Add support for diff of ref return types in rev mode

.github/workflows/ci.yml

@@ -38,11 +38,13 @@ jobs:
           chmod +x git-clang-format
       - name: Run git-clang-format
         run: |
+          PR_BASE=$(git rev-list ${{ github.event.pull_request.head.sha }} ^${{ github.event.pull_request.base.sha }} | tail --lines 1 | xargs -I {} git rev-parse {}~1)
+          echo "running git clang-format against $PR_BASE commit"
           git \
           -c color.ui=always \
           -c diff.wsErrorHighlight=all \
           -c color.diff.whitespace='red reverse' \
-          clang-format-15 --diff --binary clang-format-15 origin/master -- demos/ include/ lib/ tools/ || \
+          clang-format-15 --diff --binary clang-format-15 --commit $PR_BASE -- demos/ include/ lib/ tools/ || \
           (echo "Please run the following git-clang-format locally to fix the formatting: \n
                 git clang-format origin/master -- demos/ include/ lib/ tools/" && exit 1)
   build:
@@ -82,12 +84,12 @@ jobs:
             os: macos-latest
             compiler: clang
             clang-runtime: '14'
-            
+
           - name: osx-clang-runtime15
             os: macos-latest
             compiler: clang
             clang-runtime: '15'
-            
+
           - name: osx-clang-runtime16
             os: macos-latest
             compiler: clang
@@ -414,7 +416,7 @@ jobs:
             os: ubuntu-22.04
             compiler: clang-15
             clang-runtime: '14'
-          
+
           - name: ubu22-clang15-runtime15
             os: ubuntu-22.04
             compiler: clang-15
@@ -614,15 +616,15 @@ jobs:
         echo "PATH_TO_LLVM_BUILD=$env:PATH_TO_LLVM_BUILD" >> $env:GITHUB_ENV
     - name: Setup CUDA 8 on Linux
       if: ${{ matrix.cuda == true }}
-      run: |     
-        wget --no-verbose https://developer.nvidia.com/compute/cuda/8.0/Prod2/local_installers/cuda_8.0.61_375.26_linux-run 
+      run: |
+        wget --no-verbose https://developer.nvidia.com/compute/cuda/8.0/Prod2/local_installers/cuda_8.0.61_375.26_linux-run
         wget --no-verbose https://developer.nvidia.com/compute/cuda/8.0/Prod2/patches/2/cuda_8.0.61.2_linux-run
         sh ./cuda_8.0.61_375.26_linux-run --tar mxvf
         sudo cp InstallUtils.pm /usr/lib/x86_64-linux-gnu/perl-base
         export $PERL5LIB
-        sudo sh cuda_8.0.61_375.26_linux-run --override --no-opengl-lib --silent --toolkit --kernel-source-path=/lib/modules/4.15.0-1113-azure/build 
-        sudo sh cuda_8.0.61.2_linux-run --silent --accept-eula 
-        export PATH=/usr/local/cuda-8.0/bin:${PATH} 
+        sudo sh cuda_8.0.61_375.26_linux-run --override --no-opengl-lib --silent --toolkit --kernel-source-path=/lib/modules/4.15.0-1113-azure/build
+        sudo sh cuda_8.0.61.2_linux-run --silent --accept-eula
+        export PATH=/usr/local/cuda-8.0/bin:${PATH}
         export LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/usr/local/cuda-8.0/lib64
         echo "LD_LIBRARY_PATH=$LD_LIBRARY_PATH" >> $GITHUB_ENV
         echo "PATH=$PATH" >> $GITHUB_ENV

VERSION

@@ -1 +1 @@
-1.2~dev
+1.3~dev

docs/internalDocs/ReleaseNotes.md

@@ -2,7 +2,7 @@ Introduction
 ============
 
 This document contains the release notes for the automatic differentiation
-plugin for clang Clad, release 1.2. Clad is built on top of
+plugin for clang Clad, release 1.3. Clad is built on top of
 [Clang](http://clang.llvm.org) and [LLVM](http://llvm.org>) compiler
 infrastructure. Here we describe the status of Clad in some detail, including
 major improvements from the previous release and new feature work.
@@ -11,7 +11,7 @@ Note that if you are reading this file from a git checkout,
 this document applies to the *next* release, not the current one.
 
 
-What's New in Clad 1.2?
+What's New in Clad 1.3?
 ========================
 
 Some of the major new features and improvements to Clad are listed here. Generic
@@ -21,7 +21,7 @@ described first.
 External Dependencies
 ---------------------
 
-* Clad now works with clang-5.0 to clang-15
+* Clad now works with clang-5.0 to clang-16
 
 
 Forward Mode & Reverse Mode
@@ -54,7 +54,7 @@ Fixed Bugs
 [XXX](https://github.com/vgvassilev/clad/issues/XXX)
 
  <!---Get release bugs
- git log v1.0..master | grep 'Fixes|Closes'
+ git log v1.2..master | grep 'Fixes|Closes'
  --->
 
 Special Kudos
@@ -68,6 +68,6 @@ FirstName LastName (#commits)
 A B (N)
 
 <!---Find contributor list for this release
- git log --pretty=format:"%an"  v1.1...master | sort | uniq -c | sort -rn |\
+ git log --pretty=format:"%an"  v1.2...master | sort | uniq -c | sort -rn |\
    sed -E 's,^ *([0-9]+) (.*)$,\2 \(\1\),'
 --->

docs/userDocs/source/user/UsingVectorMode.rst

@@ -1,6 +1,10 @@
 Using Vector Mode for Differentiation
 **************************************
 
+.. note::
+    This feature is still under development and may result in unexpected
+    behavior. Please report any issues you find.
+
 For forward mode AD, the restriction is that the function can be only be
 differentiated with respect to a single input variable. However, in many cases,
 it is desirable to differentiate a function with respect to multiple input

environment.yml

@@ -1,5 +1,5 @@
 channels:
   - conda-forge
 dependencies:
-  - clad=1.0
+  - clad=0.9
   - xeus-cling

include/clad/Differentiator/DerivativeBuilder.h

@@ -77,7 +77,7 @@ namespace clad {
     friend class ReverseModeVisitor;
     friend class HessianModeVisitor;
     friend class JacobianModeVisitor;
-
+    friend class ReverseModeForwPassVisitor;
     clang::Sema& m_Sema;
     plugin::CladPlugin& m_CladPlugin;
     clang::ASTContext& m_Context;

include/clad/Differentiator/DiffMode.h

@@ -11,6 +11,7 @@ enum class DiffMode {
   reverse,
   hessian,
   jacobian,
+  reverse_mode_forward_pass,
   error_estimation
 };
 }

include/clad/Differentiator/Differentiator.h

@@ -20,6 +20,12 @@
 #include <cstring>
 
 namespace clad {
+  template<typename T, typename U>
+  struct ValueAndAdjoint {
+    T value;
+    U adjoint;
+  };
+
   /// \returns the size of a c-style string
   CUDA_HOST_DEVICE unsigned int GetLength(const char* code) {
     unsigned int count;

include/clad/Differentiator/ReverseModeForwPassVisitor.h

@@ -0,0 +1,38 @@
+#ifndef CLAD_TRANSFORM_SOURCE_FN_VISITOR_H
+#define CLAD_TRANSFORM_SOURCE_FN_VISITOR_H
+
+#include "clad/Differentiator/ParseDiffArgsTypes.h"
+#include "clad/Differentiator/ReverseModeVisitor.h"
+
+#include "clang/AST/StmtVisitor.h"
+#include "clang/Sema/Sema.h"
+
+#include "llvm/ADT/SmallVector.h"
+
+namespace clad {
+class ReverseModeForwPassVisitor : public ReverseModeVisitor {
+private:
+  Stmts m_Globals;
+
+  llvm::SmallVector<clang::QualType, 8>
+  ComputeParamTypes(const DiffParams& diffParams);
+  clang::QualType ComputeReturnType();
+  llvm::SmallVector<clang::ParmVarDecl*, 8> BuildParams(DiffParams& diffParams);
+  clang::QualType GetParameterDerivativeType(clang::QualType yType,
+                                             clang::QualType xType);
+
+public:
+  ReverseModeForwPassVisitor(DerivativeBuilder& builder);
+  DerivativeAndOverload Derive(const clang::FunctionDecl* FD,
+                                   const DiffRequest& request);
+
+  StmtDiff ProcessSingleStmt(const clang::Stmt* S);
+
+  StmtDiff VisitStmt(const clang::Stmt* S) override;
+  StmtDiff VisitCompoundStmt(const clang::CompoundStmt* CS) override;
+  StmtDiff VisitDeclRefExpr(const clang::DeclRefExpr* DRE) override;
+  StmtDiff VisitReturnStmt(const clang::ReturnStmt* RS) override;
+};
+} // namespace clad
+
+#endif

include/clad/Differentiator/ReverseModeVisitor.h

@@ -31,7 +31,7 @@ namespace clad {
       : public clang::ConstStmtVisitor<ReverseModeVisitor, StmtDiff>,
         public VisitorBase {
 
-  private:
+  protected:
     // FIXME: We should remove friend-dependency of the plugin classes here.
     // For this we will need to separate out AST related functions in
     // a separate namespace, as well as add getters/setters function of
@@ -321,11 +321,11 @@ namespace clad {
     StmtDiff VisitArraySubscriptExpr(const clang::ArraySubscriptExpr* ASE);
     StmtDiff VisitBinaryOperator(const clang::BinaryOperator* BinOp);
     StmtDiff VisitCallExpr(const clang::CallExpr* CE);
-    StmtDiff VisitCompoundStmt(const clang::CompoundStmt* CS);
+    virtual StmtDiff VisitCompoundStmt(const clang::CompoundStmt* CS);
     StmtDiff VisitConditionalOperator(const clang::ConditionalOperator* CO);
     StmtDiff VisitCXXBoolLiteralExpr(const clang::CXXBoolLiteralExpr* BL);
     StmtDiff VisitCXXDefaultArgExpr(const clang::CXXDefaultArgExpr* DE);
-    StmtDiff VisitDeclRefExpr(const clang::DeclRefExpr* DRE);
+    virtual StmtDiff VisitDeclRefExpr(const clang::DeclRefExpr* DRE);
     StmtDiff VisitDeclStmt(const clang::DeclStmt* DS);
     StmtDiff VisitFloatingLiteral(const clang::FloatingLiteral* FL);
     StmtDiff VisitForStmt(const clang::ForStmt* FS);
@@ -335,8 +335,8 @@ namespace clad {
     StmtDiff VisitIntegerLiteral(const clang::IntegerLiteral* IL);
     StmtDiff VisitMemberExpr(const clang::MemberExpr* ME);
     StmtDiff VisitParenExpr(const clang::ParenExpr* PE);
-    StmtDiff VisitReturnStmt(const clang::ReturnStmt* RS);
-    StmtDiff VisitStmt(const clang::Stmt* S);
+    virtual StmtDiff VisitReturnStmt(const clang::ReturnStmt* RS);
+    virtual StmtDiff VisitStmt(const clang::Stmt* S);
     StmtDiff VisitUnaryOperator(const clang::UnaryOperator* UnOp);
     StmtDiff VisitExprWithCleanups(const clang::ExprWithCleanups* EWC);
     /// Decl is not Stmt, so it cannot be visited directly.

lib/Differentiator/CMakeLists.txt

@@ -31,6 +31,7 @@ add_llvm_library(cladDifferentiator
   HessianModeVisitor.cpp
   JacobianModeVisitor.cpp
   MultiplexExternalRMVSource.cpp
+  ReverseModeForwPassVisitor.cpp
   ReverseModeVisitor.cpp
   StmtClone.cpp
   VectorForwardModeVisitor.cpp

lib/Differentiator/DerivativeBuilder.cpp

@@ -22,6 +22,8 @@
 #include "clad/Differentiator/HessianModeVisitor.h"
 #include "clad/Differentiator/JacobianModeVisitor.h"
 #include "clad/Differentiator/ReverseModeVisitor.h"
+#include "clad/Differentiator/ReverseModeForwPassVisitor.h"
+#include "clad/Differentiator/DiffPlanner.h"
 #include "clad/Differentiator/StmtClone.h"
 #include "clad/Differentiator/VectorForwardModeVisitor.h"
 
@@ -230,6 +232,9 @@ namespace clad {
       result = V.DerivePullback(FD, request);
       if (!m_ErrorEstHandler.empty())
         CleanupErrorEstimation(m_ErrorEstHandler, m_EstModel);
+    } else if (request.Mode == DiffMode::reverse_mode_forward_pass) {
+      ReverseModeForwPassVisitor V(*this);
+      result = V.Derive(FD, request);
     } else if (request.Mode == DiffMode::hessian) {
       HessianModeVisitor H(*this);
       result = H.Derive(FD, request);