Improve docs, revamp checks (#449)

Author: gdalle

DifferentiationInterface/README.md

@@ -17,10 +17,7 @@ An interface to various automatic differentiation (AD) backends in Julia.
 
 ## Goal
 
-This package provides a backend-agnostic syntax to differentiate functions of the following types:
-
-- _one-argument functions_ (allocating): `f(x) = y`
-- _two-argument functions_ (mutating): `f!(y, x) = nothing`
+This package provides a unified syntax to differentiate functions.
 
 ## Features
 

DifferentiationInterface/docs/src/api.md

@@ -103,8 +103,7 @@ value_gradient_and_hessian!
 
 ```@docs
 check_available
-check_twoarg
-check_hessian
+check_inplace
 DifferentiationInterface.outer
 DifferentiationInterface.inner
 ```

DifferentiationInterface/docs/src/backends.md

@@ -5,8 +5,9 @@ This page is about the latter, check out [that page](@ref "Operators") to learn
 
 ## List of backends
 
-We support all dense backend choices from [ADTypes.jl](https://github.com/SciML/ADTypes.jl):
+We support the following dense backend choices from [ADTypes.jl](https://github.com/SciML/ADTypes.jl):
 
+- [`AutoChainRules`](@extref ADTypes.AutoChainRules)
 - [`AutoDiffractor`](@extref ADTypes.AutoDiffractor)
 - [`AutoEnzyme`](@extref ADTypes.AutoEnzyme)
 - [`AutoFastDifferentiation`](@extref ADTypes.AutoFastDifferentiation)
@@ -37,11 +38,17 @@ We strongly recommend that users upgrade to Julia 1.10 or above, where all backe
 
 ## Features
 
+Given a backend object, you can use:
+
+- [`check_available`](@ref) to know whether the required AD package is loaded
+- [`check_inplace`](@ref) to know whether the backend supports in-place functions (all backends support out-of-place functions)
+
 ```@setup backends
 using ADTypes
 using DifferentiationInterface
 import Markdown
 
+import ChainRulesCore
 import Diffractor
 import Enzyme
 import FastDifferentiation
@@ -56,6 +63,7 @@ import Tracker
 import Zygote
 
 backend_examples = [
+    AutoChainRules(; ruleconfig=Zygote.ZygoteRuleConfig()),
     AutoDiffractor(),
     AutoEnzyme(),
     AutoFastDifferentiation(),
@@ -72,17 +80,16 @@ backend_examples = [
 
 checkmark(x::Bool) = x ? '✅' : '❌'
 unicode_check_available(backend) = checkmark(check_available(backend))
-unicode_check_hessian(backend)   = checkmark(check_hessian(backend; verbose=false))
-unicode_check_twoarg(backend)    = checkmark(check_twoarg(backend))
+unicode_check_inplace(backend)    = checkmark(check_inplace(backend))
 
 io = IOBuffer()
 
 # Table header 
-println(io, "| Backend | Availability | Two-argument functions | Hessian support |")
-println(io, "|:--------|:------------:|:----------------------:|:---------------:|")
+println(io, "| Backend | Availability | In-place functions |")
+println(io, "|:--------|:------------:|:----------------------:|")
 
 for b in backend_examples
-    join(io, ["`$(nameof(typeof(b)))`", unicode_check_available(b), unicode_check_twoarg(b), unicode_check_hessian(b)], '|')
+    join(io, ["`$(nameof(typeof(b)))`", unicode_check_available(b), unicode_check_inplace(b)], '|')
     println(io, '|' )
 end
 backend_table = Markdown.parse(String(take!(io)))
@@ -92,21 +99,6 @@ backend_table = Markdown.parse(String(take!(io)))
 backend_table #hide
 ```
 
-### Availability
-
-You can use [`check_available`](@ref) to verify whether a given backend is loaded.
-
-### Support for two-argument functions
-
-All backends are compatible with one-argument functions `f(x) = y`.
-Only some are compatible with two-argument functions `f!(y, x) = nothing`.
-You can use [`check_twoarg`](@ref) to verify this compatibility.
-
-### Support for Hessian
-
-Only some backends are able to compute Hessians.
-You can use [`check_hessian`](@ref) to verify this feature (beware that it will try to compute a small Hessian, so it is not instantaneous like the other checks).
-
 ## Backend switch
 
 The wrapper [`DifferentiateWith`](@ref) allows you to switch between backends.

DifferentiationInterface/docs/src/dev_guide.md

@@ -24,8 +24,7 @@ Most operators have 4 variants, which look like this in the first order: `operat
 ## New operator
 
 To implement a new operator for an existing backend, you need to write 5 methods: 1 for [preparation](@ref Preparation) and 4 corresponding to the variants of the operator (see above).
-In some cases, a subset of those methods will be enough, but most of the time, forgetting one will trigger errors.
-For first-order operators, you may also want to support [two-argument functions](@ref "Mutation and signatures"), which requires another 5 methods (defined on `f!` instead of `f`).
+For first-order operators, you may also want to support [in-place functions](@ref "Mutation and signatures"), which requires another 5 methods (defined on `f!` instead of `f`).
 
 The method `prepare_operator` must output an `extras` object of the correct type.
 For instance, `prepare_gradient(f, backend, x)` must return a [`DifferentiationInterface.GradientExtras`](@ref).
@@ -40,7 +39,7 @@ Your AD package needs to be registered first.
 ### Core code
 
 In the main package, you should define a new struct `SuperDiffBackend` which subtypes [`ADTypes.AbstractADType`](@extref ADTypes), and endow it with the fields you need to parametrize your differentiation routines.
-You also have to define [`ADTypes.mode`](@extref) and [`DifferentiationInterface.twoarg_support`](@ref) on `SuperDiffBackend`.
+You also have to define [`ADTypes.mode`](@extref) and [`DifferentiationInterface.inplace_support`](@ref) on `SuperDiffBackend`.
 
 !!! info
     In the end, this backend struct will need to be contributed to [ADTypes.jl](https://github.com/SciML/ADTypes.jl).
@@ -79,5 +78,4 @@ GROUP = get(ENV, "JULIA_DI_TEST_GROUP", "Back/SuperDiff")
 
 but don't forget to switch it back before pushing.
 
-Finally, you need to add your backend to the documentation, modifying every page that involves a list of backends.
-That includes the README.
+Finally, you need to add your backend to the documentation, modifying every page that involves a list of backends (including the `README.md`).

DifferentiationInterface/docs/src/implementations.md

@@ -1,10 +1,6 @@
 # Implementations
 
-DifferentiationInterface.jl provides a handful of [operators](@ref "Operators") like [`gradient`](@ref) or [`jacobian`](@ref), each with several variants:
-
-- **out-of-place** or **in-place** behavior
-- **with** or **without primal** output value
-- support for **one-argument functions** `y = f(x)` or **two-argument functions** `f!(y, x)`
+DifferentiationInterface.jl provides a handful of [operators](@ref "Operators") like [`gradient`](@ref) or [`jacobian`](@ref), each with several variants: out-of-place or in-place behavior, with or without primal output value.
 
 While it is possible to define every operator using just [`pushforward`](@ref) and [`pullback`](@ref), some backends have more efficient implementations of high-level operators.
 When they are available, we nearly always call these backend-specific overloads.
@@ -24,7 +20,7 @@ The cells can have three values:
 ```@setup overloads
 using ADTypes: AbstractADType
 using DifferentiationInterface
-using DifferentiationInterface: twoarg_support, TwoArgSupported
+using DifferentiationInterface: inplace_support, InPlaceSupported
 using Markdown: Markdown
 
 using Diffractor: Diffractor
@@ -152,16 +148,16 @@ function print_overloads(backend, ext::Symbol)
     io = IOBuffer()
     ext = Base.get_extension(DifferentiationInterface, ext)
 
-    println(io, "#### One-argument functions `y = f(x)`")
+    println(io, "#### Out-of-place functions `f(x) = y`")
     println(io)
     print_overload_table(io, operators_and_types_f(backend), ext)
 
-    println(io, "#### Two-argument functions `f!(y, x)`")
+    println(io, "#### In-place functions `f!(y, x) = nothing`")
     println(io)
-    if twoarg_support(backend) == TwoArgSupported()
+    if inplace_support(backend) == InPlaceSupported()
         print_overload_table(io, operators_and_types_f!(backend), ext)
     else
-        println(io, "Backend doesn't support mutating functions.")
+        println(io, "Backend doesn't support in-place functions.")
     end
 
     return Markdown.parse(String(take!(io)))