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update Schedulers docs #2560

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33 changes: 33 additions & 0 deletions docs/src/guide/training/training.md
Original file line number Diff line number Diff line change
Expand Up @@ -337,6 +337,39 @@ opt_state = Flux.setup(Adam(0.02), bimodel)
Flux.adjust!(opt_state.layers.enc, 0.03)
```


## Scheduling Optimisers

In practice, it is fairly common to schedule the learning rate of an optimiser to obtain faster convergence. There are a variety of popular scheduling policies, and you can find implementations of them in [ParameterSchedulers.jl](http://fluxml.ai/ParameterSchedulers.jl/stable). The documentation for ParameterSchedulers.jl provides a more detailed overview of the different scheduling policies, and how to use them with Flux optimisers. Below, we provide a brief snippet illustrating a [cosine annealing](https://arxiv.org/pdf/1608.03983.pdf) schedule with a momentum optimiser.

First, we import ParameterSchedulers.jl and initialize a cosine annealing schedule to vary the learning rate between `1e-4` and `1e-2` every 10 epochs. We also create a new [`Momentum`](@ref Optimisers.Momentum) optimiser.
```julia
using ParameterSchedulers

opt_state = Flux.setup(Momentum(), model)
schedule = Cos(λ0 = 1e-4, λ1 = 1e-2, period = 10)
for (eta, epoch) in zip(schedule, 1:100)
Flux.adjust!(opt_state, eta)
# your training code here
end
```
`schedule` can also be indexed (e.g. `schedule(100)`) or iterated like any iterator in Julia.

ParameterSchedulers.jl schedules are stateless (they don't store their iteration state). If you want a _stateful_ schedule, you can use `ParameterSchedulers.Stateful`:
```julia
using ParameterSchedulers: Stateful, next!

schedule = Stateful(Cos(λ0 = 1e-4, λ1 = 1e-2, period = 10))
for epoch in 1:100
Flux.adjust!(opt_state, next!(schedule))
# your training code here
end
```

Finally, a scheduling function can be incorporated into the optimser's state, advanced at each gradient update step, and possibly passed to the `train!` function. See [this section](https://fluxml.ai/ParameterSchedulers.jl/stable/tutorials/optimizers/#Working-with-Flux-optimizers) of ParameterSchedulers.jl documentation for more details.

ParameterSchedulers.jl allows for many more scheduling policies including arbitrary functions, looping any function with a given period, or sequences of many schedules. See the [ParameterSchedulers.jl documentation](https://fluxml.ai/ParameterSchedulers.jl/stable) for more info.

## Freezing layer parameters

To completely disable training of some part of the model, use [`freeze!`](@ref Flux.freeze!).
Expand Down
32 changes: 1 addition & 31 deletions docs/src/reference/training/optimisers.md
Original file line number Diff line number Diff line change
Expand Up @@ -67,36 +67,6 @@ It is possible to compose optimisers for some added flexibility.
Optimisers.OptimiserChain
```

## Scheduling Optimisers

In practice, it is fairly common to schedule the learning rate of an optimiser to obtain faster convergence. There are a variety of popular scheduling policies, and you can find implementations of them in [ParameterSchedulers.jl](http://fluxml.ai/ParameterSchedulers.jl/stable). The documentation for ParameterSchedulers.jl provides a more detailed overview of the different scheduling policies, and how to use them with Flux optimisers. Below, we provide a brief snippet illustrating a [cosine annealing](https://arxiv.org/pdf/1608.03983.pdf) schedule with a momentum optimiser.

First, we import ParameterSchedulers.jl and initialize a cosine annealing schedule to vary the learning rate between `1e-4` and `1e-2` every 10 steps. We also create a new [`Momentum`](@ref Optimisers.Momentum) optimiser.
```julia
using ParameterSchedulers

opt = Momentum()
schedule = Cos(λ0 = 1e-4, λ1 = 1e-2, period = 10)
for (eta, epoch) in zip(schedule, 1:100)
opt.eta = eta
# your training code here
end
```
`schedule` can also be indexed (e.g. `schedule(100)`) or iterated like any iterator in Julia.

ParameterSchedulers.jl schedules are stateless (they don't store their iteration state). If you want a _stateful_ schedule, you can use `ParameterSchedulers.Stateful`:
```julia
using ParameterSchedulers: Stateful, next!

schedule = Stateful(Cos(λ0 = 1e-4, λ1 = 1e-2, period = 10))
for epoch in 1:100
opt.eta = next!(schedule)
# your training code here
end
```

ParameterSchedulers.jl allows for many more scheduling policies including arbitrary functions, looping any function with a given period, or sequences of many schedules. See the ParameterSchedulers.jl documentation for more info.

## Decays

Similar to optimisers, Flux also defines some simple decays that can be used in conjunction with other optimisers, or standalone.
Expand All @@ -111,7 +81,7 @@ Optimisers.WeightDecay
Gradient clipping is useful for training recurrent neural networks, which have a tendency to suffer from the exploding gradient problem. An example usage is

```julia
opt = OptimiserChain(ClipValue(1e-3), Adam(1e-3))
opt = OptimiserChain(ClipGrad(1e-3), Adam(1e-3))
```

```@docs
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