In torch, we can share parameters between two nets like this,
local r1 = nn.Recurrent(
        opt.embeddingSize,
        cnn,
        h2h,
        nn.Identity(),
        opt.sampleSeqLength)
local r2 = nn.Recurrent(
        opt.embeddingSize,
        cnn:clone('weight','bias','gradWeight','gradBias'),
        h2h:clone('weight','bias','gradWeight','gradBias'),
        nn.Identity(),
        opt.sampleSeqLength)

so, how to share weights between two nets in pytorch?