From 1093218d6f0e114eb9fa52d60ca525bf9dd9f98a Mon Sep 17 00:00:00 2001
From: Sai Praveen Bangaru <31557731+saipraveenb25@users.noreply.github.com>
Date: Thu, 20 Oct 2022 14:22:00 -0400
Subject: Modified the new type system to support generic differentiable types
 … (#2413)
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* Modified the new type system to support generic differentiable types and added support for differentiating overloaded functions.

* Changed a few asserts to release asserts to avoid unreferenced variable errors

* Fixed a naming issue with TypeWitnessBreadcumb::Flavor::Decl

* Added logic to avoid tracking differentiable types if the module does not use auto-diff or define differentiable types.

* Moved the auto-diff passes to after the specialization step, added a more complex generics test

* Added a generics stress test and fixed AST-side logic. IR side needs some more work

* Added differential getter and setter logic, fixed multiple issues with DifferentiableTypeDictionary, added support for loops and conditions

* Changed differential getters to use pointer types, added getter type checking

* Fixed some bugs related to diff type registration and differential getters

* Removed some superfluous code

* Removed some more unused code.

* Fixed an issue with witness substitution

* Minor fix

Co-authored-by: Yong He <yonghe@outlook.com>
---
 source/slang/diff.meta.slang | 133 ++++++++++++++++++++++++++++++++++---------
 1 file changed, 106 insertions(+), 27 deletions(-)

(limited to 'source/slang/diff.meta.slang')

diff --git a/source/slang/diff.meta.slang b/source/slang/diff.meta.slang
index e604140ae..26fec224c 100644
--- a/source/slang/diff.meta.slang
+++ b/source/slang/diff.meta.slang
@@ -8,18 +8,118 @@ syntax __differentiate_jvp : JVPDerivativeModifier;
 __attributeTarget(FuncDecl)
 attribute_syntax [__custom_jvp(function)]   : CustomJVPAttribute;
 
-//@ public:
-
-    /// Interface to denote types as differentiable.
-    /// Allows for user-specified differential types as
-    /// well as automatic generation, for when the associated type
-    /// hasn't been declared explicitly.
+/// Interface to denote types as differentiable.
+/// Allows for user-specified differential types as
+/// well as automatic generation, for when the associated type
+/// hasn't been declared explicitly.
+/// Note that the requirements must currently be defined in this exact order
+/// since the auto-diff pass relies on the order to grab the struct keys.
+/// 
 __magic_type(DifferentiableType)
 interface IDifferentiable
 {
     associatedtype Differential;
+    
+    static Differential zero();
+
+    static Differential dadd(Differential, Differential);
+
+    static Differential dmul(This, Differential);
 };
 
+// Add extensions for the standard types
+extension float : IDifferentiable
+{
+    typedef float Differential;
+    
+    [__unsafeForceInlineEarly]
+    static Differential zero()
+    {
+        return 0.f;
+    }
+
+    [__unsafeForceInlineEarly]
+    static Differential dadd(Differential a, Differential b)
+    {
+        return a + b;
+    }
+
+    [__unsafeForceInlineEarly]
+    static Differential dmul(This a, Differential b)
+    {
+        return a * b;
+    }
+}
+
+extension vector<float, 3> : IDifferentiable
+{
+    typedef vector<float, 3> Differential;
+
+    [__unsafeForceInlineEarly]
+    static Differential zero()
+    {
+        return vector<float, 3>(0.f);
+    }
+
+    [__unsafeForceInlineEarly]
+    static Differential dadd(Differential a, Differential b)
+    {
+        return a + b;
+    }
+
+    [__unsafeForceInlineEarly]
+    static Differential dmul(This a, Differential b)
+    {
+        return a * b;
+    }
+}
+
+extension vector<float, 2> : IDifferentiable
+{
+    typedef vector<float, 2> Differential;
+
+    [__unsafeForceInlineEarly]
+    static Differential zero()
+    {
+        return vector<float, 2>(0.f);
+    }
+
+    [__unsafeForceInlineEarly]
+    static Differential dadd(Differential a, Differential b)
+    {
+        return a + b;
+    }
+
+    [__unsafeForceInlineEarly]
+    static Differential dmul(This a, Differential b)
+    {
+        return a * b;
+    }
+}
+
+extension vector<float, 4> : IDifferentiable
+{
+    typedef vector<float, 4> Differential;
+
+    [__unsafeForceInlineEarly]
+    static Differential zero()
+    {
+        return vector<float, 4>(0.f);
+    }
+
+    [__unsafeForceInlineEarly]
+    static Differential dadd(Differential a, Differential b)
+    {
+        return a + b;
+    }
+
+    [__unsafeForceInlineEarly]
+    static Differential dmul(This a, Differential b)
+    {
+        return a * b;
+    }
+}
+
     /// Pair type that serves to wrap the primal and
     /// differential types of an arbitrary type T.
 __generic<T : IDifferentiable>
@@ -47,24 +147,3 @@ struct __DifferentialPair
         return p();
     }
 };
-
-// Add extensions for the standard types
-extension float : IDifferentiable
-{
-    typedef float Differential;
-}
-
-extension vector<float, 3> : IDifferentiable
-{
-    typedef vector<float, 3> Differential;
-}
-
-extension vector<float, 2> : IDifferentiable
-{
-    typedef vector<float, 2> Differential;
-}
-
-extension vector<float, 4> : IDifferentiable
-{
-    typedef vector<float, 4> Differential;
-}
-- 
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