local BiasLayer = nerv.class("nerv.BiasLayer", "nerv.Layer")

function BiasLayer:__init(id, global_conf, layer_conf)
    nerv.Layer.__init(self, id, global_conf, layer_conf)
    self:check_dim_len(1, 1)
    self:bind_params()
end

function BiasLayer:bind_params()
    self.bias = self:find_param("bias", self.lconf, self.gconf,
                                nerv.BiasParam,
                                {1, self.dim_out[1]})
end

function BiasLayer:init()
    if self.dim_in[1] ~= self.bias.trans:ncol() then
        nerv.error("mismatching dimensions of input and bias parameter")
    end
    if self.dim_out[1] ~= self.bias.trans:ncol() then
        nerv.error("mismatching dimensions of output and bias parameter")
    end
end

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

function BiasLayer:propagate(input, output)
    output[1]:copy_from(input[1])
    output[1]:add_row(self.bias.trans, 1.0)
end

function BiasLayer:get_params()
    return nerv.ParamRepo({self.bias}, self.loc_type)
end