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Reject negative sigma values in noise model constructors #2465

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Merged
dellaert merged 1 commit into from
Mar 12, 2026
+16 −0
Merged

Reject negative sigma values in noise model constructors #2465

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8 changes: 8 additions & 0 deletions gtsam/linear/NoiseModel.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -277,6 +277,10 @@ Diagonal::Diagonal(const Vector& sigmas)
sigmas_(sigmas),
invsigmas_(sigmas.array().inverse()),
precisions_(invsigmas_.array().square()) {
if ((sigmas.array() < 0).any()) {
throw invalid_argument(
"Diagonal noise model: sigma values must be non-negative");
}
}

/* ************************************************************************* */
Expand Down Expand Up @@ -696,12 +700,16 @@ SharedDiagonal Constrained::QR(Matrix& Ab) const {
// Isotropic
/* ************************************************************************* */
Isotropic::shared_ptr Isotropic::Sigma(size_t dim, double sigma, bool smart) {
if (sigma < 0)
throw invalid_argument("Isotropic::Sigma: sigma value must be non-negative");
if (smart && std::abs(sigma-1.0)<1e-9) return Unit::Create(dim);
return shared_ptr(new Isotropic(dim, sigma));
}

/* ************************************************************************* */
Isotropic::shared_ptr Isotropic::Variance(size_t dim, double variance, bool smart) {
if (variance < 0)
throw invalid_argument("Isotropic::Variance: variance must be non-negative");
if (smart && std::abs(variance-1.0)<1e-9) return Unit::Create(dim);
return shared_ptr(new Isotropic(dim, sqrt(variance)));
}
Expand Down
8 changes: 8 additions & 0 deletions gtsam/linear/tests/testNoiseModel.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1074,6 +1074,14 @@ TEST(NoiseModel, NegLogNormalizationConstant3D) {
}
}

/* ************************************************************************* */
// Negative sigma values should throw (#695)
TEST(NoiseModel, NegativeSigmaThrows) {
CHECK_EXCEPTION(noiseModel::Isotropic::Sigma(2, -2.0), std::invalid_argument);
CHECK_EXCEPTION(noiseModel::Isotropic::Variance(2, -1.0), std::invalid_argument);
CHECK_EXCEPTION(noiseModel::Diagonal::Sigmas(Vector3(-1.0, 2.0, 3.0)), std::invalid_argument);
}

/* ************************************************************************* */
int main() { TestResult tr; return TestRegistry::runAllTests(tr); }
/* ************************************************************************* */
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