Can one of the admins verify this patch?

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I added my email to my profile, hope this helps the CLA check.

CLAs look good, thanks!

I would love to have this in contrib/ can you move the files there? Then we can merge.

Is this being actively worked on? If not, I'd be glad to give this a go. It would be very useful in getting tensorflow building on clusters with old versions of glibc and the like.

Can one of the admins verify this patch?

@rbharath Hi, sorry for the delay, I've been caught up in another project over the past few weeks, I was hoping to get back to this sooner. Your help is most welcome, thanks a lot! Please feel free to ping me if something is not clear in the code, and I'll try to come back to this within the next couple of weeks.

@ageron: Glad to be useful! I'll give this a shot. I'm no cmake expert, but hopefully I can make enough progress to get somewhere useful.

@ageron I checked out this PR and tried to get tensorflow to build on my machine using cmake (Ubuntu 12.04 with glic 2.15, gcc 4.9.1, cmake 3.5). I made it a ways, but the build crashes when trying to compile the re2 library:

libbenchmark.a(benchmark.cc.o): In function `_Z8RunBenchPN7testing9BenchmarkEii.part.2':
benchmark.cc:(.text+0x4f): undefined reference to `clock_gettime'
benchmark.cc:(.text+0x149): undefined reference to `clock_gettime'
benchmark.cc:(.text+0x195): undefined reference to `clock_gettime'
benchmark.cc:(.text+0x377): undefined reference to `clock_gettime'
libbenchmark.a(benchmark.cc.o): In function `StopBenchmarkTiming()':
benchmark.cc:(.text+0x47a): undefined reference to `clock_gettime'
libbenchmark.a(benchmark.cc.o):benchmark.cc:(.text+0x4da): more undefined references to     `clock_gettime' follow

The cmake code uses the command ExternalProject to internally download re2 and build it. The failure above is due the linking flag '-lrt' being missing (the rt library was merged into glibc from 2.17 onwards, but I have an old version of glibc locally). The strange thing here though is that I can clone re2 from github manually and get it to build outside of cmake, so there's some arcana about the cmake build that's confusing me. Do you have any thoughts?

@rbharath That's really weird, I'm looking into it. Also, I'm moving cmake to tensorflow/contrib/cmake, as requested, and catching up to all the changes that have happened in the last few weeks. I'll try to finish by tomorrow.

@rbharath I updated the code to move cmake/ to tensorflow/contrib/cmake/, and I updated to the latest upstream commit and fixed a couple issues. The code builds and runs fine on my MacOSX machine (tf_tutorials_example_trainer), but I just tried to build it on an Ubuntu VM, and it failed with similar issues as you (linkage errors). Adding the following code just after "find_package(Threads)" in tensorflow/contrib/cmake/CMakeLists.txt fixed the build problem:

IF (UNIX)
    LINK_LIBRARIES(${CMAKE_THREAD_LIBS_INIT} ${CMAKE_DL_LIBS} -lm -lrt)
ENDIF (UNIX)

Now it builds all the way to the end, but I get a segfault when I run tf_tutorials_example_trainer on Ubuntu. I'm investigating why, here's a quick dbg session:
debug_tf.txt

Before building TensorFlow, I installed a few packages:

sudo apt-get install build-essential
sudo apt-get install zlib1g-dev

I also built and installed Protobuf 3 from the source in google/protobuf (I followed the instructions in google/protobuf/cmake/README.md, without gmock)
As I installed it in a non-standard directory, I added the following options to the cmake commands when building TensorFlow:

-DPROTOBUF_PROTOC_EXECUTABLE=[...]/install/bin/protoc
-DPROTOBUF_INCLUDE_DIR=[...]/install/include
-DPROTOBUF_PROTOC_LIBRARY=[...]/install/lib/libprotoc.a
-DPROTOBUF_LIBRARY=[...]/install/lib/libprotobuf.a

@martinwicke Hi Martin, I moved the cmake/ directory to tensorflow/contrib/cmake, and caught up to the latest upstream commit.

Thanks @ageron! I'm merging this for the greater good, even if it's still broken.

Merged. Is the segfault the same problem you had in your first version?

@ageron, @martinwicke I managed to get around the linking issues in re2 (The fix suggested above didn't quite work for me, but something close did. However, I'm now running into a make error when compiling tf_core_kernels

/home/rbharath/tensorflow/tensorflow/core/kernels/matrix_solve_ls_op.cc: In member function ‘void tensorflow::MatrixSolveLsOp<Scalar, SupportsBatchOperationT>::ComputeMatrix(tensorflow::OpKernelContext*, const typename tensorflow::BinaryLinearAlgebraOp<Scalar, SupportsBatchOperationT>::ConstMatrixMap&, const typename tensorflow::BinaryLinearAlgebraOp<Scalar, SupportsBatchOperationT>::ConstMatrixMap&,   typename tensorflow::BinaryLinearAlgebraOp<Scalar, SupportsBatchOperationT>::MatrixMap*)’:
/home/rbharath/tensorflow/tensorflow/core/kernels/matrix_solve_ls_op.cc:111:41: error: ‘Matrix’ is not a class, namespace, or enumeration
           (Scalar(l2_regularizer) * Matrix::Ones(cols, 1)).asDiagonal();
                                     ^
/home/rbharath/tensorflow/tensorflow/core/kernels/matrix_solve_ls_op.cc:131:41: error: ‘Matrix’ is not a class, namespace, or enumeration
           (Scalar(l2_regularizer) * Matrix::Ones(rows, 1)).asDiagonal();
                                     ^
make[2]: ***   [CMakeFiles/tf_core_kernels.dir/home/rbharath/tensorflow/tensorflow/core/kernels/matrix_solve_ls_op.cc.o] Error 1
make[1]: *** [CMakeFiles/tf_core_kernels.dir/all] Error 2
make: *** [all] Error 2

Do you have any thoughts on possible fixes?

I think your version of gcc doesn't know how to parse

"using typename BinaryLinearAlgebraOp<Scalar, SupportsBatchOperationT>::Matrix;" higher in the file -- my suggestion is to either upgrade your gcc and/or maybe downgrade our code to use less sophisticated C++ features :)

@vrv Thanks for the pointer!

@martinwicke I've made the changes required to get CMake to compile on ubuntu in PR #1309. Could you take a quick look?

@ageron: Unfortunately, I'm also seeing a segfault in my compiled version. I'll do some digging on my end as well to see if I can figure something out.

I'm closing this PR (it's merged). Feel free to continue using it as a message board, or move to #1309.