add tanh activation

nn.lua

@@ -16,6 +16,7 @@ local print = print
 local remove = table.remove
 local sin = math.sin
 local sqrt = math.sqrt
+local tanh = math.tanh
 local tostring = tostring
 local uniform = math.random
 local unpack = table.unpack or unpack
@@ -293,6 +294,7 @@ local Merge = Layer:extend()
 local Relu = Layer:extend()
 local Gelu = Layer:extend()
 local Cos = Layer:extend()
+local Tanh = Layer:extend()
 local Dense = Layer:extend()
 local Softmax = Layer:extend()
 local Embed = Layer:extend()
@@ -515,6 +517,28 @@ function Cos:forward(X)
     return Y
 end
 
+function Tanh:init()
+    Layer.init(self, "Tanh")
+end
+
+function Tanh:reset_cache(bs)
+    self.bs = bs
+
+    self.cache  = cache(bs, self.shape_out)
+    self.dcache = cache(bs, self.shape_in)
+end
+
+function Tanh:forward(X)
+    local bs = checkshape(X, self.shape_in)
+    if bs ~= self.bs then self:reset_cache(bs) end
+    local Y = self.cache
+
+    for i = 1, #X do Y[i] = tanh(X[i]) end
+
+    checkshape(Y, self.shape_out)
+    return Y
+end
+
 function Dense:init(dim)
     Layer.init(self, "Dense")
     assert(type(dim) == "number")
@@ -813,6 +837,7 @@ return {
     Relu        = Relu,
     Gelu        = Gelu,
     Cos         = Cos,
+    Tanh        = Tanh,
     Dense       = Dense,
     Softmax     = Softmax,
     Embed       = Embed,