==> Downloading /bottles/gcc-8.1.0.sierra.bottle.1.tar.gz
curl: (3) <url> malformed
Error: Failed to download resource "gcc"
Download failed: /bottles/gcc-8.1.0.sierra.bottle.1.tar.gz
Warning: Bottle installation failed: building from source.
==> Downloading https://ftp.gnu.org/gnu/gcc/gcc-8.1.0/gcc-8.1.0.tar.xz
==> ../configure --build=x86_64-apple-darwin16.7.0 --prefix=/usr/local/Cellar/gc
==> make
No output has been received in the last 10m0s, this potentially indicates a stalled build or something wrong with the build itself.
Check the details on how to adjust your build configuration on: https://docs.travis-ci.com/user/common-build-problems/#Build-times-out-because-no-output-was-received
The build has been terminated

It seems installing gcc on macos exceed ci timeout.

[StrikerRUS]

master fails too :(

Travis problems... again!

UPD:

VSTS macOS builds are running more than one hour too. So I suppose the problem is in brew.

[henry0312]

There is something wrong with OSX on Travis.
I don't know why curl: (3) <url> malformed happens.

==> Installing gcc
==> Downloading /bottles/gcc-8.1.0.sierra.bottle.1.tar.gz
curl: (3) <url> malformed
Error: Failed to download resource "gcc"
Download failed: /bottles/gcc-8.1.0.sierra.bottle.1.tar.gz
Warning: Bottle installation failed: building from source.
==> Downloading https://ftp.gnu.org/gnu/gcc/gcc-8.1.0/gcc-8.1.0.tar.xz
==> ../configure --build=x86_64-apple-darwin16.7.0 --prefix=/usr/local/Cellar/gc
==> make

[StrikerRUS]

For issue tracking:

travis-ci/travis-ci#9865

[StrikerRUS]

Travis seems to be OK now. Rerunning builds.

[StrikerRUS]

Maybe it's better to move this to the top of the file where other cmake_minimum_required are listed?

[chivee]

@levyfan , could you also help with the updating of Documents?

[msftclas]

All CLA requirements met.

[chivee]

It will be nice if the certain version of AppleClang been specified.

[levyfan]

I am not very certain about the minimal version. I know
macOS >= el_capitan is supported by https://github.com/Homebrew/homebrew-core/blob/master/Formula/libomp.rb

[chivee]

A reasonable guess would be 9.0 (since 10.12).

[chivee]

I think we could update the Travis for macOS to using AppleClang as default. I' ll create related PR

[StrikerRUS]

@chivee

I think we could update the Travis for macOS to using AppleClang as default. I' ll create related PR

Don't it too early, because CMake 3.12 is Release Candidate now? I mean, can we install it via brew at Travis?

[levyfan]

@StrikerRUS we could use brew --HEAD for cmake now and switch to stable release later.

[levyfan]

Why is VSTS: LightGBM-Build-CI still running? 😿

[guolinke]

refer to microsoft/azure-pipelines-agent#1699 (comment)