`postselection_mask` unsupported in sinter v1.14.0

[kaavyas99]

A sinter.Task with a specified postselection_mask parameter compiles and runs successfully when input into sinter.collect with stim==1.13.0 and sinter==1.13.0. However, when both are updated to 1.14.0, the following appears:

ValueError: predictions.shape[0] != num_shots

A relevant code snippet to help demonstrate this:

s_tasks = [
    sinter.Task(circuit=this_circ, postselection_mask=bit_packed_array_for_this_circ_dets)
]

collected_stats: List[sinter.TaskStats] = sinter.collect(
    num_workers=4,
    tasks=s_tasks,
    decoders=['pymatching'],
    max_shots=100_000,
    max_errors=100,
    print_progress=True,
)

This issue may be due to changes made in #804 .

[Strilanc]

Do you have a circuit that triggers this? When I attempt to reproduce it, it works fine:

from typing import List

import numpy as np
import sinter
import stim

if __name__ == '__main__':
    this_circ = stim.Circuit.generated(code_task='surface_code:rotated_memory_x', distance=5, rounds=3)
    bit_packed_array_for_this_circ_dets = np.zeros(shape=(this_circ.num_detectors + 7) // 8, dtype=np.uint8)
    s_tasks = [
        sinter.Task(circuit=this_circ, postselection_mask=bit_packed_array_for_this_circ_dets)
    ]
    
    collected_stats: List[sinter.TaskStats] = sinter.collect(
        num_workers=4,
        tasks=s_tasks,
        decoders=['pymatching'],
        max_shots=1000,
        max_errors=10,
        print_progress=True,
    )

[Strilanc]

Nevermind, got it. Needs to actually postselect some shots.

from typing import List

import numpy as np
import sinter
import stim

if __name__ == '__main__':
    this_circ = stim.Circuit.generated(code_task='surface_code:rotated_memory_x', distance=5, rounds=3, after_clifford_depolarization=0.1)
    bit_packed_array_for_this_circ_dets = np.ones(shape=(this_circ.num_detectors + 7) // 8, dtype=np.uint8)
    s_tasks = [
        sinter.Task(circuit=this_circ, postselection_mask=bit_packed_array_for_this_circ_dets)
    ]
    
    collected_stats: List[sinter.TaskStats] = sinter.collect(
        num_workers=4,
        tasks=s_tasks,
        decoders=['pymatching'],
        max_shots=100000,
        max_errors=1000,
        print_progress=True,
    )

[SchmidtMoritz]

Hi! I just wanted to confirm that this issue is still present when using current versions stim==1.15.0 and sinter==1.15.0.. From what i can tell PR #844 fixes the problem?