devtools/eigen
1
0
Fork 0
mirror of https://gitlab.com/libeigen/eigen.git synced 2026-04-10 11:34:33 +08:00
Code Issues Packages Projects Releases Wiki Activity

Avoid inefficient 2x2 LU. Move atanh to internal for maintainability.

Browse Source
This commit is contained in:
Chen-Pang He
2012-08-30 23:40:30 +08:00
parent 9da41cc527
commit d23134e4a7
4 changed files with 51 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
unsupported/Eigen/src/MatrixFunctions/MatrixLogarithm.h
View File

@@ -51,7 +51,6 @@ private:
void compute2x2(const MatrixType& A, MatrixType& result);
void computeBig(const MatrixType& A, MatrixType& result);
static Scalar atanh2(Scalar y, Scalar x);
int getPadeDegree(float normTminusI);
int getPadeDegree(double normTminusI);
int getPadeDegree(long double normTminusI);
@@ -93,20 +92,6 @@ MatrixType MatrixLogarithmAtomic<MatrixType>::compute(const MatrixType& A)
return result;
}
/** \brief Compute atanh (inverse hyperbolic tangent) for \f$ y / x \f$. */
template <typename MatrixType>
typename MatrixType::Scalar MatrixLogarithmAtomic<MatrixType>::atanh2(Scalar y, Scalar x)
{
using std::abs;
using std::sqrt;
Scalar z = y / x;
if (abs(z) > sqrt(NumTraits<Scalar>::epsilon()))
return Scalar(0.5) * log((x + y) / (x - y));
else
return z + z*z*z / Scalar(3);
}
/** \brief Compute logarithm of 2x2 triangular matrix. */
template <typename MatrixType>
void MatrixLogarithmAtomic<MatrixType>::compute2x2(const MatrixType& A, MatrixType& result)
@@ -131,7 +116,7 @@ void MatrixLogarithmAtomic<MatrixType>::compute2x2(const MatrixType& A, MatrixTy
// computation in previous branch is inaccurate if A(1,1) \approx A(0,0)
int unwindingNumber = static_cast<int>(ceil((imag(logA11 - logA00) - M_PI) / (2*M_PI)));
Scalar y = A(1,1) - A(0,0), x = A(1,1) + A(0,0);
result(0,1) = A(0,1) * (Scalar(2) * atanh2(y,x) + Scalar(0,2*M_PI*unwindingNumber)) / y;
result(0,1) = A(0,1) * (Scalar(2) * internal::atanh2(y,x) + Scalar(0,2*M_PI*unwindingNumber)) / y;
}
}