99 lines
13 KiB
Plaintext
99 lines
13 KiB
Plaintext
---
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title: plugin
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description: API reference for qiskit.transpiler.preset_passmanagers.plugin
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in_page_toc_min_heading_level: 2
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python_api_type: module
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python_api_name: qiskit.transpiler.preset_passmanagers.plugin
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---
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<span id="module-qiskit.transpiler.preset_passmanagers.plugin" />
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<span id="qiskit-transpiler-plugins" />
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# Transpiler Stage Plugin Interface
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<span id="module-qiskit.transpiler.preset_passmanagers.plugin" />
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`qiskit.transpiler.preset_passmanagers.plugin`
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This module defines the plugin interface for providing custom stage implementations for the preset pass managers and the [`transpile()`](qiskit.compiler.transpile "qiskit.compiler.transpile") function. This enables external Python packages to provide [`PassManager`](qiskit.transpiler.PassManager "qiskit.transpiler.PassManager") objects that can be used for each named stage.
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The plugin interfaces are built using setuptools [entry points](https://setuptools.readthedocs.io/en/latest/userguide/entry_point.html) which enable packages external to Qiskit to advertise they include a transpiler stage(s).
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For details on how to instead write plugins for transpiler synthesis methods, see [`qiskit.transpiler.passes.synthesis.plugin`](transpiler_synthesis_plugins#module-qiskit.transpiler.passes.synthesis.plugin "qiskit.transpiler.passes.synthesis.plugin").
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<span id="stage-table" />
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## Plugin Stages
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Currently, there are 6 stages in the preset pass managers, all of which actively load external plugins via corresponding entry points.
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| Stage Name | Entry Point | Reserved Names | Description and expectations |
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| -------------- | -------------------------------- | --------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| `init` | `qiskit.transpiler.init` | No reserved names | This stage runs first and is typically used for any initial logical optimization. Because most layout and routing algorithms are only designed to work with 1 and 2 qubit gates, this stage is also used to translate any gates that operate on more than 2 qubits into gates that only operate on 1 or 2 qubits. |
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| `layout` | `qiskit.transpiler.layout` | `trivial`, `dense`, `noise_adaptive`, `sabre` | The output from this stage is expected to have the `layout` property set field set with a [`Layout`](qiskit.transpiler.Layout "qiskit.transpiler.Layout") object. Additionally, the circuit is typically expected to be embedded so that it is expanded to include all qubits and the [`ApplyLayout`](qiskit.transpiler.passes.ApplyLayout "qiskit.transpiler.passes.ApplyLayout") pass is expected to be run to apply the layout. The embedding of the [`Layout`](qiskit.transpiler.Layout "qiskit.transpiler.Layout") can be generated with [`generate_embed_passmanager()`](qiskit.transpiler.preset_passmanagers.common.generate_embed_passmanager "qiskit.transpiler.preset_passmanagers.common.generate_embed_passmanager"). |
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| `routing` | `qiskit.transpiler.routing` | `basic`, `stochastic`, `lookahead`, `sabre`, `toqm` | The output from this stage is expected to have the circuit match the connectivity constraints of the target backend. This does not necessarily need to match the directionality of the edges in the target as a later stage typically will adjust directional gates to match that constraint (but there is no penalty for doing that in the `routing` stage). |
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| `translation` | `qiskit.transpiler.translation` | `translator`, `synthesis`, `unroller` | **The output of this stage is expected to have every operation be a native**instruction on the target backend. |
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| `optimization` | `qiskit.transpiler.optimization` | There are no reserved plugin names | This stage is expected to perform optimization and simplification. The constraints from earlier stages still apply to the output of this stage. After the `optimization` stage is run we expect the circuit to still be executable on the target. |
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| `scheduling` | `qiskit.transpiler.scheduling` | `alap`, `asap` | This is the last stage run and it is expected to output a scheduled circuit such that all idle periods in the circuit are marked by explicit [`Delay`](qiskit.circuit.Delay "qiskit.circuit.Delay") instructions. |
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## Writing Plugins
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To write a pass manager stage plugin there are 2 main steps. The first step is to create a subclass of the abstract plugin class [`PassManagerStagePlugin`](qiskit.transpiler.preset_passmanagers.plugin.PassManagerStagePlugin "qiskit.transpiler.preset_passmanagers.plugin.PassManagerStagePlugin") which is used to define how the [`PassManager`](qiskit.transpiler.PassManager "qiskit.transpiler.PassManager") for the stage will be constructed. For example, to create a `layout` stage plugin that just runs [`VF2Layout`](qiskit.transpiler.passes.VF2Layout "qiskit.transpiler.passes.VF2Layout") (with increasing amount of trials, depending on the optimization level) and falls back to using [`TrivialLayout`](qiskit.transpiler.passes.TrivialLayout "qiskit.transpiler.passes.TrivialLayout") if `VF2Layout` is unable to find a perfect layout:
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```python
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from qiskit.transpiler.preset_passmanagers.plugin import PassManagerStagePlugin
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from qiskit.transpiler.preset_passmanagers import common
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from qiskit.transpiler import PassManager
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from qiskit.transpiler.passes import VF2Layout, TrivialLayout
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from qiskit.transpiler.passes.layout.vf2_layout import VF2LayoutStopReason
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def _vf2_match_not_found(property_set):
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return property_set["layout"] is None or (
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property_set["VF2Layout_stop_reason"] is not None
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and property_set["VF2Layout_stop_reason"] is not VF2LayoutStopReason.SOLUTION_FOUND
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class VF2LayoutPlugin(PassManagerStagePlugin):
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def pass_manager(self, pass_manager_config, optimization_level):
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layout_pm = PassManager(
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[
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VF2Layout(
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coupling_map=pass_manager_config.coupling_map,
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properties=pass_manager_config.backend_properties,
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max_trials=optimization_level * 10 + 1
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target=pass_manager_config.target
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)
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]
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)
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layout_pm.append(
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TrivialLayout(pass_manager_config.coupling_map),
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condition=_vf2_match_not_found,
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)
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layout_pm += common.generate_embed_passmanager(pass_manager_config.coupling_map)
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return layout_pm
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```
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The second step is to expose the [`PassManagerStagePlugin`](qiskit.transpiler.preset_passmanagers.plugin.PassManagerStagePlugin "qiskit.transpiler.preset_passmanagers.plugin.PassManagerStagePlugin") subclass as a setuptools entry point in the package metadata. This can be done by simply adding an `entry_points` entry to the `setuptools.setup` call in the `setup.py` or the plugin package with the necessary entry points under the appropriate namespace for the stage your plugin is for. You can see the list of stages, entry points, and expectations from the stage in [Plugin Stages](#stage-table). For example, continuing from the example plugin above:
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```python
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entry_points = {
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'qiskit.transpiler.layout': [
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'vf2 = qiskit_plugin_pkg.module.plugin:VF2LayoutPlugin',
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]
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},
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```
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Note that the entry point `name = path` is a single string not a Python expression. There isn’t a limit to the number of plugins a single package can include as long as each plugin has a unique name. So a single package can expose multiple plugins if necessary. Refer to [Plugin Stages](#stage-table) for a list of reserved names for each stage.
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## Plugin API
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| | |
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| -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| [`PassManagerStagePlugin`](qiskit.transpiler.preset_passmanagers.plugin.PassManagerStagePlugin "qiskit.transpiler.preset_passmanagers.plugin.PassManagerStagePlugin")() | A `PassManagerStagePlugin` is a plugin interface object for using custom stages in [`transpile()`](qiskit.compiler.transpile "qiskit.compiler.transpile"). |
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| [`PassManagerStagePluginManager`](qiskit.transpiler.preset_passmanagers.plugin.PassManagerStagePluginManager "qiskit.transpiler.preset_passmanagers.plugin.PassManagerStagePluginManager")() | Manager class for preset pass manager stage plugins. |
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| [`list_stage_plugins`](qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins "qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins")(stage\_name) | Get a list of installed plugins for a stage. |
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