Google Tensorflow 源码编译（二）：Bazel<v0.1.0>

这几天终于把tensorflow安装上了，中间遇到过不少的问题，这里记录下来。供大家想源码安装的参考。

安装环境：POWER8处理器，Docker容器Ubuntu14.04镜像。

Build Bazel<v0.1.0> for IBM POWER8 CPU from Source Code

My computer's os is ubuntu 14.04 , and I want to install bazel, There is only java7 available, so I choose bazel 0.1.0.
Here are the steps that I succeed to install bazel 0.1.0 on my computer:

1. Get source code
　　git clone https://github.com/bazelbuild/bazel.git
　　git checkout 0.1.0

2. Install protobuf
　　Check which version is needed:

　　opuser@nova:~/tensorflow/bazel-0.1.0$ ls third_party/protobuf/
　　LICENSE protobuf-java-3.0.0-alpha-3.jar protoc-linux-x86_64.exe protoc-osx-x86_32.exe protoc-windows-x86_32.exe
　　README.md protoc-linux-x86_32.exe protoc-linux-x86_64.real protoc-osx-x86_64.exe protoc-windows-x86_64.exe

　　protobuf-java-3.0.0-alpha-3.jar is the jar file bazel uses. so we need to install protobuf with version <3.0.0-alpha-3> , you can refer to "Build Protobuf<v3.0.0-alpha-3> for IBM POWER8 CPU from Source Code" to build protobuf .

3. Create a link protoc-linux-x86_64.exe to protoc binary file
　　such as : ln -s /usr/bin/protoc $(pwd)/ third_party/protobuf/protoc-linux-x86_64.exe

4. Install other dependencies
4.1 sudo apt-get install zlib1g-dev zip unzip openjdk-7-jre openjdk-7-jdk
4.2 add java path to ~/.bashrc
　　export JAVA_HOME=/usr/lib/jvm/java-7-openjdk-ppc64el
　　export JRE_HOME=${JAVA_HOME}/jre
　　export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
　　export PATH=${JAVA_HOME}/bin:$PATH

5. Modify bazel source code to support POWER cpu
5.1 in src/main/java/com/google/devtools/build/lib/util/CPU.java
　　in enum "public enum CPU" add
　　POWER("power", ImmutableSet.of("power", "power64le", "power64be", "ppc")),

5.2 in /src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java
　　in function "public static class HostCpuConverter implements Converter<String>"add:
　　case POWER:
　　return "power";
5.3 in tools/cpp/CROSSTOOL, add
　　default_toolchain {
　　cpu: "power"
　　toolchain_identifier: "local_linux"
　　}
5.4 in third_party/BUILD, add
　　config_setting(
　　name = "power",
　　values = {"host_cpu": "power"},
　　)
5.5 in scripts/bootstrap/buildenv.sh, add
　　MACHINE_IS_64BIT='yes'

6. Compile bazel
　　./compile // better to see step 7 before run ./compile
　　after a long time, a message displayed:
　　Build successful! Binary is here: /home/opuser/tensorflow/tools/bazel-0.1.0/output/bazel

7. Problems during compiling
　　It is not easy to build bazel from source code. not to mention that I build it in a docker container. there are mainly two problems.

7.1 namespace-sandbox
　　<error: mount() permission denied!>
　　bazel may choose to build a sanbox which uses namespace . but there are priority strictions in container. to avoid this problem, you can choose not to build sandbox .
　　I refer to dcreager's solution posted at https://github.com/bazelbuild/bazel/issues/418. create a bazelrc and use command "BAZELRC=/tmp/bazelrc ./compile.sh" to compile the code. the bazelrc file  contains:  
　　startup --batch
　　build --spawn_strategy=standalone --genrule_strategy=standalone

7.2 openjdk-7

　　<error: unrecognized option -client!>

　　The java installed on my computer does not support -client option, but -server option is ok. just as the issue  opened at

　　https://github.com/bazelbuild/bazel/issues/56

　  Although there is a commit about this:

　　https://github.com/bazelbuild/bazel/commit/1fa163c42ee26a72c21c118ec820d677a431ee49#commitcomment-13207150.

　　But it does not work to me. so I changed all the -client option to -server.

8. Reference

Can't run Bazel as part of a Docker build due to sandboxing issues
https://github.com/bazelbuild/bazel/issues/418
Compiling the Java example with SAP JVM does not work
https://github.com/bazelbuild/bazel/issues/56
Add jvm_opts attribute to the java_toolchain rule
https://github.com/bazelbuild/bazel/commit/1fa163c42ee26a72c21c118ec820d677a431ee49#commitcomment-13207150.