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OpenVDB AX Version History

Version 1.0.0 - In Development

New Features:
- Introduced new error logging framework for AX syntax errors/warnings,
  allowing capture and reporting of syntax errors in AX code beyond the
  first error, as well as graceful breaking of the compilation process if it
  cannot continue. This allows for more useful error messages and other
  quality of life improvements such as printing of the offending lines of
  code.
- Synced AX library version to VDB version. The library version now matches
  the version of VDB it is built against. This is in preparation for porting
  into the OpenVDB repository.
- Added sign() to return -1, 0 or 1 depending on the sign of a scalar input

Improvements:
- Update various API methods and objects to use Logger including Compiler
  and ComputeGenerators
- Moved initialization methods to ax.cc
- Reworked all existing exception types with the majority being converted to
  logger errors. Remaining exception are consolidated library faults.
- Updated command line binary to use Logger and report more than one error
  message and print error locations.
- Added --werror and --max-errors options to the command line binary
- Fixed various warnings when building with GCC 9.3.1
- Added some missing int64_t function signatures

Compiler:
- Added new compile methods using Logger/deprecated old compile methods
  taking vectors of strings. Methods that don't take a logger collect all
  possible errors before throwing (on error).
- Added debug checks to ensure functions are registered correctly

AST:
- Moved parse methods from AST.h to new Parse.h
- Added new parse method returning const AST for use with line/col tracking
  in codegen by Logger

Houdini:
- Move OpenVDB AX SOP into VDB/ASWF folder
- Updated to use new Logger, can now report more than one error message at a
  time.

CMake / Build / Testing:
- Increased the minimum CMake version requirement to 3.12
- Increased the minimum LLVM version requirement to 6.0.0
- Switch to use GNU Install Dirs
- Fixed github actions not running on branches with slashes
- Removed deprecated openvdb_ax_houdini CMake var
- Updated to use relative includes
- Added Logger to collect and report errors and warnings
- Switched to CMake doxygen support and removed doxygen-config
- Switched to vfxall clang docker containers for github actions and added a
  vfx 2021 platform test
- Removed LLVM 6 macos test as it's been removed from brew
- Changed the way in which the AX grammar is included through CMake depending
  on if it is being rebuilt
- Flipped the compile time matrix support check. Changed the MATRIX_SUPPORT
  CMake variable to OPENVDB_HAS_MATRIX_SUPPORT. If not defined, implies
  OpenVDB does not have matrix grid support

Version 0.3.0 - August 20, 2020

New Features:
- New and improved doxygen and language reference material. NOTE: Work on
  this is still in progress. Incremental changes will continue to be made
  up to a 1.0.0 release.
- Added ternary conditional operator 'a ? b : c' (and "Elvis" operator
  'a ?: c') support
- Added full AX type support for matching VDB Point/Volume types which may
  or may not be registered. Registration of these types still depends on
  on downstream software.
- Introduced a single header which exposes new ax::run() pipeline methods.
  These provide easier access to running a full ax pipeline
- The AX VolumeExecutable can now optionally run over any active tile level
  of an OpenVDB Tree.

Improvements:
- Updated scalar to matrix promotion rules. When a scalar is promoted to a
  matrix (either through direct/indirect assignments, binary or ternary
  operators) it now produces the diagonal matrix with an equivalent
  dimension with components equal to the scalar. For example "mat3d@a = 2.0;"
  produces { 2.0,0.0,0.0  0.0,2.0,0.0  0.0,0.0,2.0 }
- polardecompose() no longer throws on unsuccessful inversion and will now
  return false if it fails.
- Removed the ability to compare vectors or matrices with the following
  relation operators: <= >= < >
- Removed support for implicit narrowing of vector/matrices to scalars
  i.e. vec3f a; int b = a;
- Removed support for incrementing or decrementing boolean values.
- Added support for unary logical/bitwise not on integer vector types
  e.g. vec3i a; a = !a;
- Implemented complete support for the comma operator e.g. int a = (1,2,3);
  which evaluates all expressions in order, returning the last expression's
  value.
- Compound assignments no longer evaluate the left hand side twice.
- Added the ability to assign to precremented values i.e. ++a = 1;
- Added API support for VDB 7.1.0.

Bug Fixes:
- Fixed a bug which would cause a crash if a vector/matrix was accessed
  with a single index consisting of an invalid type. e.g. mat[{1,1,1}];
- Fixed parser issues related to parenthesized comma operators. This
  primarily caused a parser failure when calling a function with a
  parenthesized expression e.g. print((1,2));
- Fixed some attribute dependency detections that would miss dependencies
  in conditions of loops.
- Fixed a variety of boolean conversion logic in binary, unary, crement
  and direct/indirect assignments. Boolean conversion from scalars now
  adheres to C/C++ standard.
- Fixed a potential bug which could cause a crash if the target machine type
  could not be inferred by LLVM.
- Fixed a small memory leak which would occur when invalid code was parsed
- Fixed issues with the way declaration lists were being printed with
  ast::reprint in loop initializers
- Fixed a potential crash when calling incompatible VDB functions for points
  or volumes

Houdini:
- The AX SOP automatically drops unsupported grid types with a warning.
- Improved the performance of the chramp() method. Evaluation is now 2x
  faster and supports all Houdini ramp parameter interpolation modes.

Compiler:
- Removed unnecessary parser callback members from the Compiler
- Reverse the LLVM context and engine constructor order on the executables

Executables:
- Added a single openvdb::GridBase execute method to the VolumeExecutable
- Reworked the executables execute signatures. These now only accept the
  grids to execute. All other parameters can be set via new setters/getters
  on the executable class interface.
- Added an explicit copy constructor to both executables which shallow
  copies all LLVM constructors but deep copies the executable settings.
- Exposed the tree value level iterator on the VolumeExecutable to allow
  OpenVDB node level selection
- Exposed the threading grain size options on both executables
- Removed the public constructors from the executables. These should only be
  created by the Compiler.
- Improved both Volume and Point executable internal compute function
  bindings

Compiler:
- Removed unnecessary parser callback members from the Compiler
- Reverse the LLVM context and engine constructor order on the executables

Executables:
- Added a single openvdb::GridBase execute method to the VolumeExecutable
- Reworked the executables execute signatures. These now only accept the
  grids to execute. All other parameters can be set via new setters/getters
  on the executable class interface.
- Added an explicit copy constructor to both executables which shallow
  copies all LLVM constructors but deep copies the executable settings.
- Exposed the tree value level iterator on the VolumeExecutable to allow
  OpenVDB node level selection
- Exposed the threading grain size options on both executables
- Removed the public constructors from the executables. These should only be
  created by the Compiler.
- Improved both Volume and Point executable internal compute function
  bindings

AST:
- New AST Nodes for Comma and Ternary operators and corresponding visitor
  patterns.
- Removed the ExpressionList AST node which didn't represent a
  syntactical structure within AX. Such expressions are now either
  arguments or Comma operators
- Renamed the then and else branch methods on the CondtionalStatement AST
  node to true and false respectively. This matches the new Ternary AST
  node.
- Reordered the Binary and Unary Operator AST node constructors to always
  take the AST node operands first. This better matches other AST nodes.
- Restructured the Assign AST node to better handle compound assignments.
  The node no longer necessarily stores a binary expression on the right
  hand side to represent the compound assignment and instead takes an
  optional binary token.
- Swapped the right and left order of operands on the Assign AST node
  to better match other AST nodes. This also changes default traversal
  order.
- FunctionCall, ArrayUnpack and ArrayPack AST nodes no longer store
  ExpressionList nodes and instead directly store the AST nodes
  representing their arguments.
- Restructured Declaration AST nodes. These are no longer derived
  variables and are instead Statements with Local AST composition.
  Optional initializer expressions can also be stored on declarations
  instead of the previous nesting within AssignExpressions.
- Improved the result of ast::reprint in regards to scoped blocks
  consistency.
- Removed the ast::variableDependencies method from the public API.

Grammar:
- Changes to array packs where arguments are stored in a temporary vector
  of nodes until the parsing context can be inferred. This avoid conflicts
  with scopes.
- Split function call grammar into two rules which append arguments.
- Changes to declarations to support their new context as statements.
- Changes to assign expressions such that compound expressions directly
  store the right hand side instead of building additional binary
  expressions.
- Constructor changes in binary and unary grammar rules to match AST.
- New ternary grammar rules. Support for ? and : tokens in the lexer.
- Added destructor directives to handle cleanup of bad symbols.

Code Generation:
- Converted static methods on the ArgumentIterator class to a generic
  apply method
- Support for Comma and Ternary Operator code generation.
- Split out the assignment and binary logic into protected methods. Declare
  visits use the assignment logic, compound assignments use the binary
  logic.

CMake / Build / Testing:
- Synced CMake modules from OpenVDB repository
- Added github actions CI for VFX platforms 2019 and 2020 which match
  existing travis functionality.
- Added whitespace github action tests
- Added doxygen code block github action tests
- Bison now errors on any warnings during grammar generation.
- Updated CMake use of llvm_map_components_to_libnames to support LLVM 10
  and added LLVM 10 CI.
- Added matrix grid detection during the CMake build step.
- Fixed TestLoopNode tests which were not being executed
- Started re-factor of auto-generated integration tests and considerably
  improved test coverage. AX tests can be regenerated with the -g argument
  to the unit test binary.
- Removed travis CI in favour of github actions

Version 0.2.0 - March 5, 2020

As of this release, a C++14 compiler is required.

New Features:
- AX now generates all target machine (host) optimizations by default. This
  includes any supported SIMD (sse, avx etc.) instructions for SLP
  vectorization
- A full restructure of the developer Function framework with the switch to
  IR functions implementations over C bindings (where available). Up until
  now, natively supported functions in AX have used their C bindings by
  default. This release defaults to their IR implementations which, along
  with full vectorization support, allows for the full potential of all LLVM
  optimizations. This is most noticeable when using function inside of loops
  or in larger AX code snippets
- New functions added: acosh, asinh, atanh, diag
- New options and output to the vdb_ax binary. --try-compile provides a way
  to test if a given AX code snippet will compile for a particular VDB
  target. Verbose mode with -v now provides better formatted output with
  more detailed timing reports.
- Added the ability to provide external string data to AX which can be
  accessed with string$ (or chs() in Houdini)
- Added support for vec4 and string VDB volumes. Note that vec4 volumes are
  not registered by default

Improvements:
- Significant performance improvements to AX execution with the introduction of:
    - Proper SLP vectorization with supported host features
    - Defaulting IR functions to ON
    - Loop allocation fixes (see bug fixes)
    - Constant Folding for scalar C bindings
- Introduced initial constant folding for scalar C bindings. Functions which
  are called with known constants are evaluated at compile time. Note that
  CF for IR Functions is left to LLVM's optimization passes
- Added support for vec2 and vec4 arguments for length() and lengthsq()
- Added a new floating point signature for abs() (which calls fabs) to avoid
  implicit casting of integer arguments

Bug Fixes:
- Fixed a bug where assignments from functions which return void could cause
  a crash
- Fixed a bug where functions which modified reference arguments (such as
  transform, posttransform) would cast the modifiable argument, resulting in
  the result not being set. These functions will now error with invalid
  signatures and require the correct argument types to be provided
- Fixed an issue which could cause stack overflows when using scalar or
  array (vec/mat) allocations within loops
- Fixed an issue which could cause a crash when using uninitialized strings
  in compound expressions
- Fixed a bug where binary string concatenations could cause spurious
  characters to appear with print()
- Fixed a bug where vec4 types were being interpreted as vec3

Code Generation:
- Assignment and binary string operators now always copy the null terminator
- Added new IR function logic for lerp and for normalization of integer
  vectors
- The ast::FunctionCall visit now always pushes back the function result
- Strings are always initialized to the empty string
- All allocations, aside from string allocs, have been converted to function
  prologue static allocas
- New codegen/ConstantFolding.h which provides the generic framework for
  constant folding C bindings
- Renamed the FunctionBase class to FunctionGroup
- Renamed the FunctionSignatureBase class to Function and re-structured its
  member implementations
- New classes for derived Functions, CFunctionBase and IRFunctionBase, which
  can be further subclassed for the respective function type.
- A new interface class SRetFunction for functions which require structural
  returns
- New framework for building and creating a function. The FunctionBuilder
  provides a way to interface with the function types in FunctionTypes.h
  without having to manually subclass.
- Exposed the ability to customize llvm function attributes.
- Removed the unnecessary use of std::function on templated classes and
  methods
- Re-structured all native functions to use the new FunctionBuilder
- A variety of IR fixes to some native functions
- Re-structured all IR functions which required structural returns.
  Previously, these function would produce invalid results unless they were
  forcefully inlined. SRET IR methods now behave in the same way as SRET C
  bindings
- Improvements to the LLVMType trait structures. These have been mostly
  consolidated to take advantage of new LLVM methods
- Added a new AliasTypeMap trait structure in Types.h to allow for safer
  and restricted front-end to back-end type mapping
- New insertStaticAlloca utility method for creating function prologue
  static allocations. New isValidCast utility method to check if a cast is
  valid between two types
- Removed a number of unused utility methods
- Removed the function arguments vector from the ComputeGenerator in favor
  of new utility methods to extract arguments (extractArgument)
- Renamed the ComputeGenerator functions to prefix with ax and suffix
  with the generator type

Compiler:
- Initial implementation of LLVM's new PassManager. Currently disabled by
  default. This has not been fully configured to work with target machine
  optimizations.
- Introduced an internal compiler function, initializeTargetMachine, to
  create the target machine representing the available feature set of the
  host
- Renamed the mPrioritiseFunctionIR Function Option to mPrioritiseIR and
  defaulted it to ON
- Introduced a mConstantFoldCBindings Function Option which defaults to ON
- Added support for AXStringMetadata during global mapping for external
  values

Math:
- Exposed the curlnoise functions from StandardFunctions to the
  OpenSimplexNoise headers

CMake / Build / Testing:
- New test suites for various back-end utilities
- Added CMake SIMD options. Note that these optional apply to the compiled
  CXX source files of OpenVDB AX, not the JIT LLVM IR. The IR is always
  optimized to the host specification.
- Set the required LANGUAGES for OpenVDB AX projects to CXX
- Added significantly more function tests with profiling options
- BISON 3.0 is now marked as required if the grammar is to be regenerated
- New developer options, USE_NEW_PASS_MANAGER and OPENVDB_AX_TEST_PROFILE
- Travis fixes to build against VDB 6.2.1
- Removed the deprecated Makefiles

Version 0.1.1 - December 3, 2019

New Features:
- Added support for shl and ashr binary and assignment operations
  (<<, >>, <<=, >>=)
- New functions added: hash, lerp, polardecompose, trace
- rand() can now be called without a seed argument for improved performance.
  It must still be initialized with a seed at least once for deterministic
  results
- Exposed the ability to control whether new points attributes or VDB grids
  are automatically created when accessed if they do not exist

Improvements:
- Fixed some assertion errors/warnings when compiled with OPENVDB_CXX_STRICT
- Functions printed from the vdb_ax binary are now ordered alphabetically
- Simplified the logic in PointExecuterOp when a transform is required
- Improved the peak memory usage when reading from point positions

Houdini:
- New Evaluation Node Path parameter on the OpenVDB AX SOP to allow the SOP
  to be embedded into digital assets which expose the scripting interface
- Renamed the label from OpenVDB AX to VDB AX and moved the SOP to the VDB
  tab menu

CMake / Build / Testing:
- Updated all CMake Find modules to new standards from OpenVDB
- Improvements to cmake_minimum_required usage
- Improved the CMake branching for building against a Houdini installation
  when not building the OpenVDB AX SOP
- Moved codegen/OpenSimplexNoise.h to math/OpenSimplexNoise.h
- Updated unit test main to match current VDB with additional -shuffle option
- Replaced the CMake USE_SYSTEM_LIBRARY_PATHS option with
  DISABLE_CMAKE_SEARCH_PATHS and removed the hard coded list of
  SYSTEM_LIBRARY_PATHS in favor of using CMake's default search procedure.
  SYSTEM_LIBRARY_PATHS can still be used as a global list of paths for all
  dependency searches
- Disabled the python module by default

Version 0.1.0 - August 20, 2019

  Significant API and behaviour changes to OpenVDB AX in this release. Main
  API changes to codegen and AST components. Changes to OpenVDB Volume
  execution involving volumes of differing topologies. Active states now
  only determine the final application of a value rather than their impact on
  other volumes. For example:

    @a = 2;
    @b = @a;

  Irrespective of the overlapping activity, active @b voxels will be set to 2.
  Previously, this would only occur if @a was active at the given location,
  producing an implicit dependency of the active topology of @a on @b.

New Features:
- Support for for, while and do-while loops using standard c-like syntax.
  Includes break and continue keyword handling.
- Attribute, external and local support for 3x3 and 4x4 matrices and 2 and 4
  component vectors using the following tokens: mat3f, mat3d, mat4f, mat4d,
  vec2i, vec2f, vec2d, vec4i, vec4f, vec4d. Attributes and externals use the
  same tokens with @ and $ respectively
- New array style indexing support for vectors and matrices. Both can be
  indexed as an array using single [0] operations. Matrices can be indexed
  by row, column using [0,0]
- Added non keyword {} scope support
- New functions added: identity3, identity4, postscale, prescale,
  pretransform, simplexnoise, transform, transpose, curlsimplexnoise
- Significantly improved the performance of duplicate attribute accesses for
  points and volumes
- New compound assignment support for %=, &=, |= and ^=
- Better handling of LHS values within assignment operations, including
  support for cremented attributes
- Added pyopenvdbax module which exposes basic python bindings for AX.
  Provides compilation of executables and execution on VDB grids through
  Python.
- New arguments and modes to the vdb_ax binary. Analysis provides detailed
  information for a given ax snippet. More tools to search and list available
  functions
- Significantly re-worked volume execution. Each volume now receives the
  same singularly generated AX function. This more closely matches Houdini
  VEX behaviour
- New reprint() methods for printing an AST as AX code
- New scanner methods and API for returning detailed information from an AST
- Added the ability to iterate over any active state for Volumes

Bug fixes:
- Fixed a crash which could occur when destructing AX executables. This was
  due to the destruction order of LLVM objects which have since been
  reversed.
- Fixed a bug in SymbolTableBlocks::find which could occur if an out of range
  index was used
- Fixed an issue during AX compilation caused by invalid IR when branching
  after a return statement

Improvements:
- Function signatures are now printed with their AX types rather than their
  LLVM types (i.e. int(short) vs i32(i16))
- Significantly improved the descriptive printing of any parsed AST
- Added lexer location tracking for error line and column numbering
- Significantly improved backend string support
- Introduced new methods for dependency tracking attributes for efficiently
  determining the copy requirements of volumes
- Moved testing CMake config into its own CMakeLists.txt.
- Significantly improved the descriptive printing of any parsed AST
- Improved code documentation throughout the library
- Improved doxygen generation
- Improved position access for OpenVDB Points
- Renamed 'lookup' function to 'external'
- Moved function structs to .cc's and added methods to populate function
  registries
- Removed the old FunctionContext System from derived function methods
- Removed legacy code supporting multiple return values from
  FunctionSignatures
- Added virtual destructors to FunctionBase and FunctionSignature classes

Houdini:
- Fixed an issue where the VDB name was taken over the Houdini Primitive
  name for VDBs passed into the OpenVDB AX SOP
- Renamed the OpenVDB AX node type from DN_OpenVDBAX to openvdbax
- Improved the OpenVDB AX SOP UI, added the ability to iterate over
  different value states and the ability to post compact point attributes

AST:
- The Visitor and Modifier have been removed in favour of a new Visitor CRTP
- Introduced AST tokens for type inference
- Introduced implicit parent tracking to AST nodes
- Introduced full and short AST node names
- Converted all child AST nodes to unique pointers from shared pointers
- Introduced child indexing and in-place node replacement
- New token to represent types to avoid passing around strings
- Removed VectorPack/Unpack in favour of ArrayPack/Unpack
- Refactored the crement node to only own a single variable

Grammar:
- Significant clean-up and improvements to lexer and parser
- Removed legacy component assignments in favour of new workflows for point
  and volume vector attributes in their respective code generators
- mat3f, mat3d, mat4f, mat4d, vec2i, vec2f, vec2d, vec4i, vec4f, vec4d, []
  and [,] support
- Improved the operator precedence definitions in the parser
- New variable_reference rule for assignable objects
- Types passed around using new type tokens
- Bison and Flex methods are now all prefixed (with ax) to support multiple
  lexers within the same program
- Removed unused tokens in the lexer
- Improved lexer whitespace support
- Added reserved keywords in the lexer

Code Generation:
- Strings are now represented by a custom LLVM struct which holds a
  re-allocatable char* and an int64_t for the size
- Getters and setters for new attribute type support
- All literals (except for arrays) are passed around as constants and are no
  longer allocated
- String literals are now created as global IR values so that the same
  literals can be shared
- Removed VectorPack/Unpack IR generation in favour of ArrayPack/Unpack
- Updated all visitors to use new AST methods
- Point/volume compute generator no longer overrides crement and assign.
  Instead, attributes are retrieved once at the beginning of the tree and
  set at the end
- Point/volume compute generator create and return their own attribute
  registry to infer read/write accesses
- The volume generator now accepts an additional accessor and index
  representing the volume being accessed
- The function framework now supports nullptr returns for IR functions which
  return void
- Changed the core function storage from void* to void(*)() to adhere to
  point-to-function standard

Compiler:
- Completely removed volume blocks. A single function is generated which is
  run for every volume
- Volume executable updated to support new volume workflow

CMake / Build / Testing:
- Updated to OpenVDB 6.1 CMake modules
- Added CMake support for grammar generation
- Added CMake options for static/shared library generation
- Updated the CMake test framework to run the snippets directly from the
  source repository without copying
- Improved LLVM version support for versions 6/7/8
- Various fixes for clang and MacOS
- Overhaul of frontend tests to compare full AST generation
- Travis improvements including OSX builds
- Travis build matrices for LLVM 5/6/7/8, clang/gcc, osx/linux

Version 0.0.4 - December 12, 2018

Bug fixes:
- Fixed a memory leak in Point and Volume Executable objects.
- Fixed an issue with fit() which could use an incorrect precision for
  floating point arguments.
- Compilation fixes for the Houdini AX SOP for Houdini 15.5 and earlier.

Improvements:
- Added a specialization for print for floats.

Version 0.0.3 - November 13, 2018

New features:
- Introduced new $ syntax and back-end logic for fast lookups into AX Custom
  Data. This syntax works identically to attribute access syntax with type
  specifiers expected to be present when accessing non float data. For
  literal path names, this can be up to x20 faster than using the lookup()
  functions.
- New External Variable AST node, Code Generation/Visitor methods and
  internal intrinsic functions for processing Custom Data lookups using $
  syntax.
- Added a --print-ast command to the vdb_ax binary to output the built AST
  from the provided code snippet.

Improvements:
- Removed the uint64_t LLVM Type specialization as all back-end values are
  signed.
- Introduced a uintptr_t LLVM Type specialization for accessing pointers
  to typed data.
- Consolidated attribute type checking with external variable type checking
  in Compiler.cc into verifyTypedAccesses().
- Minor re-work to the PointDefaultModifier for conversion of default
  attributes.

API Changes:
- ax::print() now takes a const ast::Tree reference.

Houdini:
- External variable $ syntax can now be used to access parameters on the AX
  SOP e.g. ch("parm") -> $parm
- Known path lookups using supported Houdini channel functions (e.g. ch())
  or AX lookup functions are optimized using the new external variable
  syntax for speed gains of up to x20.
- Added optimised access to all available floating points Global and Local
  Node HScript variables such as $F, $T etc.
- Back-ticks are no longer supported as the code is evaluated as a raw
  string. This is to support optimizations for ch() and Houdini HScript $
  parameters. These can be embedded without the need to re-compile the
  string parameter, even if they are time dependent.
- Verbified the AX SOP so that it can be used in compile blocks and as a
  verb through python.

Version 0.0.2 - October 8, 2018

Improvements:
- Added library version naming for libopenvdb_ax.
- Updated Compute Generator initialization methods to leverage the
  function signature framework.
- Improved the usage of CustomData for runtime retrieval of user parameters.
- Add Travis CI support for the core library.
- A variety of comment fixes and improvements.
- Added COPYRIGHT and CHANGES file.

Bug fixes:
- Compilation fixes to the vdb_ax command-line binary.
  [Reported by Elisa Prana]
- Fixed an issue where LLVM would assert due to void pointer instantiation.
  [Reported by Elisa Prana]
- Fixed an issue where MCJIT was not being linked in on some platforms.
  [Reported by Elisa Prana]
- CMake and build fixes for Houdini 17.

API Changes:
- Refactoring of the Compute Functions and their usage within their
  corresponding Executables. Moved a portion of compiler specific code
  into the compiler directory and out of codegen.
- Moved LeafLocalData into the compiler directory.
- Added m prefix to members of CompilerOptions.
- Added a constant shared pointer typedef to CustomData.
- Removed the getFunctionList() compute generator function.
- The CustomData argument for Executable::compiler now has a default empty
  argument and is optional.
- Removed CustomData argument from the ComputeGenerator class constructors.

Version 0.0.1 - August 10 2018 (initial public release)