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bug #977: avoid division by 0 in normalize() and normalized().

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This commit is contained in:
Gael Guennebaud 2016-01-21 20:43:42 +01:00
parent 7cae8918c0
commit ee37eb4eed
2 changed files with 25 additions and 3 deletions
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19
Eigen/src/Core/Dot.h
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@ -102,7 +102,10 @@ inline typename NumTraits<typename internal::traits<Derived>::Scalar>::Real Matr
return numext::sqrt(squaredNorm()); return numext::sqrt(squaredNorm());
} }
/** \returns an expression of the quotient of *this by its own norm. /** \returns an expression of the quotient of \c *this by its own norm.
*
* \warning If the input vector is too small (i.e., this->norm()==0),
* then this function returns a copy of the input.
* *
* \only_for_vectors * \only_for_vectors
* *
@ -114,19 +117,29 @@ MatrixBase<Derived>::normalized() const
{ {
typedef typename internal::nested_eval<Derived,2>::type _Nested; typedef typename internal::nested_eval<Derived,2>::type _Nested;
_Nested n(derived()); _Nested n(derived());
return n / n.norm(); RealScalar z = n.squaredNorm();
// NOTE: after extensive benchmarking, this conditional does not impact performance, at least on recent x86 CPU
if(z>RealScalar(0))
return n / numext::sqrt(z);
else
return n;
} }
/** Normalizes the vector, i.e. divides it by its own norm. /** Normalizes the vector, i.e. divides it by its own norm.
* *
* \only_for_vectors * \only_for_vectors
* *
* \warning If the input vector is too small (i.e., this->norm()==0), then \c *this is left unchanged.
*
* \sa norm(), normalized() * \sa norm(), normalized()
*/ */
template<typename Derived> template<typename Derived>
inline void MatrixBase<Derived>::normalize() inline void MatrixBase<Derived>::normalize()
{ {
*this /= norm(); RealScalar z = squaredNorm();
// NOTE: after extensive benchmarking, this conditional does not impact performance, at least on recent x86 CPU
if(z>RealScalar(0))
derived() /= numext::sqrt(z);
} }
//---------- implementation of other norms ---------- //---------- implementation of other norms ----------

9
test/adjoint.cpp
View File

@ -42,6 +42,15 @@ template<> struct adjoint_specific<false> {
VERIFY_IS_APPROX(v1, v1.norm() * v3); VERIFY_IS_APPROX(v1, v1.norm() * v3);
VERIFY_IS_APPROX(v3, v1.normalized()); VERIFY_IS_APPROX(v3, v1.normalized());
VERIFY_IS_APPROX(v3.norm(), RealScalar(1)); VERIFY_IS_APPROX(v3.norm(), RealScalar(1));
// check null inputs
VERIFY_IS_APPROX((v1*0).normalized(), (v1*0));
RealScalar very_small = (std::numeric_limits<RealScalar>::min)();
VERIFY( (v1*very_small).norm() == 0 );
VERIFY_IS_APPROX((v1*very_small).normalized(), (v1*very_small));
v3 = v1*very_small;
v3.normalize();
VERIFY_IS_APPROX(v3, (v1*very_small));
// check compatibility of dot and adjoint // check compatibility of dot and adjoint
ref = NumTraits<Scalar>::IsInteger ? 0 : (std::max)((std::max)(v1.norm(),v2.norm()),(std::max)((square * v2).norm(),(square.adjoint() * v1).norm())); ref = NumTraits<Scalar>::IsInteger ? 0 : (std::max)((std::max)(v1.norm(),v2.norm()),(std::max)((square * v2).norm(),(square.adjoint() * v1).norm()));