Multi-GPU Support

[Former user]

When I tried to use two GPUs, error occurred as follows:

Error using bcnn_train_dag>(spmd) (line 109)
Error detected on workers 1 2.

Error in bcnn_train_dag (line 109)
    spmd

Error in imdb_bcnn_train_dag (line 160)
    [net, info] = bcnn_train_dag(net, imdb, fn_train, fn_val, opts.train) ;

Error in run_experiments_bcnn_train (line 79)
          imdb_bcnn_train_dag(imdb, opts);

Caused by:
    Error using vl_argparse (line 46)
    Parameter-value pair expected (missing value?).
    Error using vl_argparse (line 46)
    Parameter-value pair expected (missing value?).