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Merged
oberbichler merged 1 commit into from
May 17, 2026
Merged

Guard edge cases #18

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77 changes: 76 additions & 1 deletion include/hypergraph/hypergraph.h
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Original file line number Diff line number Diff line change
Expand Up @@ -14,8 +14,10 @@
#include <tsl/robin_map.h>

#include <algorithm>
#include <cmath>
#include <cstddef>
#include <memory>
#include <stdexcept>

namespace hypergraph {

Expand Down Expand Up @@ -881,6 +883,12 @@ HYPERGRAPH_INLINE Variable<T>& operator*=(Variable<T>& lhs, const double rhs)
template <typename T>
HYPERGRAPH_INLINE Variable<T> inv(const Variable<T>& x)
{
#ifdef HYPERGRAPH_EXCEPTIONS
if (x.value() == 0.0) {
throw std::domain_error("inv: division by zero");
}
#endif

HyperGraph<T>* graph = x.graph();

const auto inv_x = 1.0 / x.value();
Expand Down Expand Up @@ -948,8 +956,14 @@ HYPERGRAPH_INLINE Variable<T> abs(const Variable<T>& x)
{
if (x.value() > 0) {
return x;
} else {
} else if (x.value() < 0) {
return -x;
} else {
// Subgradient convention: abs(0) = 0, d|x|/dx = 0 at x = 0
HyperGraph<T>* graph = x.graph();
const Variable<T> result = graph->new_tmp_variable(0.0);
graph->add_edge(result, x, 0.0, 0.0);
return result;
}
}

Expand All @@ -969,6 +983,15 @@ HYPERGRAPH_INLINE Variable<T> sqrt(const Variable<T>& x)
{
using std::sqrt;

#ifdef HYPERGRAPH_EXCEPTIONS
if (x.value() < 0.0) {
throw std::domain_error("sqrt: negative argument");
}
if (x.value() == 0.0) {
throw std::domain_error("sqrt: derivative undefined at x = 0");
}
#endif

HyperGraph<T>* graph = x.graph();

const auto sqrt_x = sqrt(x.value());
Expand All @@ -983,6 +1006,12 @@ HYPERGRAPH_INLINE Variable<T> pow(const Variable<T>& x, const double a)
{
using std::pow;

#ifdef HYPERGRAPH_EXCEPTIONS
if (x.value() == 0.0 && a < 2.0) {
throw std::domain_error("pow: derivative undefined at x = 0 for exponent < 2");
}
#endif

HyperGraph<T>* graph = x.graph();

const auto pow_x = pow(x.value(), a);
Expand All @@ -1009,6 +1038,12 @@ HYPERGRAPH_INLINE Variable<T> log(const Variable<T>& x)
{
using std::log;

#ifdef HYPERGRAPH_EXCEPTIONS
if (x.value() <= 0.0) {
throw std::domain_error("log: argument must be positive");
}
#endif

HyperGraph<T>* graph = x.graph();

const auto log_x = log(x.value());
Expand Down Expand Up @@ -1052,6 +1087,13 @@ HYPERGRAPH_INLINE Variable<T> tan(const Variable<T>& x)
using std::cos;
using std::tan;

#ifdef HYPERGRAPH_EXCEPTIONS
const auto cos_check = cos(x.value());
if (cos_check == 0.0) {
throw std::domain_error("tan: derivative undefined at x = pi/2 + n*pi");
}
#endif

HyperGraph<T>* graph = x.graph();

const auto tan_x = tan(x.value());
Expand All @@ -1068,6 +1110,12 @@ HYPERGRAPH_INLINE Variable<T> acos(const Variable<T>& x)
using std::acos;
using std::sqrt;

#ifdef HYPERGRAPH_EXCEPTIONS
if (x.value() <= -1.0 || x.value() >= 1.0) {
throw std::domain_error("acos: derivative undefined at |x| >= 1");
}
#endif

HyperGraph<T>* graph = x.graph();

const auto acos_x = acos(x.value());
Expand All @@ -1084,6 +1132,12 @@ HYPERGRAPH_INLINE Variable<T> asin(const Variable<T>& x)
using std::asin;
using std::sqrt;

#ifdef HYPERGRAPH_EXCEPTIONS
if (x.value() <= -1.0 || x.value() >= 1.0) {
throw std::domain_error("asin: derivative undefined at |x| >= 1");
}
#endif

HyperGraph<T>* graph = x.graph();

const auto asin_x = asin(x.value());
Expand Down Expand Up @@ -1172,6 +1226,12 @@ HYPERGRAPH_INLINE Variable<T> acosh(const Variable<T>& x)
using std::acosh;
using std::sqrt;

#ifdef HYPERGRAPH_EXCEPTIONS
if (x.value() <= 1.0) {
throw std::domain_error("acosh: argument must be > 1");
}
#endif

HyperGraph<T>* graph = x.graph();

const auto acosh_x = acosh(x.value());
Expand All @@ -1187,6 +1247,12 @@ HYPERGRAPH_INLINE Variable<T> atanh(const Variable<T>& x)
{
using std::atanh;

#ifdef HYPERGRAPH_EXCEPTIONS
if (x.value() <= -1.0 || x.value() >= 1.0) {
throw std::domain_error("atanh: argument must be in (-1, 1)");
}
#endif

HyperGraph<T>* graph = x.graph();

const auto atanh_x = atanh(x.value());
Expand All @@ -1202,6 +1268,15 @@ HYPERGRAPH_INLINE Variable<T> atan2(const Variable<T>& y, const Variable<T>& x)
{
using std::atan2;

#ifdef HYPERGRAPH_EXCEPTIONS
if (x.value() == 0.0 && y.value() == 0.0) {
throw std::domain_error("atan2: undefined at (0, 0)");
}
if (x.value() == 0.0) {
throw std::domain_error("atan2: derivative undefined at x = 0");
}
#endif

// Use composition atan(y/x) for correct automatic second derivatives.
// The derivatives of atan2(y,x) and atan(y/x) are identical for x != 0.
Variable<T> result = hypergraph::atan(y / x);
Expand Down
111 changes: 111 additions & 0 deletions tests/TestHyperGraph.py
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Original file line number Diff line number Diff line change
Expand Up @@ -663,5 +663,116 @@ def test_out(self):
[0, 0, 0, 0, 0, 7/(9*np.sqrt(6))]])


# edge cases

def test_abs_zero(self):
graph = hg.HyperGraph()

a = graph.new_variable(0)

result = abs(a)
assert_equal(result.value, 0)

graph.compute(result)
g = graph.g()
assert_array_equal(g, [0])

def test_division_by_zero_raises(self):
graph = hg.HyperGraph()

a, b = graph.new_variables([5, 0])

with self.assertRaises(ValueError):
a / b

def test_sqrt_zero_raises(self):
graph = hg.HyperGraph()

a = graph.new_variable(0)

with self.assertRaises(ValueError):
np.sqrt(a)

def test_sqrt_negative_raises(self):
graph = hg.HyperGraph()

a = graph.new_variable(-1)

with self.assertRaises(ValueError):
np.sqrt(a)

def test_log_zero_raises(self):
graph = hg.HyperGraph()

a = graph.new_variable(0)

with self.assertRaises(ValueError):
a.log()

def test_log_negative_raises(self):
graph = hg.HyperGraph()

a = graph.new_variable(-1)

with self.assertRaises(ValueError):
a.log()

def test_asin_boundary_raises(self):
graph = hg.HyperGraph()

a = graph.new_variable(1)

with self.assertRaises(ValueError):
np.arcsin(a)

def test_acos_boundary_raises(self):
graph = hg.HyperGraph()

a = graph.new_variable(-1)

with self.assertRaises(ValueError):
np.arccos(a)

def test_acosh_boundary_raises(self):
graph = hg.HyperGraph()

a = graph.new_variable(1)

with self.assertRaises(ValueError):
a.arccosh()

def test_atanh_boundary_raises(self):
graph = hg.HyperGraph()

a = graph.new_variable(1)

with self.assertRaises(ValueError):
a.arctanh()

def test_pow_zero_low_exponent_raises(self):
graph = hg.HyperGraph()

a = graph.new_variable(0)

with self.assertRaises(ValueError):
a ** 0.5

def test_atan2_origin_raises(self):
graph = hg.HyperGraph()

y, x = graph.new_variables([0, 0])

with self.assertRaises(ValueError):
hg.atan2(y, x)

def test_atan2_x_zero_raises(self):
graph = hg.HyperGraph()

y, x = graph.new_variables([1, 0])

with self.assertRaises(ValueError):
hg.atan2(y, x)


if __name__ == '__main__':
unittest.main()
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