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add test for weighted search with p > 0.5
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@noajshu
noajshu committed Feb 28, 2024
1 parent e55ae98 commit b6fc313
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Showing 6 changed files with 129 additions and 40 deletions.
45 changes: 34 additions & 11 deletions doc/python_api_reference_vDev.md
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Original file line number Diff line number Diff line change
Expand Up @@ -2452,6 +2452,15 @@ def shortest_error_problem_as_wcnf_file(
"""Generates a maxSAT problem instance in WDIMACS format whose optimal value is
the distance of the protocol, i.e. the minimum weight of any set of errors
that forms an undetectable logical error.
FYI: here is how you could fetch a solver from the
[2023 maxSAT competition](https://maxsat-evaluations.github.io/2023/) and
run the solver on a file produced with this method:
```
# first download nzip CASHWMaxSAT-CorePlus.zip from
# https://maxsat-evaluations.github.io/2023
unzip CASHWMaxSAT-CorePlus.zip
time ./CASHWMaxSAT-CorePlus/bin/cashwmaxsatcoreplus -bm -m problem.wcnf
```
Args:
weighted: Defaults to False (unweighted), so that the problem is to find
Expand All @@ -2473,17 +2482,31 @@ def shortest_error_problem_as_wcnf_file(
Examples:
>>> import stim
>>> circuit = stim.Circuit.generated(
... "surface_code:rotated_memory_x",
... rounds=5,
... distance=5,
... after_clifford_depolarization=0.001)
>>> print(circuit.shortest_undetectable_logical_error_wcnf(
num_distinct_weights=1))
....
>>> print(circuit.shortest_undetectable_logical_error_wcnf(
num_distinct_weights=10))
....
>>> circuit = stim.Circuit("""
... X_ERROR(0.1) 0
... M 0
... OBSERVABLE_INCLUDE(0) rec[-1]
... X_ERROR(0.4) 0
... M 0
... DETECTOR rec[-1] rec[-2]
... """)
>>> print(circuit.shortest_error_problem_as_wcnf_file())
p wcnf 2 4 5
1 -1 0
1 -2 0
5 -1 0
5 2 0
>>>
>>> print(circuit.shortest_error_problem_as_wcnf_file(
... weighted=True,
... num_distinct_weights=10
... ))
p wcnf 2 4 41
2 -1 0
10 -2 0
41 -1 0
41 2 0
"""
```

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45 changes: 34 additions & 11 deletions doc/stim.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -1783,6 +1783,15 @@ class Circuit:
"""Generates a maxSAT problem instance in WDIMACS format whose optimal value is
the distance of the protocol, i.e. the minimum weight of any set of errors
that forms an undetectable logical error.
FYI: here is how you could fetch a solver from the
[2023 maxSAT competition](https://maxsat-evaluations.github.io/2023/) and
run the solver on a file produced with this method:
```
# first download nzip CASHWMaxSAT-CorePlus.zip from
# https://maxsat-evaluations.github.io/2023
unzip CASHWMaxSAT-CorePlus.zip
time ./CASHWMaxSAT-CorePlus/bin/cashwmaxsatcoreplus -bm -m problem.wcnf
```
Args:
weighted: Defaults to False (unweighted), so that the problem is to find
Expand All @@ -1804,17 +1813,31 @@ class Circuit:
Examples:
>>> import stim
>>> circuit = stim.Circuit.generated(
... "surface_code:rotated_memory_x",
... rounds=5,
... distance=5,
... after_clifford_depolarization=0.001)
>>> print(circuit.shortest_undetectable_logical_error_wcnf(
num_distinct_weights=1))
....
>>> print(circuit.shortest_undetectable_logical_error_wcnf(
num_distinct_weights=10))
....
>>> circuit = stim.Circuit("""
... X_ERROR(0.1) 0
... M 0
... OBSERVABLE_INCLUDE(0) rec[-1]
... X_ERROR(0.4) 0
... M 0
... DETECTOR rec[-1] rec[-2]
... """)
>>> print(circuit.shortest_error_problem_as_wcnf_file())
p wcnf 2 4 5
1 -1 0
1 -2 0
5 -1 0
5 2 0
>>>
>>> print(circuit.shortest_error_problem_as_wcnf_file(
... weighted=True,
... num_distinct_weights=10
... ))
p wcnf 2 4 41
2 -1 0
10 -2 0
41 -1 0
41 2 0
"""
def shortest_graphlike_error(
self,
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45 changes: 34 additions & 11 deletions glue/python/src/stim/__init__.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -1783,6 +1783,15 @@ class Circuit:
"""Generates a maxSAT problem instance in WDIMACS format whose optimal value is
the distance of the protocol, i.e. the minimum weight of any set of errors
that forms an undetectable logical error.
FYI: here is how you could fetch a solver from the
[2023 maxSAT competition](https://maxsat-evaluations.github.io/2023/) and
run the solver on a file produced with this method:
```
# first download nzip CASHWMaxSAT-CorePlus.zip from
# https://maxsat-evaluations.github.io/2023
unzip CASHWMaxSAT-CorePlus.zip
time ./CASHWMaxSAT-CorePlus/bin/cashwmaxsatcoreplus -bm -m problem.wcnf
```
Args:
weighted: Defaults to False (unweighted), so that the problem is to find
Expand All @@ -1804,17 +1813,31 @@ class Circuit:
Examples:
>>> import stim
>>> circuit = stim.Circuit.generated(
... "surface_code:rotated_memory_x",
... rounds=5,
... distance=5,
... after_clifford_depolarization=0.001)
>>> print(circuit.shortest_undetectable_logical_error_wcnf(
num_distinct_weights=1))
....
>>> print(circuit.shortest_undetectable_logical_error_wcnf(
num_distinct_weights=10))
....
>>> circuit = stim.Circuit("""
... X_ERROR(0.1) 0
... M 0
... OBSERVABLE_INCLUDE(0) rec[-1]
... X_ERROR(0.4) 0
... M 0
... DETECTOR rec[-1] rec[-2]
... """)
>>> print(circuit.shortest_error_problem_as_wcnf_file())
p wcnf 2 4 5
1 -1 0
1 -2 0
5 -1 0
5 2 0
>>>
>>> print(circuit.shortest_error_problem_as_wcnf_file(
... weighted=True,
... num_distinct_weights=10
... ))
p wcnf 2 4 41
2 -1 0
10 -2 0
41 -1 0
41 2 0
"""
def shortest_graphlike_error(
self,
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3 changes: 2 additions & 1 deletion src/stim/circuit/circuit.pybind.cc
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Expand Up @@ -1986,7 +1986,8 @@ void stim_pybind::pybind_circuit_methods(pybind11::module &, pybind11::class_<Ci
[2023 maxSAT competition](https://maxsat-evaluations.github.io/2023/) and
run the solver on a file produced with this method:
```
wget https://maxsat-evaluations.github.io/2023/mse23-solver-src/exact/CASHWMaxSAT-CorePlus.zip
# first download nzip CASHWMaxSAT-CorePlus.zip from
# https://maxsat-evaluations.github.io/2023
unzip CASHWMaxSAT-CorePlus.zip
time ./CASHWMaxSAT-CorePlus/bin/cashwmaxsatcoreplus -bm -m problem.wcnf
```
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14 changes: 11 additions & 3 deletions src/stim/circuit/circuit_pybind_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -837,11 +837,19 @@ def test_shortest_error_problem_as_wcnf_file():
DETECTOR rec[-1] rec[-2]
""")
wcnf_str = c.shortest_error_problem_as_wcnf_file()
print(wcnf_str)
assert wcnf_str == 'p wcnf 2 4 5\n1 -1 0\n1 -2 0\n5 -1 0\n5 2 0\n'
wcnf_str = c.shortest_error_problem_as_wcnf_file(num_distinct_weights=2)
print(wcnf_str)
wcnf_str = c.shortest_error_problem_as_wcnf_file(weighted=True, num_distinct_weights=2)
assert wcnf_str == 'p wcnf 2 4 9\n1 -1 0\n2 -2 0\n9 -1 0\n9 2 0\n'
c = stim.Circuit("""
X_ERROR(0.1) 0
M 0
OBSERVABLE_INCLUDE(0) rec[-1]
X_ERROR(0.7) 0
M 0
DETECTOR rec[-1] rec[-2]
""")
wcnf_str = c.shortest_error_problem_as_wcnf_file(weighted=True)
assert wcnf_str == 'p wcnf 2 4 5\n1 1 0\n1 -2 0\n5 -1 0\n5 2 0\n'

def test_shortest_graphlike_error_ignore():
c = stim.Circuit("""
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17 changes: 14 additions & 3 deletions src/stim/search/sat/wcnf.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -194,10 +194,21 @@ std::string stim::shortest_error_problem_as_wcnf_file(
observables_flipped[t.val()] = instance.Xor(observables_flipped[t.val()], err_x);
}
}
// Add a soft clause for this error to be inactive
// Add a soft clause for this error
Clause clause;
clause.add_var(~err_x);
clause.weight = -std::log(e.arg_data[0] / (1 - e.arg_data[0]));
double p = e.arg_data[0];
if (!weighted or p <= 0.5) {
// For unweighted search or when the error has probability <= 0.5, the
// soft clause should be that the error is inactive.
clause.add_var(~err_x);
clause.weight = -std::log(p / (1 - p));
} else {
// Invert for weighted search when the probability is > 0.5 and invert
// the weight so that the clause decreases the overall cost when the
// error is active.
clause.add_var(err_x);
clause.weight = -std::log((1 - p) / p);
}
instance.add_clause(clause);
}
++error_index;
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