From a87f8954c97cf633a0100c9108764bca8c43a083 Mon Sep 17 00:00:00 2001
From: Qi Liu <liuq901@163.com>
Date: Wed, 2 Mar 2016 15:38:55 +0800
Subject: add identity layer

---
 nerv/layer/duplicate.lua | 12 ++++++------
 nerv/layer/identity.lua  | 33 +++++++++++++++++++++++++++++++++
 nerv/nn/network.lua      | 18 ++++++++++++++----
 3 files changed, 53 insertions(+), 10 deletions(-)
 create mode 100644 nerv/layer/identity.lua

diff --git a/nerv/layer/duplicate.lua b/nerv/layer/duplicate.lua
index 58758e8..fbd4a9e 100644
--- a/nerv/layer/duplicate.lua
+++ b/nerv/layer/duplicate.lua
@@ -16,13 +16,10 @@ function DuplicateLayer:__init(id, global_conf, layer_conf)
     end
 end
 
-function DuplicateLayer:init(batch_size)
+function DuplicateLayer:init()
 end
 
-function DuplicateLayer:batch_resize(batch_size)
-end
-
-function DuplicateLayer:update(bp_err, input, output)
+function DuplicateLayer:batch_resize()
 end
 
 function DuplicateLayer:propagate(input, output)
@@ -32,9 +29,12 @@ function DuplicateLayer:propagate(input, output)
     end
 end
 
-function DuplicateLayer:back_propagate(bp_err, next_bp_err, input, output)
+function DuplicateLayer:back_propagate(bp_err, next_bp_err)
     next_bp_err:copy_from(bp_err[1])
     for i = 2, #self.dim_out do
         next_bp_err:add(next_bp_err, bp_err[i], 1.0, 1.0)
     end
 end
+
+function DuplicateLayer:update()
+end
diff --git a/nerv/layer/identity.lua b/nerv/layer/identity.lua
new file mode 100644
index 0000000..dc796fb
--- /dev/null
+++ b/nerv/layer/identity.lua
@@ -0,0 +1,33 @@
+local IdentityLayer = nerv.class('nerv.IdentityLayer', 'nerv.Layer')
+
+function IdentityLayer:__init(id, global_conf, layer_conf)
+    self.id = id
+    self.dim_in = layer_conf.dim_in
+    self.dim_out = layer_conf.dim_out
+    self.gconf = global_conf
+    self:check_dim_len(1, 1)
+    if self.dim_in[1] ~= self.dim_out[1] then
+        nerv.error('mismatching dimensions of input and output')
+    end
+end
+
+function IdentityLayer:init()
+end
+
+function IdentityLayer:batch_resize()
+end
+
+function IdentityLayer:propagate(input, output)
+    output[1]:copy_from(input[1])
+end
+
+function IdentityLayer:back_propagate(bp_err, next_bp_err)
+    next_bp_err[1]:copy_from(bp_err)
+end
+
+function IdentityLayer:update()
+end
+
+function IdentityLayer:get_params()
+    return nerv.ParamRepo({})
+end
diff --git a/nerv/nn/network.lua b/nerv/nn/network.lua
index e1a9629..3cf052b 100644
--- a/nerv/nn/network.lua
+++ b/nerv/nn/network.lua
@@ -118,7 +118,7 @@ function network:init(batch_size, chunk_size)
 end
 
 function network:topsort()
-    nerv.info('Network topology sort')
+    nerv.info('network topology sort')
     local degree = {}
     for t = 1, self.chunk_size do
         degree[t] = {}
@@ -133,7 +133,7 @@ function network:topsort()
             for j = 1, #dim_out do
                 if self.output_conn[i][j] ~= nil then
                     local edge = self.output_conn[i][j]
-                    local id, _, time = edge[1], edge[2], edge[3] + t
+                    local id, time = edge[1], edge[3] + t
                     if time >= 1 and time <= self.chunk_size and id ~= 0 then
                         degree[time][id] = degree[time][id] + 1
                     end
@@ -160,7 +160,7 @@ function network:topsort()
         for j = 1, #dim_out do
             if self.output_conn[i][j] ~= nil then
                 local edge = self.output_conn[i][j]
-                local id, _, time = edge[1], edge[2], edge[3] + t
+                local id, time = edge[1], edge[3] + t
                 if time >= 1 and time <= self.chunk_size and id ~= 0 then
                     degree[time][id] = degree[time][id] - 1
                     if degree[time][id] == 0 then
@@ -178,7 +178,7 @@ function network:topsort()
 end
 
 function network:make_initial_store()
-    nerv.info('Network initing storage')
+    nerv.info('network initing storage')
 
     -- allocate memory
     local memory = {}
@@ -386,6 +386,7 @@ function network:mini_batch_init(information)
             table.insert(self.border[chunk], i)
         end
     end
+    -- copy legacy
     for t = 1 - self.delay, 0 do
         for i = 1, #self.layers do
             local _, dim_out = self.layers[i]:get_dim()
@@ -398,6 +399,7 @@ function network:mini_batch_init(information)
             end
         end
     end
+    -- flush border gradient
     for t = self.max_length + 1, self.max_length + self.delay do
         if t > self.chunk_size then
             break
@@ -419,6 +421,7 @@ function network:propagate(input, output)
         if t <= self.max_length then
             self.layers[id]:propagate(self.input[t][id], self.output[t][id], t)
         end
+        -- flush border activation
         for j = 1, #self.border[t] do
             local batch = self.border[t][j]
             local _, dim_out = self.layers[id]:get_dim()
@@ -437,6 +440,7 @@ function network:back_propagate(bp_err, next_bp_err, input, output)
     for i = #self.queue, 1, -1 do
         local t, id = self.queue[i].chunk, self.queue[i].id
         if t <= self.max_length then
+            -- flush border gradient
             for j = 1, #self.border[t] do
                 local batch = self.border[t][j]
                 local dim_in, _ = self.layers[id]:get_dim()
@@ -445,6 +449,12 @@ function network:back_propagate(bp_err, next_bp_err, input, output)
                 end
             end
             self.layers[id]:back_propagate(self.err_input[t][id], self.err_output[t][id], self.input[t][id], self.output[t][id], t)
+            if self.clip ~= nil then
+                local dim_in, _ = self.layers[id]:get_dim()
+                for j = 1, #dim_in do
+                    self.err_output[t][id][j]:clip(-self.clip, self.clip)
+                end
+            end
         end
     end
 end
-- 
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