Supporting counts from raw samples #2686

theodotk · 2022-06-11T08:54:10Z

Context:

Description of the Change:

Adding the possibility to group samples into counts providing counts=True flag in qml.sample function. This required creation of a new measurement type Counts in measurements.py.

The implementation is based on editing the sample function in _qubit_device.py, though it was possible to base it on estimate_probability function (or to create something new that seems superfluous to me). Choice of editing the sample function seemed more natural for this task, but please tell me if that's not the best approach.

Examples

From the issue:

dev = qml.device('default.qubit', wires=3, shots=10)

@qml.qnode(dev)
def my_circ():
    qml.Hadamard(wires=0)
    qml.CNOT(wires=[0,1])
    qml.PauliX(wires=2) 

    return qml.sample(counts=True)```

```>>> my_counts = my_circ()
>>> print(my_counts)
{'001': 6, '111': 4}

It works also for observables:


@qml.qnode(dev)
def circuit():
    qml.Hadamard(wires=0)
    qml.CNOT(wires=[0, 1])
    return qml.sample(qml.PauliZ(0), counts=True), qml.sample(qml.PauliZ(1), counts=True)```

```>>>result = circuit()
>>>print(result)
[tensor({-1: 472, 1: 528}, dtype=object, requires_grad=True)
 tensor({-1: 472, 1: 528}, dtype=object, requires_grad=True)]

Benefits:

Better visibility of the sampling result.

Possible Drawbacks:

Shouldn't be, as the change scope was minimal.

Related GitHub Issues:
2562

codecov · 2022-06-11T17:14:26Z

Codecov Report

Merging #2686 (0fb203b) into master (38ca383) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #2686   +/-   ##
=======================================
  Coverage   99.61%   99.61%           
=======================================
  Files         255      255           
  Lines       20884    20913   +29     
=======================================
+ Hits        20804    20833   +29     
  Misses         80       80

Impacted Files	Coverage Δ
pennylane/_qubit_device.py	`99.18% <100.00%> (+0.04%)`	⬆️
pennylane/interfaces/autograd.py	`100.00% <100.00%> (ø)`
pennylane/measurements.py	`99.62% <100.00%> (+<0.01%)`	⬆️
pennylane/qnode.py	`100.00% <100.00%> (ø)`

Continue to review full report at Codecov.

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theodotk · 2022-06-14T05:21:41Z

Hey @josh146, can you please re-launch the tests?
I'm also not sure how to interpret code coverage test results and if I can improve it.
Thanks

theodotk · 2022-06-14T18:42:24Z

Thanks @josh146 ! Sorry, I didn't think of checking the tests as well. Can you please relaunch?
Thanks again!

theodotk · 2022-06-14T22:02:50Z

Thanks, @josh146 !
Do you know whom should I ask for a review? The author of the original issue, or there is someone responsible for the measurement/qubit device part of the code?

josh146 · 2022-06-15T01:46:18Z

Thanks @theodotk! Someone from the team will have a look shortly :)

theodotk · 2022-06-16T06:10:21Z

Hey @Jaybsoni @antalszava could you please review the PR?
It's my test assignment for the job interview hence the time limit, and I mention both of you because you are in the initial issue discussion.
Thanks!

Jaybsoni · 2022-06-16T13:58:43Z

Hey @theodotk,

Thanks for the contribution, I will take a look at it today! I think @antalszava will take a closer look at it at some point once he is back in the office as he is overlooking the interview process. Thanks for you patience.

Cheers,

pennylane/_qubit_device.py

Co-authored-by: antalszava <[email protected]>

antalszava · 2022-06-23T22:33:54Z

Hi @theodotk, it seems that changes made in the Autograd interface would be required for other interfaces too because they too cannot interpret dictionaries (e.g., trying to set interface="jax" fails on a jnp.array conversion).

If it doesn't seem to come around, no worries, I could help here tomorrow or latest next week. 👍

theodotk · 2022-06-24T16:01:40Z

Hi @antalszava ! I fixed the problem with jax, and both tensorflow and torch return expected result with the new version.

The problem arose because jax does not handle non-numeric types such as string. And in case of state vector sampling, keys of the counts dictionary are strings (because str is hashable and because converting binary to decimal instead is a less user-friendly option). But the dictionary itself seems to be handled okay.
So the code became slightly uglier 😢 but it works.

Just in case, I chose interface by setting qml.device("default.qubit.jax") (replacing "jax" by "tf" or "torch" for the others). Tell me if it isn't the right way to test.

antalszava · 2022-06-24T17:57:25Z

Hi @theodotk, that's awesome! 🙂

It would be nice then to have a simple example for each interface, e.g.,

import pennylane as qml

dev = qml.device('default.qubit', wires=3, shots=10)

@qml.qnode(dev, inteface="jax")
def circuit():
    return qml.sample(counts=True)

circuit()

and then this PR should be looking great! 🌟

theodotk · 2022-06-24T18:10:37Z

@antalszava you mean in the docs?

antalszava · 2022-06-24T18:27:41Z

@theodotk apologies! I meant such examples as test cases so that we can be sure things are and stay okay. 👍

theodotk · 2022-06-24T21:37:13Z

@antalszava done!

antalszava

Looks good @theodotk! 🥇 Great one with getting each detail right here, thanks for addressing the comments! 🙂

Made a couple of small changes to test docstrings and names, but will merge this soon.

theodotk · 2022-06-25T10:35:32Z

Thanks @antalszava , it is pleasant to see such a diligent review process!

breznychenko added 8 commits June 10, 2022 18:19

counts of raw samples

c4c1fb5

polish

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polish

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polish

76ad5e1

polishing and adapting to pep8

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unit test for Counts measurement type

bd07da0

merging with the current version

02623a2

added the counts into the documentation

e95eac2

theodotk mentioned this pull request Jun 11, 2022

Supporting counts from raw samples #2562

Closed

breznychenko added 4 commits June 11, 2022 22:43

added changelog

c23dd95

black formatting done

907fbd0

docs corrected

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add my name to contributors

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theodotk marked this pull request as draft June 13, 2022 22:19

theodotk marked this pull request as ready for review June 13, 2022 22:19

merge

13d7cc3

breznychenko added 2 commits June 14, 2022 22:19

test: black formatting

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merge doc

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theodotk changed the title ~~Supporting counts from raw samples~~ [WIP] Supporting counts from raw samples Jun 14, 2022

theodotk changed the title ~~[WIP] Supporting counts from raw samples~~ Supporting counts from raw samples Jun 14, 2022

josh146 requested a review from Jaybsoni June 15, 2022 01:45

Merge branch 'master' into master

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Merge branch 'master' into master

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theodotk and others added 3 commits June 22, 2022 21:47

Merge branch 'master' into master

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Merge branch 'master' into master

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Merge branch 'master' into master

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antalszava reviewed Jun 23, 2022

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theodotk and others added 2 commits June 23, 2022 21:56

pennylane/_qubit_device.py: add comment

ea15d23

Co-authored-by: antalszava <[email protected]>

Merge branch 'master' into master

41dde26

breznychenko and others added 3 commits June 24, 2022 17:39

adapt to jax

b3fb571

Merge branch 'master' into master

5c70231

satisfying pylint

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theodotk and others added 2 commits June 24, 2022 18:01

Merge branch 'master' into master

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pennylane/_qubit_device.py sample counts comment expanded

d7ce0c8

Merge branch 'master' into master

7632b02

breznychenko and others added 6 commits June 25, 2022 00:26

sample counts test interfaces

da2887e

polishing

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Merge branch 'master' of https://github.com/theodotk/pennylane

0b8da69

sample counts test interfaces shot vec

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Merge branch 'master' into master

6ba6928

docstrings; test case names

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antalszava approved these changes Jun 25, 2022

View reviewed changes

antalszava merged commit fbda189 into PennyLaneAI:master Jun 25, 2022

This was referenced Jul 20, 2022

Fix cases for qml.sample(..., counts=True) #2839

Merged

Return every outcome with counts (those with 0 counts too) #2864

Closed

lillian542 mentioned this pull request Aug 3, 2022

Add zero count outcomes #2889

Merged

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Supporting counts from raw samples #2686

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Supporting counts from raw samples #2686

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