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refactor: FPE safe eta/theta conversion #3788

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merged 17 commits into from
Nov 7, 2024
Merged

refactor: FPE safe eta/theta conversion #3788

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f6f0767
refactor: FPE safe eta/theta conversion
andiwand Oct 28, 2024
5e130b7
experiment with FPEs
andiwand Oct 28, 2024
2c22146
fix track selector tests
andiwand Oct 28, 2024
e1c3261
use std::floating_point
andiwand Oct 28, 2024
f645945
pr feedback
andiwand Oct 30, 2024
eaf6094
Merge branch 'main' into fpe-safe-eta-theta-conversion
andiwand Oct 31, 2024
2a411cd
provide clamped impl
andiwand Nov 1, 2024
a1cbdbb
test corners
andiwand Nov 1, 2024
aa33d08
Apply suggestions from code review
andiwand Nov 1, 2024
1e56b8c
pr feedback
andiwand Nov 1, 2024
3fd43bc
Merge branch 'fpe-safe-eta-theta-conversion' of github.com:andiwand/a…
andiwand Nov 1, 2024
91e82cb
nuke clamped conversion
andiwand Nov 1, 2024
e8d9d18
drop corner tests
andiwand Nov 1, 2024
5a220d7
Apply suggestions from code review
andiwand Nov 7, 2024
345e426
Update Core/include/Acts/Utilities/AngleHelpers.hpp
andiwand Nov 7, 2024
e5550eb
Update Core/include/Acts/Utilities/AngleHelpers.hpp
andiwand Nov 7, 2024
f92f144
Merge branch 'main' into fpe-safe-eta-theta-conversion
andiwand Nov 7, 2024
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96 changes: 95 additions & 1 deletion Core/include/Acts/Utilities/AngleHelpers.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9,26 +9,120 @@
#pragma once

#include <cmath>
#include <numbers>

namespace Acts::AngleHelpers {

template <typename Scalar>
struct EtaThetaConversionTraits {};

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template <>
struct EtaThetaConversionTraits<float> {
static constexpr float minTheta = 1e-6f;
static constexpr float maxTheta = std::numbers::pi_v<float> - 1e-6f;
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static constexpr float minEta = -80.0f;
static constexpr float maxEta = 80.0f;
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};

template <>
struct EtaThetaConversionTraits<double> {
static constexpr double minTheta = 1e-12;
static constexpr double maxTheta = std::numbers::pi - 1e-12;
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static constexpr double minEta = -700.0;
static constexpr double maxEta = 700.0;
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};

template <typename Scalar>
struct ClampedEtaThetaConversionTraits {
// computed from minEta
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static constexpr Scalar minTheta =
static_cast<Scalar>(3.6097027756908306e-35);
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// computed from maxEta
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static constexpr Scalar maxTheta = static_cast<Scalar>(3.141592653589793);
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static constexpr Scalar minEta = static_cast<Scalar>(-80.0);
static constexpr Scalar maxEta = static_cast<Scalar>(80.0);
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};

/// Calculate the pseudorapidity from the polar angle theta.
///
/// This function aims to be FPE safe and returns infinity for theta values
/// outside the floating point precision range.
///
/// @param theta is the polar angle in radian towards the z-axis.
///
/// @return the pseudorapidity towards the z-axis.
template <typename Scalar>
Scalar etaFromTheta(Scalar theta) {
return -std::log(std::tan(0.5 * theta));
if (theta <= EtaThetaConversionTraits<Scalar>::minTheta) {
return std::numeric_limits<Scalar>::infinity();
}
if (theta >= EtaThetaConversionTraits<Scalar>::maxTheta) {
return -std::numeric_limits<Scalar>::infinity();
}

return -std::log(std::tan(theta / 2));
}
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/// Calculate the polar angle theta from the pseudorapidity.
///
/// This function aims to be FPE safe and returns 0/pi for eta values outside
/// the floating point precision range.
///
/// @param eta is the pseudorapidity towards the z-axis.
///
/// @return the polar angle in radian towards the z-axis.
template <typename Scalar>
Scalar thetaFromEta(Scalar eta) {
if (eta <= EtaThetaConversionTraits<Scalar>::minEta) {
return std::numbers::pi_v<Scalar>;
}
if (eta >= EtaThetaConversionTraits<Scalar>::maxEta) {
return 0;
}

return 2 * std::atan(std::exp(-eta));
}

/// Calculate the pseudorapidity from the polar angle theta.
///
/// This function aims to be FPE safe and returns clamed eta values for theta
/// values outside the defined range.
///
/// @param theta is the polar angle in radian towards the z-axis.
///
/// @return the pseudorapidity towards the z-axis.
template <typename Scalar>
Scalar etaFromThetaClamped(Scalar theta) {
if (theta <= ClampedEtaThetaConversionTraits<Scalar>::minTheta) {
return ClampedEtaThetaConversionTraits<Scalar>::maxEta;
}
if (theta >= ClampedEtaThetaConversionTraits<Scalar>::maxTheta) {
return ClampedEtaThetaConversionTraits<Scalar>::minEta;
}

return -std::log(std::tan(theta / 2));
}

/// Calculate the polar angle theta from the pseudorapidity.
///
/// This function aims to be FPE safe and returns clamed theta values for eta
/// values outside the defined range.
///
/// @param eta is the pseudorapidity towards the z-axis.
///
/// @return the polar angle in radian towards the z-axis.
template <typename Scalar>
Scalar thetaFromEtaClamped(Scalar eta) {
if (eta <= ClampedEtaThetaConversionTraits<Scalar>::minEta) {
return ClampedEtaThetaConversionTraits<Scalar>::maxTheta;
}
if (eta >= ClampedEtaThetaConversionTraits<Scalar>::maxEta) {
return ClampedEtaThetaConversionTraits<Scalar>::minTheta;
}

return 2 * std::atan(std::exp(-eta));
}

Expand Down
73 changes: 35 additions & 38 deletions Tests/UnitTests/Core/TrackFinding/TrackSelectorTests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
#include "Acts/Surfaces/PerigeeSurface.hpp"
#include "Acts/Surfaces/PlaneSurface.hpp"
#include "Acts/TrackFinding/TrackSelector.hpp"
#include "Acts/Utilities/AngleHelpers.hpp"

#include <limits>

Expand Down Expand Up @@ -83,10 +84,6 @@ struct MockTrack {
TrackStateRange trackStatesReversed() const { return {}; }
};

double thetaFromEta(double eta) {
return 2 * std::atan(std::exp(-eta));
}

BOOST_AUTO_TEST_SUITE(TrackSelectorTests)

std::vector<double> etaValues{-5.0, -4.5, -4.0, -3.5, -3.0, -2.5, -2.0, -1.5,
Expand All @@ -97,7 +94,7 @@ BOOST_DATA_TEST_CASE(TestSingleBinCase, bdata::make(etaValues), eta) {
TrackSelector::EtaBinnedConfig cfgBase;

MockTrack baseTrack{};
baseTrack.m_theta = thetaFromEta(eta);
baseTrack.m_theta = AngleHelpers::thetaFromEta(eta);
baseTrack.m_phi = 0.5;
baseTrack.m_pt = 0.5;
baseTrack.m_loc0 = 0.5;
Expand Down Expand Up @@ -206,9 +203,9 @@ BOOST_DATA_TEST_CASE(TestSingleBinCase, bdata::make(etaValues), eta) {
cfg.cutSets.at(0).etaMin = {-1.0};
TrackSelector selector{cfg};
MockTrack track = baseTrack;
track.m_theta = thetaFromEta(0.5);
track.m_theta = AngleHelpers::thetaFromEta(0.5);
BOOST_CHECK(selector.isValidTrack(track));
track.m_theta = thetaFromEta(-1.1);
track.m_theta = AngleHelpers::thetaFromEta(-1.1);
BOOST_CHECK(!selector.isValidTrack(track));
}

Expand All @@ -218,9 +215,9 @@ BOOST_DATA_TEST_CASE(TestSingleBinCase, bdata::make(etaValues), eta) {
cfg.cutSets.at(0).etaMax = {1.0};
TrackSelector selector{cfg};
MockTrack track = baseTrack;
track.m_theta = thetaFromEta(0.5);
track.m_theta = AngleHelpers::thetaFromEta(0.5);
BOOST_CHECK(selector.isValidTrack(track));
track.m_theta = thetaFromEta(1.1);
track.m_theta = AngleHelpers::thetaFromEta(1.1);
BOOST_CHECK(!selector.isValidTrack(track));
}

Expand All @@ -231,11 +228,11 @@ BOOST_DATA_TEST_CASE(TestSingleBinCase, bdata::make(etaValues), eta) {
cfg.cutSets.at(0).etaMax = {1.0};
TrackSelector selector{cfg};
MockTrack track = baseTrack;
track.m_theta = thetaFromEta(0.5);
track.m_theta = AngleHelpers::thetaFromEta(0.5);
BOOST_CHECK(selector.isValidTrack(track));
track.m_theta = thetaFromEta(-1.1);
track.m_theta = AngleHelpers::thetaFromEta(-1.1);
BOOST_CHECK(!selector.isValidTrack(track));
track.m_theta = thetaFromEta(1.1);
track.m_theta = AngleHelpers::thetaFromEta(1.1);
BOOST_CHECK(!selector.isValidTrack(track));
}

Expand All @@ -245,14 +242,14 @@ BOOST_DATA_TEST_CASE(TestSingleBinCase, bdata::make(etaValues), eta) {
cfg.cutSets.at(0).absEtaMin = {0.2};
TrackSelector selector{cfg};
MockTrack track = baseTrack;
track.m_theta = thetaFromEta(0.5);
track.m_theta = AngleHelpers::thetaFromEta(0.5);
BOOST_CHECK(selector.isValidTrack(track));
track.m_theta = thetaFromEta(-0.5);
track.m_theta = AngleHelpers::thetaFromEta(-0.5);
BOOST_CHECK(selector.isValidTrack(track));

track.m_theta = thetaFromEta(0.1);
track.m_theta = AngleHelpers::thetaFromEta(0.1);
BOOST_CHECK(!selector.isValidTrack(track));
track.m_theta = thetaFromEta(-0.1);
track.m_theta = AngleHelpers::thetaFromEta(-0.1);
BOOST_CHECK(!selector.isValidTrack(track));
}

Expand All @@ -262,14 +259,14 @@ BOOST_DATA_TEST_CASE(TestSingleBinCase, bdata::make(etaValues), eta) {
cfg.cutSets.at(0).absEtaMax = {1.0};
TrackSelector selector{cfg};
MockTrack track = baseTrack;
track.m_theta = thetaFromEta(0.5);
track.m_theta = AngleHelpers::thetaFromEta(0.5);
BOOST_CHECK(selector.isValidTrack(track));
track.m_theta = thetaFromEta(-0.5);
track.m_theta = AngleHelpers::thetaFromEta(-0.5);
BOOST_CHECK(selector.isValidTrack(track));

track.m_theta = thetaFromEta(1.1);
track.m_theta = AngleHelpers::thetaFromEta(1.1);
BOOST_CHECK(!selector.isValidTrack(track));
track.m_theta = thetaFromEta(-1.1);
track.m_theta = AngleHelpers::thetaFromEta(-1.1);
BOOST_CHECK(!selector.isValidTrack(track));
}

Expand All @@ -280,19 +277,19 @@ BOOST_DATA_TEST_CASE(TestSingleBinCase, bdata::make(etaValues), eta) {
cfg.cutSets.at(0).absEtaMax = {1.0};
TrackSelector selector{cfg};
MockTrack track = baseTrack;
track.m_theta = thetaFromEta(0.5);
track.m_theta = AngleHelpers::thetaFromEta(0.5);
BOOST_CHECK(selector.isValidTrack(track));
track.m_theta = thetaFromEta(-0.5);
track.m_theta = AngleHelpers::thetaFromEta(-0.5);
BOOST_CHECK(selector.isValidTrack(track));

track.m_theta = thetaFromEta(0.1);
track.m_theta = AngleHelpers::thetaFromEta(0.1);
BOOST_CHECK(!selector.isValidTrack(track));
track.m_theta = thetaFromEta(-0.1);
track.m_theta = AngleHelpers::thetaFromEta(-0.1);
BOOST_CHECK(!selector.isValidTrack(track));

track.m_theta = thetaFromEta(1.1);
track.m_theta = AngleHelpers::thetaFromEta(1.1);
BOOST_CHECK(!selector.isValidTrack(track));
track.m_theta = thetaFromEta(-1.1);
track.m_theta = AngleHelpers::thetaFromEta(-1.1);
BOOST_CHECK(!selector.isValidTrack(track));
}

Expand Down Expand Up @@ -373,27 +370,27 @@ BOOST_AUTO_TEST_CASE(TestSingleBinEtaCutByBinEdge) {
BOOST_TEST_INFO_SCOPE(selector.config());

MockTrack track{};
track.m_theta = thetaFromEta(0.0);
track.m_theta = AngleHelpers::thetaFromEta(0.0);
BOOST_CHECK(!selector.isValidTrack(track));

track.m_theta = thetaFromEta(0.5);
track.m_theta = AngleHelpers::thetaFromEta(0.5);
BOOST_CHECK(!selector.isValidTrack(track));

// cannot easily check on-edge behavior because of floating point arithmetic
// (it won't be exactly 1.0 in selector)
track.m_theta = thetaFromEta(1.01);
track.m_theta = AngleHelpers::thetaFromEta(1.01);
BOOST_CHECK(selector.isValidTrack(track));

track.m_theta = thetaFromEta(1.5);
track.m_theta = AngleHelpers::thetaFromEta(1.5);
BOOST_CHECK(selector.isValidTrack(track));

track.m_theta = thetaFromEta(2.0);
track.m_theta = AngleHelpers::thetaFromEta(2.0);
BOOST_CHECK(!selector.isValidTrack(track));
}

BOOST_AUTO_TEST_CASE(TestMultiBinCuts) {
MockTrack baseTrack{};
baseTrack.m_theta = thetaFromEta(1.0);
baseTrack.m_theta = AngleHelpers::thetaFromEta(1.0);
baseTrack.m_phi = 0.5;
baseTrack.m_pt = 0.5;
baseTrack.m_loc0 = 0.5;
Expand Down Expand Up @@ -425,7 +422,7 @@ BOOST_AUTO_TEST_CASE(TestMultiBinCuts) {
{
// exactly at zero
MockTrack track = baseTrack;
track.m_theta = thetaFromEta(0.0);
track.m_theta = AngleHelpers::thetaFromEta(0.0);

BOOST_CHECK(selector.isValidTrack(track));

Expand All @@ -439,7 +436,7 @@ BOOST_AUTO_TEST_CASE(TestMultiBinCuts) {
{
// first bin
MockTrack track = baseTrack;
track.m_theta = thetaFromEta(1.0);
track.m_theta = AngleHelpers::thetaFromEta(1.0);

BOOST_CHECK(selector.isValidTrack(track));

Expand All @@ -453,8 +450,8 @@ BOOST_AUTO_TEST_CASE(TestMultiBinCuts) {
{
// first bin edge
MockTrack track = baseTrack;
track.m_theta =
thetaFromEta(2.0 - std::numeric_limits<double>::epsilon());
track.m_theta = AngleHelpers::thetaFromEta(
2.0 - std::numeric_limits<double>::epsilon());
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BOOST_CHECK(selector.isValidTrack(track));

Expand All @@ -468,7 +465,7 @@ BOOST_AUTO_TEST_CASE(TestMultiBinCuts) {
{
// second bin lower edge
MockTrack track = baseTrack;
track.m_theta = thetaFromEta(2.0);
track.m_theta = AngleHelpers::thetaFromEta(2.0);

BOOST_CHECK(selector.isValidTrack(track));

Expand All @@ -488,7 +485,7 @@ BOOST_AUTO_TEST_CASE(TestMultiBinCuts) {
{
// second bin
MockTrack track = baseTrack;
track.m_theta = thetaFromEta(666.0);
track.m_theta = AngleHelpers::thetaFromEta(10.0);

track.*prop = -1.1;
BOOST_CHECK(selector.isValidTrack(track));
Expand Down
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