Mac下安装Homebrew
编写并行程序要用到C的OpenMP库，Mac无法直接下载。只能通过brew下载，因此先需要安装brew。
Homebrew
一款macOS（或 Linux）缺失的软件包的管理器
安装步骤
- 官网方式安装
进入到Homebrew官网，按照提示在终端输入：
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
安装时间很久并且提示安装失败：
==> Downloading and installing Homebrew...
remote: Enumerating objects: 6, done.
remote: Counting objects: 100% (6/6), done.
remote: Compressing objects: 100% (6/6), done.
error: RPC failed; curl 18 transfer closed with outstanding read data remaining
fatal: The remote end hung up unexpectedly
fatal: early EOF
fatal: index-pack failed
Failed during: git fetch origin master:refs/remotes/origin/master --tags --force
遂放弃此方法。
估计是网络问题，采用镜像安装。
- 采用镜像地址安装
打开curl中的地址，我的是install.txt，右键以txt格式保存。
编辑原下载地址为镜像地址，即修改其中的两个链接：
BREW_REPO = “https://github.com/Homebrew/brew”.freeze
CORE_TAP_REPO = “https://github.com/Homebrew/homebrew-core”.freeze，替换成下面两句：
BREW_REPO = "https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/brew.git".freeze
CORE_TAP_REPO = "https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/homebrew-core.git".freeze
（清华大学镜像站，或者中科大的也都行）备注：实际更新时候，没有看到有CORE_TAP_REPO这一项，只有BREW_REPO（似乎是官方更新后没有了，据说没有也能执行），为防止少了有影响我还是都加上了；然后cd到txt的目录重新执行下载：
$ ruby install.txt
发现下载到一半出现Checksum mismatch错误：
==> Downloading https://homebrew.bintray.com/bottles-portable-ruby/portable-ruby-2.6.3.mavericks.bottle.tar.gz
Already downloaded: /Users/suki570/Library/Caches/Homebrew/portable-ruby-2.6.3.mavericks.bottle.tar.gz
Error: Checksum mismatch.
Expected: ab81211a2052ccaa6d050741c433b728d0641523d8742eef23a5b450811e5104
Actual: 0e38d9747803b93b4a451c38653f81f30a5c6c96e61f03ffedc2759ef9301a7e
Archive: /Users/suki570/Library/Caches/Homebrew/portable-ruby-2.6.3.mavericks.bottle.tar.gz
To retry an incomplete download, remove the file above.
Error: Failed to install vendor Ruby.
Failed during: /usr/local/bin/brew update --force
说明下载的文件和期望的hashCode对不上，删掉对应的文件就行了：
rm /Users/suki570/Library/Caches/Homebrew/portable-ruby-2.6.3.mavericks.bottle.tar.gz
最后提示下载成功：
==> Installation successful!
==> Homebrew has enabled anonymous aggregate formulae and cask analytics.
Read the analytics documentation (and how to opt-out) here:
https://docs.brew.sh/Analytics
==> Homebrew is run entirely by unpaid volunteers. Please consider donating:
https://github.com/Homebrew/brew#donations
==> Next steps:
1. Run `brew help` to get started
2. Further documentation:
https://docs.brew.sh
修改brew的镜像
直接用brew下载仍然会很慢，因此把下载路径的源也更换为清华镜像：
$ git -C "$(brew --repo)" remote set-url origin https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/brew.git
$ git -C "$(brew --repo homebrew/core)" remote set-url origin https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/homebrew-core.git
$ brew update
下载就会快不少，如果下载仍然失败可以多试几次。（可能是镜像不稳定？）
安装配置Llvm
$ brew install llvm # 安装 LLVM 编译器
$ brew install libomp # 安装 OpenMP 库
==> Downloading https://mirrors.tuna.tsinghua.edu.cn/homebrew-bottles/bottles/llvm-9.0.1.mojave.bottle.tar.gz
######################################################################## 100.0%
==> Pouring llvm-9.0.1.mojave.bottle.tar.gz
==> Caveats
To use the bundled libc++ please add the following LDFLAGS:
LDFLAGS="-L/usr/local/opt/llvm/lib -Wl,-rpath,/usr/local/opt/llvm/lib"
llvm is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.
If you need to have llvm first in your PATH run:
echo 'export PATH="/usr/local/opt/llvm/bin:$PATH"' >> ~/.bash_profile
For compilers to find llvm you may need to set:
export LDFLAGS="-L/usr/local/opt/llvm/lib"
export CPPFLAGS="-I/usr/local/opt/llvm/include"
==> Summary
/usr/local/Cellar/llvm/9.0.1: 6,833 files, 3.7GB
配置PATH：
$ echo 'export PATH="/usr/local/opt/llvm/bin:$PATH"' >> ~/.bash_profile # 将 llvm 的可执行文件添加到 PATH 目录
$ source ~/.bash_profile # 更新 .bash_profile
参考
- Mac安装home-brew
- brew 安装出现Checksum mismatch解决方法