optionals.py

# This code is part of Qiskit.
#
# (C) Copyright IBM 2022.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.

"""
.. currentmodule:: qiskit.utils.optionals

Qiskit Terra, and many of the other Qiskit components, have several features that are enabled only
if certain *optional* dependencies are satisfied.  This module is a collection of objects that can
be used to test if certain functionality is available, and optionally raise
:class:`.MissingOptionalLibraryError` if the functionality is not available.


Available Testers
=================

Qiskit Components
-----------------

.. list-table::
    :widths: 25 75

    * - .. py:data:: HAS_AER
      - :mod:`Qiskit Aer <qiskit.providers.aer>` provides high-performance simulators for the
        quantum circuits constructed within Qiskit Terra.

    * - .. py:data:: HAS_IBMQ
      - The :mod:`Qiskit IBMQ Provider <qiskit.providers.ibmq>` is used for accessing IBM Quantum
        hardware in the IBM cloud.

    * - .. py:data:: HAS_IGNIS
      - :mod:`Qiskit Ignis <qiskit.ignis>` provides tools for quantum hardware verification, noise
        characterization, and error correction.

    * - .. py:data:: HAS_TOQM
      - `Qiskit TOQM <https://github.com/qiskit-toqm/qiskit-toqm>`__ provides transpiler passes
        for the `Time-optimal Qubit mapping algorithm <https://doi.org/10.1145/3445814.3446706>`__.


External Python Libraries
-------------------------

.. list-table::
    :widths: 25 75

    * - .. py:data:: HAS_CONSTRAINT
      - `python-constraint <https://github.com/python-constraint/python-constraint>__ is a
        constraint satisfaction problem solver, used in the :class:`~.CSPLayout` transpiler pass.

    * - .. py:data:: HAS_CPLEX
      - The `IBM CPLEX Optimizer <https://www.ibm.com/analytics/cplex-optimizer>`__ is a
        high-performance mathematical programming solver for linear, mixed-integer and quadratic
        programming.  It is required by the :class:`.BIPMapping` transpiler pass.

    * - .. py:data:: HAS_CVXPY
      - `CVXPY <https://www.cvxpy.org/>`__ is a Python package for solving convex optimization
        problems.  It is required for calculating diamond norms with
        :func:`.quantum_info.diamond_norm`.

    * - .. py:data:: HAS_DOCPLEX
      - `IBM Decision Optimization CPLEX Modelling
        <http://ibmdecisionoptimization.github.io/docplex-doc/>`__ is a library for prescriptive
        analysis.  Like CPLEX, it is required for the :class:`.BIPMapping` transpiler pass.

    * - .. py:data:: HAS_FIXTURES
      - The test suite has additional features that are available if the optional `fixtures
        <https://launchpad.net/python-fixtures>`__ module is installed.  This generally also needs
        :data:`HAS_TESTTOOLS` as well.  This is generally only needed for Qiskit developers.

    * - .. py:data:: HAS_IPYTHON
      - If `the IPython kernel <https://ipython.org/>`__ is available, certain additional
        visualisations and line magics are made available.

    * - .. py:data:: HAS_IPYWIDGETS
      - Monitoring widgets for jobs running on external backends can be provided if `ipywidgets
        <https://ipywidgets.readthedocs.io/en/latest/>`__ is available.

    * - .. py:data:: HAS_JAX
      - Some methods of gradient calculation within :mod:`.opflow.gradients` require `JAX
        <https://github.com/google/jax>`__ for autodifferentiation.

    * - .. py:data:: HAS_MATPLOTLIB
      - Qiskit Terra provides several visualisation tools in the :mod:`.visualization` module.
        Almost all of these are built using `Matplotlib <https://matplotlib.org/>`__, which must
        be installed in order to use them.

    * - .. py:data:: HAS_NETWORKX
      - No longer used by Terra.  Internally, Qiskit now uses the high-performance `rustworkx
        <https://github.com/Qiskit/rustworkx>`__ library as a core dependency, and during the
        change-over period, it was sometimes convenient to convert things into the Python-only
        `NetworkX <https://networkx.org/>`__ format.  Some tests of application modules, such as
        `Qiskit Nature <https://qiskit.org/documentation/nature/>`__ still use NetworkX.

    * - .. py:data:: HAS_NLOPT
      - `NLopt <https://nlopt.readthedocs.io/en/latest/>`__ is a nonlinear optimization library,
        used by the global optimizers in the :mod:`.algorithms.optimizers` module.

    * - .. py:data:: HAS_PIL
      - PIL is a Python image-manipulation library.  Qiskit actually uses the `pillow
        <https://pillow.readthedocs.io/en/stable/>`__ fork of PIL if it is available when generating
        certain visualizations, for example of both :class:`.QuantumCircuit` and
        :class:`.DAGCircuit` in certain modes.

    * - .. py:data:: HAS_PYDOT
      - For some graph visualisations, Qiskit uses `pydot <https://github.com/pydot/pydot>`__ as an
        interface to GraphViz (see :data:`HAS_GRAPHVIZ`).

    * - .. py:data:: HAS_PYLATEX
      - Various LaTeX-based visualizations, especially the circuit drawers, need access to the
        `pylatexenc <https://github.com/phfaist/pylatexenc>`__ project to work correctly.

    * - .. py:data:: HAS_QASM3_IMPORT
      - The functions :func:`.qasm3.load` and :func:`.qasm3.loads` for importing OpenQASM 3 programs
        into :class:`.QuantumCircuit` instances use `an external importer package
        <https://qiskit.github.io/qiskit-qasm3-import>`__.

    * - .. py:data:: HAS_SEABORN
      - Qiskit Terra provides several visualisation tools in the :mod:`.visualization` module.  Some
        of these are built using `Seaborn <https://seaborn.pydata.org/>`__, which must be installed
        in order to use them.

    * - .. py:data:: HAS_SKLEARN
      - Some of the gradient functions in :mod:`.opflow.gradients` use regularisation methods from
        `Scikit Learn <https://scikit-learn.org/stable/>`__.

    * - .. py:data:: HAS_SKQUANT
      - Some of the optimisers in :mod:`.algorithms.optimizers` are based on those found in `Scikit
        Quant <https://github.com/scikit-quant/scikit-quant>`__, which must be installed to use
        them.

    * - .. py:data:: HAS_SQSNOBFIT
      - `SQSnobFit <https://pypi.org/project/SQSnobFit/>`__ is a library for the "stable noisy
        optimization by branch and fit" algorithm.  It is used by the :class:`.SNOBFIT` optimizer.

    * - .. py:data:: HAS_SYMENGINE
      - `Symengine <https://github.com/symengine/symengine>`__ is a fast C++ backend for the
        symbolic-manipulation library `Sympy <https://www.sympy.org/en/index.html>`__.  Qiskit uses
        special methods from Symengine to accelerate its handling of
        :class:`~.circuit.Parameter`\\ s if available.

    * - .. py:data:: HAS_TESTTOOLS
      - Qiskit Terra's test suite has more advanced functionality available if the optional
        `testtools <https://pypi.org/project/testtools/>`__ library is installed.  This is generally
        only needed for Qiskit developers.

    * - .. py:data:: HAS_TWEEDLEDUM
      - `Tweedledum <https://github.com/boschmitt/tweedledum>`__ is an extension library for
        synthesis and optimization of circuits that may involve classical oracles.  Qiskit Terra's
        :class:`.PhaseOracle` uses this, which is used in turn by amplification algorithms via
        the :class:`.AmplificationProblem`.

    * - .. py:data:: HAS_Z3
      - `Z3 <https://github.com/Z3Prover/z3>`__ is a theorem prover, used in the
        :class:`.CrosstalkAdaptiveSchedule` and :class:`.HoareOptimizer` transpiler passes.

External Command-Line Tools
---------------------------

.. list-table::
    :widths: 25 75

    * - .. py:data:: HAS_GRAPHVIZ
      - For some graph visualisations, Qiskit uses the `GraphViz <https://graphviz.org/>`__
        visualisation tool via its ``pydot`` interface (see :data:`HAS_PYDOT`).

    * - .. py:data:: HAS_PDFLATEX
      - Visualisation tools that use LaTeX in their output, such as the circuit drawers, require
        ``pdflatex`` to be available.  You will generally need to ensure that you have a working
        LaTeX installation available, and the ``qcircuit.tex`` package.

    * - .. py:data:: HAS_PDFTOCAIRO
      - Visualisation tools that convert LaTeX-generated files into rasterised images use the
        ``pdftocairo`` tool.  This is part of the `Poppler suite of PDF tools
        <https://poppler.freedesktop.org/>`__.


Lazy Checker Classes
====================

.. currentmodule:: qiskit.utils

Each of the lazy checkers is an instance of :class:`.LazyDependencyManager` in one of its two
subclasses: :class:`.LazyImportTester` and :class:`.LazySubprocessTester`.  These should be imported
from :mod:`.utils` directly if required, such as::

    from qiskit.utils import LazyImportTester

.. autoclass:: qiskit.utils.LazyDependencyManager
    :members:

.. autoclass:: qiskit.utils.LazyImportTester
.. autoclass:: qiskit.utils.LazySubprocessTester
"""

import logging as _logging

from .lazy_tester import (
    LazyImportTester as _LazyImportTester,
    LazySubprocessTester as _LazySubprocessTester,
)

_logger = _logging.getLogger(__name__)

HAS_AER = _LazyImportTester(
    "qiskit.providers.aer",
    name="Qiskit Aer",
    install="pip install qiskit-aer",
)
HAS_IBMQ = _LazyImportTester(
    "qiskit.providers.ibmq",
    name="IBMQ Provider",
    install="pip install qiskit-ibmq-provider",
)
HAS_IGNIS = _LazyImportTester(
    "qiskit.ignis",
    name="Qiskit Ignis",
    install="pip install qiskit-ignis",
)
HAS_TOQM = _LazyImportTester("qiskit_toqm", name="Qiskit TOQM", install="pip install qiskit-toqm")

HAS_CONSTRAINT = _LazyImportTester(
    "constraint",
    name="python-constraint",
    install="pip install python-constraint",
)

HAS_CPLEX = _LazyImportTester(
    "cplex",
    install="pip install 'qiskit-terra[bip-mapper]'",
    msg="This may not be possible for all Python versions and OSes",
)
HAS_CVXPY = _LazyImportTester("cvxpy", install="pip install cvxpy")
HAS_DOCPLEX = _LazyImportTester(
    {"docplex": (), "docplex.mp.model": ("Model",)},
    install="pip install 'qiskit-terra[bip-mapper]'",
    msg="This may not be possible for all Python versions and OSes",
)
HAS_FIXTURES = _LazyImportTester("fixtures", install="pip install fixtures")
HAS_IPYTHON = _LazyImportTester("IPython", install="pip install ipython")
HAS_IPYWIDGETS = _LazyImportTester("ipywidgets", install="pip install ipywidgets")
HAS_JAX = _LazyImportTester(
    {"jax": ("grad", "jit"), "jax.numpy": ()},
    name="jax",
    install="pip install jax",
)
HAS_MATPLOTLIB = _LazyImportTester(
    ("matplotlib.patches", "matplotlib.pyplot"),
    name="matplotlib",
    install="pip install matplotlib",
)
HAS_NETWORKX = _LazyImportTester("networkx", install="pip install networkx")

HAS_NLOPT = _LazyImportTester("nlopt", name="NLopt Optimizer", install="pip install nlopt")
HAS_PIL = _LazyImportTester("PIL.Image", name="pillow", install="pip install pillow")
HAS_PYDOT = _LazyImportTester("pydot", install="pip install pydot")
HAS_PYLATEX = _LazyImportTester(
    {
        "pylatexenc.latex2text": ("LatexNodes2Text",),
        "pylatexenc.latexencode": ("utf8tolatex",),
    },
    name="pylatexenc",
    install="pip install pylatexenc",
)
HAS_QASM3_IMPORT = _LazyImportTester(
    "qiskit_qasm3_import", install="pip install qiskit_qasm3_import"
)
HAS_SEABORN = _LazyImportTester("seaborn", install="pip install seaborn")
HAS_SKLEARN = _LazyImportTester(
    {"sklearn.linear_model": ("Ridge", "Lasso")},
    name="scikit-learn",
    install="pip install scikit-learn",
)
HAS_SKQUANT = _LazyImportTester(
    "skquant.opt",
    name="scikit-quant",
    install="pip install scikit-quant",
)
HAS_SQSNOBFIT = _LazyImportTester("SQSnobFit", install="pip install SQSnobFit")
HAS_SYMENGINE = _LazyImportTester("symengine", install="pip install symengine")
HAS_TESTTOOLS = _LazyImportTester("testtools", install="pip install testtools")
HAS_TWEEDLEDUM = _LazyImportTester("tweedledum", install="pip install tweedledum")
HAS_Z3 = _LazyImportTester("z3", install="pip install z3-solver")

HAS_GRAPHVIZ = _LazySubprocessTester(
    ("dot", "-V"),
    name="graphviz",
    install="'brew install graphviz' if on Mac, or by downloding it from their website",
)
HAS_PDFLATEX = _LazySubprocessTester(
    ("pdflatex", "-version"),
    msg="You will likely need to install a full LaTeX distribution for your system",
)
HAS_PDFTOCAIRO = _LazySubprocessTester(
    ("pdftocairo", "-v"),
    msg="This is part of the 'poppler' set of PDF utilities",
)