INSTALL

if you want to build the gtsam python library for a specific python version (eg 2.7), use the -DGTSAM_PYTHON_VERSION=2.7 option when running cmake otherwise the default interpreter will be used.
- If the interpreter is inside an environment (such as an anaconda environment or virtualenv environment) then the environment should be active while building gtsam.
This wrapper needs Cython(>=0.25.2), backports_abc>=0.5, and numpy. These can be installed as follows:

 pip install -r <gtsam_folder>/cython/requirements.txt

For compatibility with gtsam's Eigen version, it contains its own cloned version of Eigency, named gtsam_eigency, to interface between C++'s Eigen and Python's numpy.
Build and install gtsam using cmake with GTSAM_INSTALL_CYTHON_TOOLBOX enabled. The wrapped module will be installed to GTSAM_CYTHON_INSTALL_PATH, which is by default: <your CMAKE_INSTALL_PREFIX>/cython
Modify your PYTHONPATH to include the GTSAM_CYTHON_INSTALL_PATH:

export PYTHONPATH=$PYTHONPATH:<GTSAM_CYTHON_INSTALL_PATH>

UNIT TESTS

The Cython toolbox also has a small set of unit tests located in the test directory. To run them:

 cd <your GTSAM_CYTHON_INSTALL_PATH>
 python -m unittest discover

WRITING YOUR OWN SCRIPTS

See the tests for examples.

Some important notes:

Vector/Matrix:
- GTSAM expects double-precision floating point vectors and matrices. Hence, you should pass numpy matrices with dtype=float, or 'float64'.
- Also, GTSAM expects column-major matrices, unlike the default storage scheme in numpy. Hence, you should pass column-major matrices to gtsam using the flag order='F'. And you always get column-major matrices back. For more details, see: https://github.com/wouterboomsma/eigency#storage-layout---why-arrays-are-sometimes-transposed
- Passing row-major matrices of different dtype, e.g. 'int', will also work as the wrapper converts them to column-major and dtype float for you, using numpy.array.astype(float, order='F', copy=False). However, this will result a copy if your matrix is not in the expected type and storage order.
Inner namespace: Classes in inner namespace will be prefixed by _ in Python. Examples: noiseModel_Gaussian, noiseModel_mEstimator_Tukey
Casting from a base class to a derive class must be done explicitly. Examples:

      noiseBase = factor.get_noiseModel()
      noiseGaussian = dynamic_cast_noiseModel_Gaussian_noiseModel_Base(noiseBase)

WRAPPING YOUR OWN PROJECT THAT USES GTSAM

Set PYTHONPATH to include ${GTSAM_CYTHON_INSTALL_PATH}
- so that it can find gtsam Cython header: gtsam/gtsam.pxd
In your CMakeList.txt

find_package(GTSAM REQUIRED) # Make sure gtsam's install folder is in your PATH
set(CMAKE_MODULE_PATH "${CMAKE_MODULE_PATH}" "${GTSAM_DIR}/../GTSAMCMakeTools")

# Wrap
include(GtsamCythonWrap)
include_directories(${GTSAM_EIGENCY_INSTALL_PATH})
wrap_and_install_library_cython("your_project_interface.h"
                                "from gtsam.gtsam cimport *" # extra import of gtsam/gtsam.pxd Cython header
                                "your_install_path"
                                "libraries_to_link_with_the_cython_module"
                                "dependencies_which_need_to_be_built_before_the_wrapper"
                                )
#Optional: install_cython_scripts and install_cython_files. See GtsamCythonWrap.cmake.

KNOWN ISSUES

Doesn't work with python3 installed from homebrew
- size-related issue: can only wrap up to a certain number of classes: up to mEstimator!
- Guess: 64 vs 32b? disutils Compiler flags?
Bug with Cython 0.24: instantiated factor classes return FastVector<size_t> for keys(), which can't be casted to FastVector
- Upgrading to 0.25 solves the problem
Need default constructor and default copy constructor for almost every classes... :(
- support these constructors by default and declare "delete" for special classes?

TODO

☐ allow duplication of parent' functions in child classes. Not allowed for now due to conflicts in Cython. ☐ a common header for boost shared_ptr? (Or wait until everything is switched to std::shared_ptr in gtsam?) ☐ inner namespaces ==> inner packages? ☐ Wrap fixed-size Matrices/Vectors?

Completed/Cancelled:

✔ Fix Python tests: don't use " import * ": Bad style!!! @done (18-03-17 19:50) ✔ Unit tests for cython wrappers @done (18-03-17 18:45) -- simply compare generated files ✔ Wrap unstable @done (18-03-17 15:30) ✔ Unify cython/gtsam.h and the original gtsam.h @done (18-03-17 15:30) ✔ 18-03-17: manage to unify the two versions by removing std container stubs from the matlab version,and keeping KeyList/KeyVector/KeySet as in the matlab version. Probably Cython 0.25 fixes the casting problem. ✔ 06-03-17: manage to remove the requirements for default and copy constructors ✘ 25-11-16: Try to unify but failed. Main reasons are: Key/size_t, std containers, KeyVector/KeyList/KeySet. Matlab doesn't need to know about Key, but I can't make Cython to ignore Key as it couldn't cast KeyVector, i.e. FastVector, to FastVector<size_t>. ✘ Marginal and JointMarginal: revert changes @failed (17-03-17 11:00) -- Cython does need a default constructor! It produces cpp code like this: gtsam::JointMarginal __pyx_t_1; Users don't have to wrap this constructor, however. ✔ Convert input numpy Matrix/Vector to float dtype and storage order 'F' automatically, cannot crash! @done (15-03-17 13:00) ✔ Remove requirements.txt - Frank: don't bother with only 2 packages and a special case for eigency! @done (08-03-17 10:30) ✔ CMake install script @done (25-11-16 02:30) ✘ [REFACTOR] better name for uninstantiateClass: very vague!! @cancelled (25-11-16 02:30) -- lazy ✘ forward declaration? @cancelled (23-11-16 13:00) - nothing to do, seem to work? ✔ wrap VariableIndex: why is it in inference? If need to, shouldn't have constructors to specific FactorGraphs @done (23-11-16 13:00) ✔ Global functions @done (22-11-16 21:00) ✔ [REFACTOR] typesEqual --> isSameSignature @done (22-11-16 21:00) ✔ Proper overloads (constructors, static methods, methods) @done (20-11-16 21:00) ✔ Allow overloading methods. The current solution is annoying!!! @done (20-11-16 21:00) ✔ Casting from parent and grandparents @done (16-11-16 17:00) ✔ Allow overloading constructors. The current solution is annoying!!! @done (16-11-16 17:00) ✔ Support "print obj" @done (16-11-16 17:00) ✔ methods for FastVector: at, [], ... @done (16-11-16 17:00) ✔ Cython: Key and size_t: traits<size_t> doesn't exist @done (16-09-12 18:34) ✔ KeyVector, KeyList, KeySet... @done (16-09-13 17:19) ✔ [Nice to have] parse typedef @done (16-09-13 17:19) ✔ ctypedef at correct places @done (16-09-12 18:34) ✔ expand template variable type in constructor/static methods? @done (16-09-12 18:34) ✔ NonlinearOptimizer: copy constructor deleted!!! @done (16-09-13 17:20) ✔ Value: no default constructor @done (16-09-13 17:20) ✔ ctypedef PriorFactor[Vector] PriorFactorVector @done (16-09-19 12:25) ✔ Delete duplicate methods in derived class @done (16-09-12 13:38) ✔ Fix return properly @done (16-09-11 17:14) ✔ handle pair @done (16-09-11 17:14) ✔ Eigency: ambiguous call: A(const T&) A(const Vector& v) and Eigency A(Map[Vector]& v) @done (16-09-11 07:59) ✔ Eigency: Constructor: ambiguous construct from Vector/Matrix @done (16-09-11 07:59) ✔ Eigency: Fix method template of Vector/Matrix: template argument is [Vector] while arugment is Map[Vector] @done (16-09-11 08:22) ✔ Robust noise: copy assignment operator is deleted because of shared_ptr of the abstract Base class @done (16-09-10 09:05) ✘ Cython: Constructor: generate default constructor? (hack: if it's serializable?) @cancelled (16-09-13 17:20) ✘ Eigency: Map[] to Block @created(16-09-10 07:59) @cancelled (16-09-11 08:28)

inference before symbolic/linear
what's the purpose of "virtual" ??

Installation: ☐ Prerequisite: - Users create venv and pip install requirements before compiling - Wrap cython script in gtsam/cython folder ☐ Install built module into venv?

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