refactor: Remove autodiff (acts-project#2793)

related issues (closes acts-project#2792)
- acts-project#2792

`autodiff` became more of a burden at some point. Since we do not consistently template all the quantities we might want to derive later this became more of an exception. I propose to remove it for now until we have a broader solution or purpose for it

.gitlab-ci.yml

@@ -407,7 +407,6 @@ linux_ubuntu_2204_clang:
       -DACTS_BUILD_PLUGIN_JSON=ON
       -DACTS_BUILD_FATRAS=ON
       -DACTS_BUILD_PLUGIN_LEGACY=ON
-      -DACTS_BUILD_PLUGIN_AUTODIFF=OFF
       -DACTS_BUILD_EXAMPLES_DD4HEP=OFF
       -DACTS_BUILD_PLUGIN_EDM4HEP=OFF
       -DACTS_BUILD_EXAMPLES_GEANT4=ON

CMakeLists.txt

@@ -29,8 +29,6 @@ option(ACTS_FORCE_ASSERTIONS "Force assertions regardless of build type" OFF)
 # external library options
 option(ACTS_USE_SYSTEM_LIBS "Use system libraries by default" OFF)
 # plugins related options
-option(ACTS_BUILD_PLUGIN_AUTODIFF "Build the autodiff plugin" OFF)
-option(ACTS_USE_SYSTEM_AUTODIFF "Use autodiff provided by the system instead of the bundled version" ${ACTS_USE_SYSTEM_LIBS})
 option(ACTS_USE_SYSTEM_ACTSVG "Use the ActSVG system library" ${ACTS_USE_SYSTEM_LIBS})
 option(ACTS_BUILD_PLUGIN_ACTSVG "Build SVG display plugin" OFF)
 option(ACTS_BUILD_PLUGIN_CUDA "Build CUDA plugin" OFF)
@@ -147,7 +145,6 @@ set_option_if(
   ACTS_BUILD_FATRAS
   ACTS_BUILD_EXAMPLES OR ACTS_BUILD_EVERYTHING)
 set_option_if(ACTS_BUILD_PLUGIN_LEGACY ACTS_BUILD_EVERYTHING)
-set_option_if(ACTS_BUILD_PLUGIN_AUTODIFF ACTS_BUILD_EVERYTHING)
 set_option_if(ACTS_BUILD_PLUGIN_EXATRKX ACTS_BUILD_EXAMPLES_EXATRKX)
 set_option_if(ACTS_BUILD_PLUGIN_FPEMON 
   ACTS_BUILD_EXAMPLES OR ACTS_BUILD_EVERYTHING)
@@ -283,14 +280,6 @@ if(ACTS_BUILD_PLUGIN_ACTSVG)
     add_subdirectory(thirdparty/actsvg)
   endif()
 endif()
-if(ACTS_BUILD_PLUGIN_AUTODIFF)
-  if(ACTS_USE_SYSTEM_AUTODIFF)
-    find_package(autodiff ${_acts_autodiff_version} CONFIG REQUIRED)
-    message(STATUS "Using system installation of autodiff")
-  else()
-    add_subdirectory(thirdparty/autodiff)
-  endif()
-endif()
 if(ACTS_BUILD_PLUGIN_CUDA)
   enable_cuda()
 endif()

Core/include/Acts/EventData/Charge.hpp

@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include "Acts/Definitions/Algebra.hpp"
 #include "Acts/Definitions/Units.hpp"
 #include "Acts/EventData/ChargeConcept.hpp"
 #include "Acts/Utilities/Concepts.hpp"
@@ -67,19 +68,17 @@ struct Neutral {
 
   constexpr float absQ() const noexcept { return 0; }
 
-  template <typename T>
-  constexpr auto extractCharge(T /*qOverP*/) const noexcept {
+  constexpr float extractCharge(ActsScalar /*qOverP*/) const noexcept {
     return 0.0f;
   }
 
-  template <typename T>
-  constexpr auto extractMomentum(T qOverP) const noexcept {
+  constexpr ActsScalar extractMomentum(ActsScalar qOverP) const noexcept {
     assert(qOverP >= 0 && "qOverP cannot be negative");
     return 1.0f / qOverP;
   }
 
-  template <typename P, typename Q>
-  constexpr auto qOverP(P momentum, Q signedQ) const noexcept {
+  constexpr ActsScalar qOverP(ActsScalar momentum,
+                              float signedQ) const noexcept {
     assert((signedQ != 0) && "charge must be 0");
     (void)signedQ;
     return 1.0f / momentum;
@@ -112,24 +111,18 @@ struct SinglyCharged {
 
   constexpr float absQ() const noexcept { return UnitConstants::e; }
 
-  template <typename T>
-  constexpr auto extractCharge(T qOverP) const noexcept {
-    // using because of autodiff
-    using std::copysign;
-    return copysign(UnitConstants::e, qOverP);
+  constexpr float extractCharge(ActsScalar qOverP) const noexcept {
+    return std::copysign(UnitConstants::e, qOverP);
   }
 
-  template <typename T>
-  constexpr auto extractMomentum(T qOverP) const noexcept {
-    // using because of autodiff
-    using std::abs;
+  constexpr ActsScalar extractMomentum(ActsScalar qOverP) const noexcept {
     return extractCharge(qOverP) / qOverP;
   }
 
-  template <typename P, typename Q>
-  constexpr auto qOverP(P momentum, Q signedQ) const noexcept {
-    using std::abs;
-    assert((abs(signedQ) == UnitConstants::e) && "absolute charge must be e");
+  constexpr ActsScalar qOverP(ActsScalar momentum,
+                              float signedQ) const noexcept {
+    assert((std::abs(signedQ) == UnitConstants::e) &&
+           "absolute charge must be e");
     return signedQ / momentum;
   }
 
@@ -158,24 +151,16 @@ class NonNeutralCharge {
 
   constexpr float absQ() const noexcept { return m_absQ; }
 
-  template <typename T>
-  constexpr auto extractCharge(T qOverP) const noexcept {
-    // using because of autodiff
-    using std::copysign;
-    return copysign(m_absQ, qOverP);
+  constexpr float extractCharge(ActsScalar qOverP) const noexcept {
+    return std::copysign(m_absQ, qOverP);
   }
-  template <typename T>
-  constexpr auto extractMomentum(T qOverP) const noexcept {
-    // using because of autodiff
-    using std::abs;
+  constexpr ActsScalar extractMomentum(ActsScalar qOverP) const noexcept {
     return extractCharge(qOverP) / qOverP;
   }
 
-  template <typename P, typename Q>
-  constexpr auto qOverP(P momentum, Q signedQ) const noexcept {
-    // using because of autodiff
-    using std::abs;
-    assert(abs(signedQ) == m_absQ && "inconsistent charge");
+  constexpr ActsScalar qOverP(ActsScalar momentum,
+                              float signedQ) const noexcept {
+    assert(std::abs(signedQ) == m_absQ && "inconsistent charge");
     return signedQ / momentum;
   }
 
@@ -208,24 +193,16 @@ class AnyCharge {
 
   constexpr float absQ() const noexcept { return m_absQ; }
 
-  template <typename T>
-  constexpr auto extractCharge(T qOverP) const noexcept {
-    // using because of autodiff
-    using std::copysign;
-    return copysign(m_absQ, qOverP);
+  constexpr float extractCharge(ActsScalar qOverP) const noexcept {
+    return std::copysign(m_absQ, qOverP);
   }
-  template <typename T>
-  constexpr auto extractMomentum(T qOverP) const noexcept {
-    // using because of autodiff
-    using std::abs;
+  constexpr ActsScalar extractMomentum(ActsScalar qOverP) const noexcept {
     return (m_absQ != 0.0f) ? extractCharge(qOverP) / qOverP : 1.0f / qOverP;
   }
 
-  template <typename P, typename Q>
-  constexpr auto qOverP(P momentum, Q signedQ) const noexcept {
-    // using because of autodiff
-    using std::abs;
-    assert(abs(signedQ) == m_absQ && "inconsistent charge");
+  constexpr ActsScalar qOverP(ActsScalar momentum,
+                              float signedQ) const noexcept {
+    assert(std::abs(signedQ) == m_absQ && "inconsistent charge");
     return (m_absQ != 0.0f) ? signedQ / momentum : 1.0f / momentum;
   }
 

Core/include/Acts/EventData/ChargeConcept.hpp

@@ -24,19 +24,14 @@ namespace Acts {
 template <typename C>
 concept ChargeConcept = requires(C c, float f, double d) {
   {C{f}};
-  { c.absQ() } -> std::same_as<float>;
-
-  { c.extractCharge(f) } -> std::convertible_to<float>;
-  { c.extractCharge(d) } -> std::convertible_to<float>;
-
-  { c.extractMomentum(f) } -> std::convertible_to<float>;
-  { c.extractMomentum(d) } -> std::convertible_to<float>;
-
-  { c.qOverP(f, f) } -> std::same_as<float>;
-  { c.qOverP(d, d) } -> std::same_as<double>;
 
   { c == c } -> std::same_as<bool>;
   { c != c } -> std::same_as<bool>;
+
+  { c.absQ() } -> std::same_as<float>;
+  { c.extractCharge(d) } -> std::same_as<float>;
+  { c.extractMomentum(d) } -> std::same_as<double>;
+  { c.qOverP(d, d) } -> std::same_as<double>;
 };
 
 }  // namespace Acts