error on matlab 2017a, ubunu

[sjsy]

Hi!
System configuration:

• OS: Ubuntu 16.04
• Matlab: 20017a
• gcc version: 5.4.0

MatConvNet error:

>> cnn_mnist_experiments

parameter memory| 2MB (4.3e+05 parameters)|
data memory|14MB (for batch size 100)|
... (table omitted)
train: epoch 01: 1/600:Invalid MEX-file '/home/user/Code/matlab/matconvnet-1.0-beta24/matlab/mex/vl_nnconv.mexa64':
Missing symbol 'ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE4swapERS4' required by
'/home/user/Code/matlab/matconvnet-1.0-beta24/matlab/mex/vl_nnconv.mexa64'
Missing symbol '_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE9_M_appendEPKcm' required by
'/home/user/Code/matlab/matconvnet-1.0-beta24/matlab/mex/vl_nnconv.mexa64'
Missing symbol 'ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE9_M_assignERKS4' required by
'/home/user/Code/matlab/matconvnet-1.0-beta24/matlab/mex/vl_nnconv.mexa64'
Missing symbol '_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE9_M_createERmm' required by
'/home/user/Code/matlab/matconvnet-1.0-beta24/matlab/mex/vl_nnconv.mexa64'.

Error in vl_simplenn (line 300)
res(i+1).x = vl_nnconv(res(i).x, l.weights{1}, l.weights{2}, ...

Error in cnn_train>processEpoch (line 350)
res = vl_simplenn(net, im, dzdy, res, ...

Error in cnn_train (line 150)
[net, state] = processEpoch(net, state, params, 'train') ;

Error in cnn_mnist (line 54)
[net, info] = trainfn(net, imdb, getBatch(opts), ...

Error in cnn_mnist_experiments (line 4)
[net_bn, info_bn] = cnn_mnist(...

Any help?
Thanks.

[daa233]

I had the same problem with ubuntu 16.04, matlab 2017a, g++/gcc 5.4 and without GPU. Refering to this: #937, I added the following content in ~/.bashrc and fixed the problem.

export LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libstdc++.so.6:/usr/lib/x86_64-linux-gnu/libprotobuf.so.9

By the way, don't forget to execute source ~/.bashrc in the terminal to make the changes work immediately.

[agpoyraz]

Gcc 5.4 is not supported for compiling(vl_nncompilenn) for matlab 2017a. You have to use 4.9 .. version gcc

[ankitkp4056]

Problem

Ubuntu 16.04 has [g++/gcc-5] as the default compiler but "Matlab 2017a" supports upto [g++/gcc - 4.9 ] only.

Solution-1

You could change your ~/.bashrc file to make [g++/gcc-4.9] as your default compiler.
simply follow the steps mentioned by DAA233 .

but this is not a very wise choice as some day, some other program just might not be compatible with [g++/gcc-4.9] and you will end up juggling the contents of your ~/.bashrc file.

Solution-2

You could set priority to use [g++/gcc-4.9] before [g++/gcc-5] .

Follow these steps:

--> Make sure gcc-4.9 and g++-4.9 are installed.
~$ sudo apt-get install gcc-4.9 g++-4.9

--> Set "priority=100" for gcc-4.9 and "priority=50" for gcc-5.
~$ sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.9 100
~$ sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-5.0 50

--> Set "priority=100" for g++-4.9 and "priority=50" for g++-5.
~$ sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.9 100
~$ sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-5.0 50

--> Verify the priority settings using:
~$ update-alternatives --query gcc

Name: gcc
Link: /usr/bin/gcc
Status: auto
Best: /usr/bin/gcc-4.9
Value: /usr/bin/gcc-4.9

Alternative: /usr/bin/gcc-4.9
Priority: 100

Alternative: /usr/bin/gcc-5
Priority: 50

~$ update-alternatives --query g++

Name: g++
Link: /usr/bin/g++
Status: auto
Best: /usr/bin/g++-4.9
Value: /usr/bin/g++-4.9

Alternative: /usr/bin/g++-4.9
Priority: 100

Alternative: /usr/bin/g++-5
Priority: 50

Make sure you have your compilers in /usr/bin/ directory.
PS: You will need to recompile matconvnet after this .

EDIT: "corrected command for g++" (...thanks Haini)

[Haini]

For g++ alternatives one should change the compiler names from

--> Set "priority=100" for g++-4.9 and "priority=50" for g++-5.
~$ sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/g++-4.9 100
~$ sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/g++-5.0 50

to
~$ sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.9 100
~$ sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-5.0 50

At least that would make sense, as we later query for g++ too.
As a sidenote: On Ubuntu the path for the compiler version 5.0 is just /usr/bin/g++-5.

[ankitkp4056]

Thanks Haini...I made the changes.

[mcimpoi]

Following matconvnet documentation setting up the mex compiler seems to fix the problem:
mex -setup C++