From 88fa163c95231969a0898470a11c72dc65d4ca2e Mon Sep 17 00:00:00 2001
From: ylxdzsw <ylxdzsw@gmail.com>
Date: Fri, 21 Jul 2017 16:31:12 +0800
Subject: [PATCH 1/2] throttle

---
 src/training.jl | 45 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 43 insertions(+), 2 deletions(-)

diff --git a/src/training.jl b/src/training.jl
index 62a34c46..3632eb82 100644
--- a/src/training.jl
+++ b/src/training.jl
@@ -25,18 +25,59 @@ macro cb(ex, t, f)
   end)
 end
 
+"""
+Returns a function that when invoked, will only be triggered at most once
+during `timeout` seconds. Normally, the throttled function will run
+as much as it can, without ever going more than once per `wait` duration;
+but if you'd like to disable the execution on the leading edge, pass
+`leading=false`. To enable execution on the trailing edge, ditto.
+"""
+function throttle(f, timeout; leading=true, trailing=false)
+  cooldown = true
+  later = nothing
+
+  function throttled(args...; kwargs...)
+    yield()
+
+    if cooldown
+      if leading
+        f(args...; kwargs...)
+      else
+        later = () -> f(args...; kwargs...)
+      end
+
+      cooldown = false
+      @schedule try
+        while (sleep(timeout); later != nothing)
+          later()
+          later = nothing
+        end
+      finally
+        cooldown = true
+      end
+    elseif trailing
+      later = () -> f(args...; kwargs...)
+    end
+
+    nothing
+  end
+end
+
 function train!(m, train; cb = [],
                 epoch = 1, η = 0.1, loss = mse)
+    callback = throttle(()->foreach(f -> f(), cb), 5)
+
     @progress for e in 1:epoch
       info("Epoch $e")
-      @cb for (x, y) in train
+      for (x, y) in train
         x, y = mapt(tobatch, (x, y))
         ŷ = m(x)
         any(isnan, ŷ) && error("NaN")
         Δ = back!(loss, 1, ŷ, y)
         back!(m, Δ, x)
         update!(m, η)
-      end 5 foreach(f -> f(), cb)
+        callback()
+      end
     end
     return m
 end

From cce1a2a73e4155a6233822380c26d6c063f72de1 Mon Sep 17 00:00:00 2001
From: ylxdzsw <ylxdzsw@gmail.com>
Date: Wed, 26 Jul 2017 09:57:20 +0800
Subject: [PATCH 2/2] add tests for throttle

---
 test/runtests.jl |  1 +
 test/throttle.jl | 49 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)
 create mode 100644 test/throttle.jl

diff --git a/test/runtests.jl b/test/runtests.jl
index 655d924a..7128e13b 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -18,6 +18,7 @@ include("backend/common.jl")
 include("basic.jl")
 include("recurrent.jl")
 include("optimizer.jl")
+include("throttle.jl")
 
 @tfonly include("backend/tensorflow.jl")
 @mxonly include("backend/mxnet.jl")
diff --git a/test/throttle.jl b/test/throttle.jl
new file mode 100644
index 00000000..d3dcd925
--- /dev/null
+++ b/test/throttle.jl
@@ -0,0 +1,49 @@
+using Flux.throttle
+
+@testset "throttle" begin
+  @testset "default behaviour" begin
+    a = []
+    f = throttle(()->push!(a, now()), 1, leading=true, trailing=false)
+    f()
+    f()
+    f()
+    sleep(1.01)
+    @test length(a) == 1
+  end
+
+  @testset "leading behaviour" begin
+    a = []
+    f = throttle(()->push!(a, now()), 1, leading=true, trailing=false)
+    f()
+    @test length(a) == 1
+    f()
+    @test length(a) == 1
+    sleep(1.01)
+    f()
+    @test length(a) == 2
+  end
+
+  @testset "trailing behaviour" begin
+    a = []
+    f = throttle(()->push!(a, now()), 1, leading=false, trailing=true)
+    f()
+    @test length(a) == 0
+    f()
+    @test length(a) == 0
+    sleep(1.01)
+    @test length(a) == 1
+  end
+
+  @testset "arguments" begin
+    a = []
+    f = throttle((x)->push!(a, x), 1, leading=true, trailing=true)
+    f(1)
+    @test a == [1]
+    f(2)
+    @test a == [1]
+    f(3)
+    @test a == [1]
+    sleep(1.01)
+    @test a == [1, 3]
+  end
+end