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path: root/nerv/examples/lmptb/rnn/layers/gate_fff.lua
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local GateFFFLayer = nerv.class('nerv.GateFFFLayer', 'nerv.Layer')

function GateFFFLayer:__init(id, global_conf, layer_conf)
    self.id = id
    self.ltp = layer_conf.ltp
    self.bp = layer_conf.bp
    self.dim_in = layer_conf.dim_in
    self.dim_out = layer_conf.dim_out
    self.gconf = global_conf
    self:check_dim_len(1, 1) -- exactly one input and one output
end

function GateFFFLayer:init(batch_size)
    if self.ltp.trans:ncol() ~= self.bp.trans:ncol() then
        nerv.error("mismatching dimensions of linear transform and bias paramter")
    end
    if self.dim_in[1] ~= self.ltp.trans:nrow() then
        nerv.error("mismatching dimensions of linear transform parameter and input")
    end
    if self.dim_out[1] ~= self.ltp.trans:ncol() then
        nerv.error("mismatching dimensions of linear transform parameter and output")
    end
    self.ltp_grad = self.ltp.trans:create()
    self.ltp:train_init()
    self.bp:train_init()
end

function GateFFFLayer:batch_resize(batch_size)
    -- do nothing
end

function GateFFFLayer:update(bp_err, input, output)
    if self.direct_update == true then
        local gconf = self.gconf
        if gconf.momentum > 0 then
            self.ltp.correction:mul(input[1], bp_err[1], 1.0, gconf.momentum, 'T', 'N')
            self.bp.correction:add(self.bp.correction, bp_err[1]:colsum(), gconf.momentum, 1)
            -- momentum gain
            local mmt_gain = 1.0 / (1.0 - gconf.momentum)
            local n = self.gconf.batch_size * mmt_gain
            -- perform update
            self.ltp.trans:add(self.ltp.trans, self.ltp.correction, 1.0 - gconf.lrate * gconf.wcost / gconf.batch_size, - gconf.lrate / n)
            self.bp.trans:add(self.bp.trans, self.bp.correction, 1.0 - gconf.lrate * gconf.wcost / gconf.batch_size, - gconf.lrate / n)
        else
            self.ltp.trans:mul(input[1], bp_err[1], - gconf.lrate / gconf.batch_size, 1.0 - gconf.lrate * gconf.wcost / gconf.batch_size, 'T', 'N')
            self.bp.trans:add(self.bp.trans, bp_err[1]:colsum(), 1.0 - gconf.lrate * gconf.wcost / gconf.batch_size, - gconf.lrate / gconf.batch_size)
        end
    else
        self.ltp:update_by_err_input(bp_err[1], input[1])
        self.bp:update_by_gradient(bp_err[1]:colsum())
    end
end

function GateFFFLayer:propagate(input, output)
    -- apply linear transform
    output[1]:mul(input[1], self.ltp.trans, 1.0, 0.0, 'N', 'N')
    -- add bias
    output[1]:add_row(self.bp.trans, 1.0)
end

function GateFFFLayer:back_propagate(bp_err, next_bp_err, input, output)
    next_bp_err[1]:mul(bp_err[1], self.ltp.trans, 1.0, 0.0, 'N', 'T')
end

function GateFFFLayer:get_params()
    return nerv.ParamRepo({self.ltp, self.bp})
end