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Setting instruction duration in transpile seems to do nothing. #6667

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nonhermitian opened this issue Jun 30, 2021 · 3 comments · Fixed by #6799
Closed

Setting instruction duration in transpile seems to do nothing. #6667

nonhermitian opened this issue Jun 30, 2021 · 3 comments · Fixed by #6799
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@Kovi11Day
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bug Something isn't working good first issue Good for newcomers
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0.19

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@nonhermitian
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nonhermitian commented Jun 30, 2021 •
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Information

  • Qiskit Terra version: latest
  • Python version:
  • Operating system:

What is the current behavior?

qc = QuantumCircuit(1)
qc.x(0)
qc.measure_all()

trans_qc = transpile(qc, backend, instruction_durations=[('x', [0], 100000000000000)] )

should take forever to run but it does not.

Steps to reproduce the problem

What is the expected behavior?

I have not seen this feature before, but if it does what it says,

https://qiskit.org/documentation/stubs/qiskit.compiler.transpile.html#qiskit-compiler-transpile

I should be able to modify the duration of instructions. Perhaps this is for pulses only, and the documentation just does not spell this out?

Suggested solutions
@nonhermitian nonhermitian added the bug Something isn't working label Jun 30, 2021
@ajavadia
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ajavadia commented Jul 1, 2021

This will be used if you specify a scheduling_method. I agree the docs should say this.

Alternatively we make the passmanager take this info to mean scheduling is required. This is how e.g. coupling_map and basis_gates are used, even if you don't specify routing_method or translation_method. I think we should go with this.

@ajavadia ajavadia added the good first issue Good for newcomers label Jul 1, 2021
@ajavadia ajavadia mentioned this issue Jul 2, 2021
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@Kovi11Day
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Hello, I am new here, can I look into this issue?

@javabster
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Sure go ahead @Kovi11Day I'll assign to you! Please make sure to refer to the contributing guidelines while working on it. Let us know if you have any questions 😄

Kovi11Day added a commit to Kovi11Day/qiskit-terra that referenced this issue Jul 24, 2021
@Kovi11Day
Fix issue 6667 by updating transpiler
0482266 
Add condition in `qiskit.compiler.transpiler`: if `scheduling_method` is not provided and `instruction_durations` argument specified, set `scheduling_method=as_late_as_possible`.
Note that the `as_late_as_possible` scheduling method was chosen as it is the one applied by default by the scheduler when no method is specified. This scheduling method improves the outcome fidelity over the `as_soon_as_possible` scheduling method.

When the `transpile()` function is provided with the `instruction_durations` argument and no `scheduling_method` argument is specified, the behaviour before update is to ignore the `instruction_durations` argument and not apply any scheduling pass.

After the update, the behaviour is to apply scheduling pass with the default scheduling method: `as_late_as_possible`.

Fixes: Qiskit#6667
@Kovi11Day Kovi11Day mentioned this issue Jul 24, 2021
Merged
Kovi11Day added a commit to Kovi11Day/qiskit-terra that referenced this issue Aug 17, 2021
@Kovi11Day
Fix issue 6667 by updating docstring in transpiler
52f410c 
Update docstring to indicate that the argument `instruction_durations` provided to the `transpile()` function is only applicable if the argument `scheduling_method` is also provided.

Fixes: Qiskit#6667
@mergify mergify bot closed this as completed in #6799 Sep 13, 2021
mergify bot added a commit that referenced this issue Sep 13, 2021
@Kovi11Day @kdk @mergify
Update transpiler documentation of instruction_durations (#6799)
a79709a 
* Fix issue 6667 by updating transpiler

Add condition in `qiskit.compiler.transpiler`: if `scheduling_method` is not provided and `instruction_durations` argument specified, set `scheduling_method=as_late_as_possible`.
Note that the `as_late_as_possible` scheduling method was chosen as it is the one applied by default by the scheduler when no method is specified. This scheduling method improves the outcome fidelity over the `as_soon_as_possible` scheduling method.

When the `transpile()` function is provided with the `instruction_durations` argument and no `scheduling_method` argument is specified, the behaviour before update is to ignore the `instruction_durations` argument and not apply any scheduling pass.

After the update, the behaviour is to apply scheduling pass with the default scheduling method: `as_late_as_possible`.

Fixes: #6667

* Fix issue 6667 by updating docstring in transpiler

Update docstring to indicate that the argument `instruction_durations` provided to the `transpile()` function is only applicable if the argument `scheduling_method` is also provided.

Fixes: #6667

Co-authored-by: Kevin Krsulich <kevin.krsulich@ibm.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
@kdk kdk added this to the 0.19 milestone Nov 15, 2021
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Update transpiler documentation of instruction_durations Kovi11Day/qiskit-terra
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@nonhermitian @kdk @ajavadia @Kovi11Day @javabster