I've stuck with this problem for more than a month. In 'trainingOptions', 'gpu' is working for 'ExcutionEnvironment', but 'multi-gpu' is not working and showing the following error!
Parallel training of recurrent networks is not supported. 'ExecutionEnvironment' value in trainingOptions function must be 'auto', 'gpu', or 'cpu'.
I have two GPUs. If I check 'gpuDevice', I can see both GPUs. Also, I have Parallel Computing Toolbox, but I don't know what should I change in that toolbox in order to use the multi-gpu option.
Thank you so much in advance for your effort to help my problem!! W