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Document DumpLinearLeastSquaresProblem

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Add documentation on the output of DumpLinearLeastSquaresProblem.
This is to clarify confusion brought up on #608

Change-Id: I935cacee1e4345a1d0250aaac322ca2f8e794e66
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brettmichaelgreen
2025-11-08 15:56:10 -05:00
parent 345357a952
commit 0c70ed3a1a
1 changed files with 24 additions and 4 deletions
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docs/source/nnls_solving.rst
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@@ -1987,15 +1987,35 @@ b. ``linear_solver_type = SPARSE_SCHUR/DENSE_SCHUR/ITERATIVE_SCHUR``
* ``TEXTFILE`` Write out the linear least squares problem to the
directory pointed to by
:member:`Solver::Options::trust_region_problem_dump_directory` as
text files which can be read into ``MATLAB/Octave``. The Jacobian
is dumped as a text file containing :math:`(i,j,s)` triplets, the
vectors :math:`D`, `x` and `f` are dumped as text files
containing a list of their values.
text files which can be read into ``MATLAB/Octave``. The
following files are created:
* ``A.txt``: The Jacobian matrix :math:`J` in (i, j, s) triplet format.
* ``b.txt``: The residuals vector :math:`f`.
* ``D.txt``: The diagonal scaling/regularizer matrix.
* ``x.txt``: The computed step vector.
A ``MATLAB/Octave`` script called
``ceres_solver_iteration_???.m`` is also output, which can be
used to parse and load the problem into memory.
.. NOTE::
**Understanding the dumped ``x.txt`` vector:**
The content of ``x.txt`` depends on the
:member:`Solver::Options::trust_region_strategy_type` being
used. This is because the dumping occurs *inside* the
strategy's implementation to gain access to the :math:`D`
matrix:
* If the strategy is ``LEVENBERG_MARQUARDT``, ``x.txt``
contains the **damped trust region step** (the solution
to the scaled problem).
* If the strategy is ``DOGLEG``, ``x.txt`` contains the
**pure, un-damped Gauss-Newton step**. This is *not*
necessarily the final step taken by the optimizer, as it
has not yet been limited by the trust region radius.
.. member:: bool Solver::Options::check_gradients
Default: ``false``