在 Mac OS 上使用 OpenMP 和 C++11答案

【问题标题】：Using OpenMP with C++11 on Mac OS在 Mac OS 上使用 OpenMP 和 C++11
【发布时间】：2017-02-20 03:32:51
【问题描述】：

我正在尝试在我的 C++11 代码中使用一些 OpenMP 多线程功能，例如：

#pragma omp parallel for

当我尝试编译时：

clang++ -std=c++11 -stdlib=libc++ -fopenmp main.cpp -o main.o

我收到以下错误：

clang: error: unsupported option '-fopenmp'

我也尝试使用以下方法进行编译：

g++ -fopenmp main.cpp -o main.o

但这给出了完全相同的错误。

如果您能告诉我如何在 Mac OS 10.12 上编译具有 OpenMP 功能的 C++11 代码，将不胜感激。此处和其他地方的帖子上的其他问题解释了为 OpenMP 编译 C 代码，但是，我找不到 C++11 的任何内容。

我在尝试安装 libiomp 时收到错误消息：

$ brew install libiomp
==> Auto-updated Homebrew!
Updated 1 tap (homebrew/core).
==> Updated Formulae
ansible-cmdb        djview4             khard               oysttyer            shyaml              yazpp             
asciinema2gif       doctl               macvim              pazpar2             vala                you-get           
avro-c              elixir              mailhog             python              vdirsyncer          youtube-dl        
bash-git-prompt     file-roller         meson               python3             vim               
commandbox          glib                metaproxy           rtv                 x265              
consul-backinator   gtkextra            offlineimap         s-search            xonsh             

Error: Could not link:
/usr/local/share/doc/homebrew

Please delete these paths and run `brew update`.
Error: Could not link:
/usr/local/share/man/man1/brew.1

Please delete these paths and run `brew update`.
Error: No available formula with the name "libiomp" 
==> Searching for similarly named formulae...
Error: No similarly named formulae found.
==> Searching taps...
Error: No formulae found in taps.

如果我使用 g++-6 运行，基于 Mark Setchell 在下面的帖子，它可以正常工作，谢谢，但是我收到以下警告，希望有任何关于如何避免这些问题的建议：

$ /usr/local/bin/g++-6 -std=c++11 -fopenmp main.cpp -o main.o
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:4:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:4:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:89:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:89:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:551:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:551:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:1432:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:1432:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:1799:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:1799:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:1995:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:1995:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2033:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2033:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2425:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2425:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2559:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2559:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2597:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2597:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2672:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2672:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2837:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2837:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2962:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:2962:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:3139:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:3139:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:3442:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:3442:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:3588:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:3588:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:3630:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:3630:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:5253:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:5253:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:5452:11: warning: section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/jr/30r6h4cj4tl48q_cg9bt5f5h0000gn/T//ccq73Zfg.s:5452:11: note: change section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~

【问题讨论】：

标签： c++ c++11 openmp macos-sierra

【解决方案1】：

更新答案

自从我在下面给出原始答案以来，情况已经有所改善，您可以轻松地将 OpenMP 与 clang++ 编译器一起使用 - 好啊！

为此，首先使用 homebrew 安装brew install libomp：

brew install libomp

然后在使用clang++ 时，使用这些标志：

clang++ -Xpreprocessor -fopenmp main.cpp -o main -lomp

原答案

如果你想在 OSX 上编译 C++11 OpenMP 代码，最简单的方法是使用 gcc，你可以通过 homebrew 安装它。

首先，检查可用的选项：

brew options gcc

样本输出

--with-all-languages
    Enable all compilers and languages, except Ada
--with-java
    Build the gcj compiler
--with-jit
    Build the jit compiler
--with-nls
    Build with native language support (localization)
--without-fortran
    Build without the gfortran compiler
--without-multilib
    Build without multilib support
--HEAD
    Install HEAD version

所以，我怀疑你想要：

brew install gcc --without-multilib --without-fortran

安装后，您需要确保您使用的是 homebrew 版本，而不是 Apple 提供的版本。您需要知道homebrew 将所有内容安装在/usr/local/bin 中，并且C++ 编译器是g++-6。所以，你要么需要编译：

/usr/local/bin/g++-6 -std=c++11 -fopenmp main.cpp -o main

或者，在您的登录配置文件中设置您的 PATH：

export PATH=/usr/local/bin:$PATH

那么你可以这样做：

g++-6 -std=c++11 -fopenmp ...

请注意，如果您选择上面的第二个选项（即export PATH=... 选项），您将需要在当前会话中同时键入export 命令以激活它，或者注销并重新登录您的配置文件命令仅在登录时执行。

AFAIK，无需显式安装 libiomp - 不知道您为什么这样做。

【讨论】：

马克，谢谢！效果很好。我确实收到了一些警告，我在上面发布了，请您也提供一些建议。
我想这与您以前从未见过的不成功尝试有关。我会尝试brew rm libiomp --force 并重建您的代码并重试。如果失败，我会尝试brew rm gcc --force，然后按照我上面的回答再次安装gcc。
谢谢，马克，会的。
brew options gcc 给出的当前选项不包括--without-multilib 或--without-fortran
@OmarHaque 感谢您指出这一点 - 我已经更新了我的答案。

【解决方案2】：

XCode 附带的 Clang 不支持 OpenMP，但是来自 llvm.org 的 Clang 支持。有instructions for how to install it。

默认情况下，在 OSX 上，GCC 只是 Clang 的符号链接（根据 Compile OpenMP programs with gcc compiler on OS X Yosemite 的评论）。你可以从 Homebrew 安装真正支持 OpenMP 的 GCC。

【讨论】：

感谢您的回复，我在尝试安装 libiomp 时遇到错误更新了我的原始帖子。
您不再需要显式安装 libiomp。实际上，您将其称为 libiomp 的事实表明您使用的是旧版本，因为在最新的 LLVM 版本（默认启用 OpenMP）中，该库是 libomp。