MXNet needs to be built so that the `lib/libmxnet.so`

is available, which can be done by:

cd .. make

The pre-trained `Inception-BN`

should be downloaded to obtain the symbol and network parameters.

./get_inception_model.sh

This data will be saved in the `./data`

folder:

./data/ ├── cat.png ├── Inception-BN-0126.params ├── Inception-BN-symbol.json └── synset.txt

####Sample usage

Run the demo script from the command-line without invoking Matlab GUI:

matlab -nodisplay -nojvm -nosplash -nodesktop -r "run('./demo.m'), exit(0);"

or the script may be run from the Matlab GUI as usual.

The script has the following components:

Load model

model = mxnet.model; model.load('data/Inception-BN', 126);

Load data and normalise. Here we assume a fixed value of 120 as ‘mean image’:

img = single(imresize(imread('./data/cat.png'), [224 224])) - 120;

Get prediction:

pred = model.forward(img);

Do feature extraction on CPU or GPU 0:

feas = model.forward(img, {'max_pool_5b_pool', 'global_pool', 'fc1'}); % CPU mode feas = model.forward(img, 'gpu', 0, {'max_pool_5b_pool', 'global_pool', 'fc1'}); % GPU mode

See demo.m for more details

We use `loadlibrary`

to load mxnet library directly into Matlab and `calllib`

to call MXNet functions. Note that Matlab uses the column-major to store N-dim arrays while and MXNet uses the row-major. So assume we create an array in Matlab with

X = zeros([2,3,4,5]);

If we pass the memory of `X`

into MXNet, then the correct shape will be `[5,4,3,2]`

in MXNet. When processing images, MXNet assumes the data layout is

batchSize x channel x width x height

while in Matlab we often store images in

width x height x channel x batchSize

So we should permute the dimensions by `X = permute(X, [2, 1, 3, 4])`

before passing `X`

into MXNet.

You may get the error

`GLIBCXX_x.x.xx`

is not found. Such as on Ubuntu 14.04:> In loadlibrary (line 359) Error using loadlibrary (line 447) There was an error loading the library "/home/muli/work/mxnet/lib/libmxnet.so" /usr/local/MATLAB/R2015a/bin/glnxa64/../../sys/os/glnxa64/libstdc++.so.6: version `GLIBCXX_3.4.18' not found (required by /home/muli/work/mxnet/lib/libmxnet.so) Caused by: Error using loaddefinedlibrary /usr/local/MATLAB/R2015a/bin/glnxa64/../../sys/os/glnxa64/libstdc++.so.6: version `GLIBCXX_3.4.18' not found (required by /home/muli/work/mxnet/lib/libmxnet.so)

One way to fix it is to link `MATLAB_ROOT/sys/os/glnxa64/libstdc++.so.6` to your system's `libstdc++`. For example

muli@ghc:/usr/local/MATLAB/R2015a/sys/os/glnxa64$ sudo rm -r libstdc++.so.6 muli@ghc:/usr/local/MATLAB/R2015a/sys/os/glnxa64$ sudo ln -s /usr/lib/x86_64-linux-gnu/ libstdc++.so.6.0.19 libstdc++.so.6

Matlab binding has been tested with the following version:

`R2016b (9.1.0.441655) 64-bit (glnxa64)`