From 86f25ca3f68d2d80c3e14830dff5a78467d9b7f4 Mon Sep 17 00:00:00 2001
From: Moelf <jerryling315@gmail.com>
Date: Tue, 16 Jun 2020 16:37:10 -0700
Subject: [PATCH 1/3] add Flux.skip()

---
 src/optimise/train.jl | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/src/optimise/train.jl b/src/optimise/train.jl
index 7e7b516c9b..74b2200eb0 100644
--- a/src/optimise/train.jl
+++ b/src/optimise/train.jl
@@ -37,6 +37,26 @@ call(f, xs...) = f(xs...)
 runall(f) = f
 runall(fs::AbstractVector) = () -> foreach(call, fs)
 
+struct SkipException <: Exception end
+
+"""
+    skip()
+
+Call `Flux.skip()` in a callback to indicate when a callback condition is met.
+This will trigger the train loop to skip the current data point and not update with the calculated gradient.
+
+# Examples
+```julia
+cb = function ()
+  loss() > 1e7 && Flux.skip()
+end
+```
+"""
+function skip()
+  throw(SkipException())
+end
+
+
 struct StopException <: Exception end
 
 """
@@ -93,6 +113,8 @@ function train!(loss, ps, data, opt; cb = () -> ())
     catch ex
       if ex isa StopException
         break
+      elseif ex isa SkipException
+        continue
       else
         rethrow(ex)
       end

From 857566d8c94f355a494db8e8f8aaa799cc988c8a Mon Sep 17 00:00:00 2001
From: Moelf <proton@jling.dev>
Date: Thu, 20 Aug 2020 14:41:05 -0400
Subject: [PATCH 2/3] add Flux.skip() test and docs

---
 docs/src/utilities.md    |  1 +
 src/Flux.jl              |  1 +
 src/optimise/Optimise.jl |  2 +-
 test/optimise.jl         | 10 +++++++++-
 4 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/docs/src/utilities.md b/docs/src/utilities.md
index 7986ec238d..95ef098ea5 100644
--- a/docs/src/utilities.md
+++ b/docs/src/utilities.md
@@ -46,4 +46,5 @@ Flux.destructure
 ```@docs
 Flux.throttle
 Flux.stop
+Flux.skip
 ```
diff --git a/src/Flux.jl b/src/Flux.jl
index c28a7d3637..8d485ecfbd 100644
--- a/src/Flux.jl
+++ b/src/Flux.jl
@@ -19,6 +19,7 @@ export Chain, Dense, Maxout, RNN, LSTM, GRU, SamePad, Conv, CrossCor, ConvTransp
 include("optimise/Optimise.jl")
 using .Optimise
 using .Optimise: @epochs
+using .Optimise: skip
 export Descent, ADAM, Momentum, Nesterov, RMSProp,
   ADAGrad, AdaMax, ADADelta, AMSGrad, NADAM,
   ADAMW, RADAM, InvDecay, ExpDecay, WeightDecay,
diff --git a/src/optimise/Optimise.jl b/src/optimise/Optimise.jl
index 0f5e644f0d..37672706d2 100644
--- a/src/optimise/Optimise.jl
+++ b/src/optimise/Optimise.jl
@@ -5,7 +5,7 @@ using LinearAlgebra
 export train!, update!,
 	Descent, ADAM, Momentum, Nesterov, RMSProp,
 	ADAGrad, AdaMax, ADADelta, AMSGrad, NADAM, ADAMW,RADAM, 
-	InvDecay, ExpDecay, WeightDecay, stop, Optimiser,
+	InvDecay, ExpDecay, WeightDecay, stop, skip, Optimiser,
 	ClipValue, ClipNorm
 
 include("optimisers.jl")
diff --git a/test/optimise.jl b/test/optimise.jl
index 8a338bcb66..5198444a9a 100644
--- a/test/optimise.jl
+++ b/test/optimise.jl
@@ -39,6 +39,14 @@ end
 @testset "Training Loop" begin
   i = 0
   l = 1
+  Flux.train!(
+              () -> (sleep(0.1); Flux.skip(); i+=1),
+              (),
+              Iterators.repeated((), 10),
+              Descent()
+             )
+
+  @test i==0 #all skipped
 
   Flux.train!(() -> (sleep(0.1); i += 1; l),
               (),
@@ -110,4 +118,4 @@ end
     @test all(w̄_value .<= 1)
     w̄_norm = Optimise.apply!(ClipNorm(1.0), w, copy(w̄))
     @test norm(w̄_norm) <= 1
-end
\ No newline at end of file
+end

From 56fafa695151fcac2127c96493885b2b2c81a63c Mon Sep 17 00:00:00 2001
From: Moelf <proton@jling.dev>
Date: Fri, 9 Oct 2020 10:50:47 -0400
Subject: [PATCH 3/3] more test

---
 test/optimise.jl | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/test/optimise.jl b/test/optimise.jl
index e868d6a927..4d90ec8e94 100644
--- a/test/optimise.jl
+++ b/test/optimise.jl
@@ -55,6 +55,16 @@ end
 
   @test i==0 #all skipped
 
+  Flux.train!(
+              () -> (sleep(0.1); i==8 && Flux.skip(); i+=1),
+              (),
+              Iterators.repeated((), 10),
+              Descent()
+             )
+
+  @test i==8 #skip after i hit 8
+
+  i = 0
   Flux.train!(() -> (sleep(0.1); i += 1; l),
               (),
               Iterators.repeated((), 100),