RNN not found?

[byzhang]

When I run

   th -i main.lua -dset ptb -name srnn_sm -nhid 100 -batchsz 32 -eta 0.05

It reports the following error:

/root/torch/install/bin/luajit: main.lua:71: attempt to call global 'RNN' (a nil value)
stack traceback:
        main.lua:71: in main chunk
        [C]: in function 'dofile'
        /root/torch/install/lib/luarocks/rocks/trepl/scm-1/bin/th:145: in main chunk
        [C]: at 0x00406670

Do you know how to fix it in an easy way?