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Added rsqrt() method to the Array class: this method computes the coefficient-wise inverse square root much more efficiently than calling sqrt().inverse().

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This commit is contained in:
Benoit Steiner 2015-12-03 18:16:35 -08:00
parent 029052d276
commit e25e3a041b
2 changed files with 22 additions and 0 deletions
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17
Eigen/src/plugins/ArrayCwiseUnaryOps.h
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@ -4,6 +4,7 @@ typedef CwiseUnaryOp<internal::scalar_abs_op<Scalar>, const Derived> AbsReturnTy
typedef CwiseUnaryOp<internal::scalar_arg_op<Scalar>, const Derived> ArgReturnType; typedef CwiseUnaryOp<internal::scalar_arg_op<Scalar>, const Derived> ArgReturnType;
typedef CwiseUnaryOp<internal::scalar_abs2_op<Scalar>, const Derived> Abs2ReturnType; typedef CwiseUnaryOp<internal::scalar_abs2_op<Scalar>, const Derived> Abs2ReturnType;
typedef CwiseUnaryOp<internal::scalar_sqrt_op<Scalar>, const Derived> SqrtReturnType; typedef CwiseUnaryOp<internal::scalar_sqrt_op<Scalar>, const Derived> SqrtReturnType;
typedef CwiseUnaryOp<internal::scalar_rsqrt_op<Scalar>, const Derived> RsqrtReturnType;
typedef CwiseUnaryOp<internal::scalar_sign_op<Scalar>, const Derived> SignReturnType; typedef CwiseUnaryOp<internal::scalar_sign_op<Scalar>, const Derived> SignReturnType;
typedef CwiseUnaryOp<internal::scalar_inverse_op<Scalar>, const Derived> InverseReturnType; typedef CwiseUnaryOp<internal::scalar_inverse_op<Scalar>, const Derived> InverseReturnType;
typedef CwiseUnaryOp<internal::scalar_boolean_not_op<Scalar>, const Derived> BooleanNotReturnType; typedef CwiseUnaryOp<internal::scalar_boolean_not_op<Scalar>, const Derived> BooleanNotReturnType;
@ -139,6 +140,22 @@ sqrt() const
return SqrtReturnType(derived()); return SqrtReturnType(derived());
} }
/** \returns an expression of the coefficient-wise inverse square root of *this.
*
* This function computes the coefficient-wise inverse square root.
*
* Example: \include Cwise_sqrt.cpp
* Output: \verbinclude Cwise_sqrt.out
*
* \sa pow(), square()
*/
EIGEN_DEVICE_FUNC
inline const RsqrtReturnType
rsqrt() const
{
return RsqrtReturnType(derived());
}
/** \returns an expression of the coefficient-wise signum of *this. /** \returns an expression of the coefficient-wise signum of *this.
* *
* This function computes the coefficient-wise signum. * This function computes the coefficient-wise signum.

5
test/array.cpp
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@ -236,6 +236,7 @@ template<typename ArrayType> void array_real(const ArrayType& m)
// avoid NaNs with abs() so verification doesn't fail // avoid NaNs with abs() so verification doesn't fail
m3 = m1.abs(); m3 = m1.abs();
VERIFY_IS_APPROX(m3.sqrt(), sqrt(abs(m1))); VERIFY_IS_APPROX(m3.sqrt(), sqrt(abs(m1)));
VERIFY_IS_APPROX(m3.rsqrt(), Scalar(1)/sqrt(abs(m1)));
VERIFY_IS_APPROX(m3.log(), log(m3)); VERIFY_IS_APPROX(m3.log(), log(m3));
VERIFY_IS_APPROX(m3.log10(), log10(m3)); VERIFY_IS_APPROX(m3.log10(), log10(m3));
@ -292,6 +293,10 @@ template<typename ArrayType> void array_real(const ArrayType& m)
VERIFY_IS_APPROX(m3.pow(RealScalar(0.5)), m3.sqrt()); VERIFY_IS_APPROX(m3.pow(RealScalar(0.5)), m3.sqrt());
VERIFY_IS_APPROX(pow(m3,RealScalar(0.5)), m3.sqrt()); VERIFY_IS_APPROX(pow(m3,RealScalar(0.5)), m3.sqrt());
VERIFY_IS_APPROX(m3.pow(RealScalar(-0.5)), m3.rsqrt());
VERIFY_IS_APPROX(pow(m3,RealScalar(-0.5)), m3.rsqrt());
VERIFY_IS_APPROX(log10(m3), log(m3)/log(10)); VERIFY_IS_APPROX(log10(m3), log(m3)/log(10));
// scalar by array division // scalar by array division