Compiling Tensorflow from sources

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Compiling Tensorflow from sources

First of all, we need a clean Ubuntu VM. I installed an Ubuntu 18.04LTS x86_64 with 80GB HD, 4 CPUs and 4GB of RAM.

After installing and setting the network, update: 

apt-get update
apt-get upgrade

Then install basic tools: 

apt-get install python3-numpy python3-dev python3-pip python3-wheel
apt-get install python

Then, download and install Bazel: 

wget https://github.com/bazelbuild/bazel/releases/download/0.15.2/bazel_0.15.2-linux-x86_64.deb
apt-get install ./bazel-0.15.2-linux-x86_64.deb

Then, download and extract Tensorflow source code: 

wget https://github.com/tensorflow/tensorflow/archive/v1.9.0.tar.gz
tar xvfz v1.9.0.tar.gz
cd tensorflow-1.9.0

and configure it: 

./configure

During the configuration, specify the python location (in this case, /usr/bin/python3) and just accept the defaults.

After that, it's time to compile: 

bazel build --config=opt //tensorflow/tools/pip_package:build_pip_package

during the compilation process, it may show many warnings.

The entire process will take about 2-3 hours.

To create a pip package: 

./bazel-bin/tensorflow/tools/pip_package/build_pip_package /tmp/tensorflow_pkg

Under /tmp/tensorflow_pkg there will be the pip package: tensorflow-1.0-cp36-linux_x86_64.whl

It can be moved to the target machine and installed: 

pip install /tmp/tensorflow_pkg/tensorflow-1.0-cp36-linux_x86_64.whl

Cross Compiling for Nanopi Neo (arm)

First of all, let's give the machine at least 8GB of RAM (otherwise you will run into a subtle 'Error 4' when compiling).

Download the toolchain from linaro: 

https://releases.linaro.org/components/toolchain/binaries/latest/arm-linux-gnueabihf/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf.tar.xz
tar xvf gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf.tar.xz

In tensorflow directory:

File BUILD: 

package(default_visibility = ["//visibility:public"])

cc_toolchain_suite(
    name = "toolchain",
    toolchains = {
        "armv7l|compiler": ":cc-compiler-armv7l",
    },
)

 filegroup(
     name = "empty",
     srcs = [],
)

filegroup(
    name = "arm_linux_all_files",
    srcs = [
        "@toolchain_target_armv7l//:compiler_pieces",
    ],
)

cc_toolchain(
    name = "cc-compiler-armv7l",
    all_files = ":arm_linux_all_files",
    compiler_files = ":arm_linux_all_files",
    cpu = "armv7l",
    dwp_files = ":empty",
    dynamic_runtime_libs = [":empty"],
    linker_files = ":arm_linux_all_files",
    objcopy_files = "arm_linux_all_files",
    static_runtime_libs = [":empty"],
    strip_files = "arm_linux_all_files",
    supports_param_files = 1,
)

Add to the end of the file WORKSPACE: 

new_local_repository(
   name = 'toolchain_target_armv7l',
   path = '/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf',
   build_file = 'arm_compiler.BUILD'
)

File CROSSTOOL: 

major_version: "local"
minor_version: ""
default_target_cpu: "armv7l"

default_toolchain {
  cpu: "armv7l"
  toolchain_identifier: "armv7l"
}

toolchain {
  abi_version: "armv7l"
  abi_libc_version: "armv7l"
  builtin_sysroot: ""
  compiler: "compiler"
  host_system_name: "armv7l"
  needsPic: true
  supports_gold_linker: false
  supports_incremental_linker: false
  supports_fission: false
  supports_interface_shared_objects: false
  supports_normalizing_ar: true
  supports_start_end_lib: false
  supports_thin_archives: true
  target_libc: "armv7l"
  target_cpu: "armv7l"
  target_system_name: "armv7l"
  toolchain_identifier: "armv7l"

  tool_path { name: "ar" path: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-ar" }
  tool_path { name: "compat-ld" path: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-ld" }
  tool_path { name: "cpp" path: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-cpp" }
  tool_path { name: "gcc" path: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-gcc" }
  tool_path { name: "gcov" path: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-gcov" }
  tool_path { name: "ld" path: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-ld" }
  tool_path { name: "nm" path: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-nm" }
  tool_path { name: "objcopy" path: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-objcopy" }
  objcopy_embed_flag: "-I"
  objcopy_embed_flag: "binary"
  tool_path { name: "objdump" path: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-objdump" }
  tool_path { name: "strip" path: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-strip" }

  cxx_builtin_include_directory: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/include"
  cxx_builtin_include_directory: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/lib/gcc/arm-linux-gnueabihf/7.3.1/include"
  cxx_builtin_include_directory: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/arm-linux-gnueabihf/include"
  cxx_builtin_include_directory: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/lib/gcc/arm-linux-gnueabihf/7.3.1/include-fixed"
  cxx_builtin_include_directory: "/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/arm-linux-gnueabihf/libc/usr/include"
  cxx_builtin_include_directory: "/usr/include"
  cxx_builtin_include_directory: "/usr/lib/python2.7/dist-packages/numpy/core/include/numpy/"

  linker_flag: "-L/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/lib"
  linker_flag: "-L/home/fabio/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gnueabihf/arm-linux-gnueabihf/lib"

  # Anticipated future default.
  # This makes GCC and Clang do what we want when called through symlinks.
  unfiltered_cxx_flag: "-no-canonical-prefixes"
  linker_flag: "-no-canonical-prefixes"

  # Make C++ compilation deterministic. Use linkstamping instead of these
  # compiler symbols.
  unfiltered_cxx_flag: "-Wno-builtin-macro-redefined"
  unfiltered_cxx_flag: "-D__DATE__=\"redacted\""
  unfiltered_cxx_flag: "-D__TIMESTAMP__=\"redacted\""
  unfiltered_cxx_flag: "-D__TIME__=\"redacted\""

  # Security hardening on by default.
  # Conservative choice; -D_FORTIFY_SOURCE=2 may be unsafe in some cases.
  # We need to undef it before redefining it as some distributions now have
  # it enabled by default.
  compiler_flag: "-U_FORTIFY_SOURCE"
  compiler_flag: "-fstack-protector"
  compiler_flag: "-fPIE"
  compiler_flag: "-std=gnu99"
  linker_flag: "-pie"
  linker_flag: "-Wl,-z,relro,-z,now"

  # Enable coloring even if there's no attached terminal. Bazel removes the
  # escape sequences if --nocolor is specified.
  # compiler_flag: "-fdiagnostics-color=always"

  # All warnings are enabled. Maybe enable -Werror as well?
  compiler_flag: "-Wall"
  compiler_flag: "-std=c++0x"
  # Enable a few more warnings that aren't part of -Wall.
  compiler_flag: "-Wunused-but-set-parameter"
  # But disable some that are problematic.
  compiler_flag: "-Wno-free-nonheap-object" # has false positives

  # Keep stack frames for debugging, even in opt mode.
  compiler_flag: "-fno-omit-frame-pointer"

  # Stamp the binary with a unique identifier.
  linker_flag: "-Wl,--build-id=md5"
  linker_flag: "-Wl,--hash-style=gnu"

  compilation_mode_flags {
    mode: DBG
    # Enable debug symbols.
    compiler_flag: "-g"
  }
  compilation_mode_flags {
    mode: OPT

    # No debug symbols.
    # Maybe we should enable https://gcc.gnu.org/wiki/DebugFission for opt or
    # even generally? However, that can't happen here, as it requires special
    # handling in Bazel.
    compiler_flag: "-g0"

    # Conservative choice for -O
    # -O3 can increase binary size and even slow down the resulting binaries.
    # Profile first and / or use FDO if you need better performance than this.
    compiler_flag: "-O2"

    # Disable assertions
    compiler_flag: "-DNDEBUG"

    # Removal of unused code and data at link time (can this increase binary size in some cases?).
    compiler_flag: "-ffunction-sections"
    compiler_flag: "-fdata-sections"
    linker_flag: "-Wl,--gc-sections"
  }
}

Launch ./configure, the only parameter to set is -march=armv7-a . Then, 

bazel build --cpu=armv7l --crosstool_top=//:toolchain --host_crosstool_top=@bazel_tools//tools/cpp:toolchain --config=opt //tensorflow/tools/pip_package:build_pip_package --verbose_failures

If you get the error:

/home/fabio/.cache/bazel/_bazel_root/fd12a6b6cbea8cd3e3322a5a0a22d119/external/nsync/BUILD:466:13: Configurable attribute "copts" doesn't match this configuration (would a default condition help?).

then, you have to edit the file /home/fabio/.cache/bazel/_bazel_root/fd12a6b6cbea8cd3e3322a5a0a22d119/external/nsync/BUILD and add the line: 

...
NSYNC_OPTS_GENERIC = select({
   ...
   ...
   "//conditions:default": [],
}) + [
...

Then, relaunch the compile process.

If you get an error about pyconfig.h not found, then you have to copy it from the directory: 

/usr/include/arm-linux-gnueabihf/python2.7/pyconfig.h

of a native arm installation in the same directory of your x86_64 machine. It's part of the python-dev package, so you have to install it via 

apt-get install python-dev

in the arm machine first.

To make the compile process successfull, you have to install the mock and the enum34 package. 

apt-get install python-pip
pip install mock

Note: the enum34 package will be automatically installed with the python-pip. Don't install (or uninstall if already installed) the python enum package, as it's a totally different package and it will make the compile process fail.

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