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SplineInterpolationBase Class Reference

#include <SplineInterpolationBase.h>

Inheritance diagram for SplineInterpolationBase:
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Public Member Functions

 SplineInterpolationBase ()
 
virtual ~SplineInterpolationBase ()=default
 
Real sample (const std::vector< Real > &x, const std::vector< Real > &y, const std::vector< Real > &y2, Real x_int) const
 
Real sampleDerivative (const std::vector< Real > &x, const std::vector< Real > &y, const std::vector< Real > &y2, Real x_int) const
 
Real sample2ndDerivative (const std::vector< Real > &x, const std::vector< Real > &y, const std::vector< Real > &y2, Real x_int) const
 

Protected Member Functions

void spline (const std::vector< Real > &x, const std::vector< Real > &y, std::vector< Real > &y2, Real yp1=_deriv_bound, Real ypn=_deriv_bound)
 This function calculates the second derivatives based on supplied x and y-vectors. More...
 
void findInterval (const std::vector< Real > &x, Real x_int, unsigned int &klo, unsigned int &khi) const
 
void computeCoeffs (const std::vector< Real > &x, unsigned int klo, unsigned int khi, Real x_int, Real &h, Real &a, Real &b) const
 
Real sample (const std::vector< Real > &x, const std::vector< Real > &y, const std::vector< Real > &y2, Real x_int, unsigned int klo, unsigned int khi) const
 Sample value at point x_int given the indices of the vector of dependent values that bound the point. More...
 

Static Protected Attributes

static const Real _deriv_bound = std::numeric_limits<Real>::max()
 

Detailed Description

Definition at line 17 of file SplineInterpolationBase.h.

Constructor & Destructor Documentation

◆ SplineInterpolationBase()

SplineInterpolationBase::SplineInterpolationBase ( )

Definition at line 16 of file SplineInterpolationBase.C.

16 {}

◆ ~SplineInterpolationBase()

virtual SplineInterpolationBase::~SplineInterpolationBase ( )
virtualdefault

Member Function Documentation

◆ computeCoeffs()

void SplineInterpolationBase::computeCoeffs ( const std::vector< Real > &  x,
unsigned int  klo,
unsigned int  khi,
Real  x_int,
Real &  h,
Real &  a,
Real &  b 
) const
protected

Definition at line 84 of file SplineInterpolationBase.C.

Referenced by sample(), sample2ndDerivative(), and sampleDerivative().

91 {
92  h = x[khi] - x[klo];
93  if (h == 0)
94  mooseError("The values of x must be distinct");
95  a = (x[khi] - x_int) / h;
96  b = (x_int - x[klo]) / h;
97 }
void mooseError(Args &&... args)
Emit an error message with the given stringified, concatenated args and terminate the application...
Definition: MooseError.h:208
static PetscErrorCode Vec x

◆ findInterval()

void SplineInterpolationBase::findInterval ( const std::vector< Real > &  x,
Real  x_int,
unsigned int &  klo,
unsigned int &  khi 
) const
protected

Definition at line 65 of file SplineInterpolationBase.C.

Referenced by BicubicSplineInterpolation::constructColumnSpline(), BicubicSplineInterpolation::constructRowSpline(), sample(), sample2ndDerivative(), and sampleDerivative().

69 {
70  klo = 0;
71  mooseAssert(x.size() >= 2, "You must have at least two knots to create a spline.");
72  khi = x.size() - 1;
73  while (khi - klo > 1)
74  {
75  unsigned int k = (khi + klo) >> 1;
76  if (x[k] > x_int)
77  khi = k;
78  else
79  klo = k;
80  }
81 }
static PetscErrorCode Vec x

◆ sample() [1/2]

Real SplineInterpolationBase::sample ( const std::vector< Real > &  x,
const std::vector< Real > &  y,
const std::vector< Real > &  y2,
Real  x_int 
) const

Definition at line 100 of file SplineInterpolationBase.C.

Referenced by BicubicSplineInterpolation::constructColumnSpline(), BicubicSplineInterpolation::constructRowSpline(), SplineInterpolation::sample(), BicubicSplineInterpolation::sample(), and BicubicSplineInterpolation::sampleValueAndDerivatives().

104 {
105  unsigned int klo, khi;
106  findInterval(x, x_int, klo, khi);
107 
108  return sample(x, y, y2, x_int, klo, khi);
109 }
Real sample(const std::vector< Real > &x, const std::vector< Real > &y, const std::vector< Real > &y2, Real x_int) const
static PetscErrorCode Vec x
void findInterval(const std::vector< Real > &x, Real x_int, unsigned int &klo, unsigned int &khi) const

◆ sample() [2/2]

Real SplineInterpolationBase::sample ( const std::vector< Real > &  x,
const std::vector< Real > &  y,
const std::vector< Real > &  y2,
Real  x_int,
unsigned int  klo,
unsigned int  khi 
) const
protected

Sample value at point x_int given the indices of the vector of dependent values that bound the point.

This method is useful in bicubic spline interpolation, where several spline evaluations are needed to sample from a 2D point.

Definition at line 143 of file SplineInterpolationBase.C.

149 {
150  Real h, a, b;
151  computeCoeffs(x, klo, khi, x_int, h, a, b);
152 
153  return a * y[klo] + b * y[khi] +
154  ((a * a * a - a) * y2[klo] + (b * b * b - b) * y2[khi]) * (h * h) / 6.0;
155 }
void computeCoeffs(const std::vector< Real > &x, unsigned int klo, unsigned int khi, Real x_int, Real &h, Real &a, Real &b) const
static PetscErrorCode Vec x

◆ sample2ndDerivative()

Real SplineInterpolationBase::sample2ndDerivative ( const std::vector< Real > &  x,
const std::vector< Real > &  y,
const std::vector< Real > &  y2,
Real  x_int 
) const

Definition at line 128 of file SplineInterpolationBase.C.

Referenced by SplineInterpolation::sample2ndDerivative(), and BicubicSplineInterpolation::sample2ndDerivative().

132 {
133  unsigned int klo, khi;
134  findInterval(x, x_int, klo, khi);
135 
136  Real h, a, b;
137  computeCoeffs(x, klo, khi, x_int, h, a, b);
138 
139  return a * y2[klo] + b * y2[khi];
140 }
void computeCoeffs(const std::vector< Real > &x, unsigned int klo, unsigned int khi, Real x_int, Real &h, Real &a, Real &b) const
static PetscErrorCode Vec x
void findInterval(const std::vector< Real > &x, Real x_int, unsigned int &klo, unsigned int &khi) const

◆ sampleDerivative()

Real SplineInterpolationBase::sampleDerivative ( const std::vector< Real > &  x,
const std::vector< Real > &  y,
const std::vector< Real > &  y2,
Real  x_int 
) const

Definition at line 112 of file SplineInterpolationBase.C.

Referenced by SplineInterpolation::sampleDerivative(), BicubicSplineInterpolation::sampleDerivative(), and BicubicSplineInterpolation::sampleValueAndDerivatives().

116 {
117  unsigned int klo, khi;
118  findInterval(x, x_int, klo, khi);
119 
120  Real h, a, b;
121  computeCoeffs(x, klo, khi, x_int, h, a, b);
122 
123  return (y[khi] - y[klo]) / h -
124  (((3.0 * a * a - 1.0) * y2[klo] + (3.0 * b * b - 1.0) * -y2[khi]) * h / 6.0);
125 }
void computeCoeffs(const std::vector< Real > &x, unsigned int klo, unsigned int khi, Real x_int, Real &h, Real &a, Real &b) const
static PetscErrorCode Vec x
void findInterval(const std::vector< Real > &x, Real x_int, unsigned int &klo, unsigned int &khi) const

◆ spline()

void SplineInterpolationBase::spline ( const std::vector< Real > &  x,
const std::vector< Real > &  y,
std::vector< Real > &  y2,
Real  yp1 = _deriv_bound,
Real  ypn = _deriv_bound 
)
protected

This function calculates the second derivatives based on supplied x and y-vectors.

Definition at line 19 of file SplineInterpolationBase.C.

Referenced by BicubicSplineInterpolation::constructColumnSpline(), BicubicSplineInterpolation::constructColumnSplineSecondDerivativeTable(), BicubicSplineInterpolation::constructRowSpline(), BicubicSplineInterpolation::constructRowSplineSecondDerivativeTable(), and SplineInterpolation::solve().

24 {
25  auto n = x.size();
26  if (n < 2)
27  mooseError("You must have at least two knots to create a spline.");
28 
29  std::vector<Real> u(n, 0.);
30  y2.assign(n, 0.);
31 
32  if (yp1 >= 1e30)
33  y2[0] = u[0] = 0.;
34  else
35  {
36  y2[0] = -0.5;
37  u[0] = (3.0 / (x[1] - x[0])) * ((y[1] - y[0]) / (x[1] - x[0]) - yp1);
38  }
39  // decomposition of tri-diagonal algorithm (y2 and u are used for temporary storage)
40  for (decltype(n) i = 1; i < n - 1; i++)
41  {
42  Real sig = (x[i] - x[i - 1]) / (x[i + 1] - x[i - 1]);
43  Real p = sig * y2[i - 1] + 2.0;
44  y2[i] = (sig - 1.0) / p;
45  u[i] = (y[i + 1] - y[i]) / (x[i + 1] - x[i]) - (y[i] - y[i - 1]) / (x[i] - x[i - 1]);
46  u[i] = (6.0 * u[i] / (x[i + 1] - x[i - 1]) - sig * u[i - 1]) / p;
47  }
48 
49  Real qn, un;
50  if (ypn >= 1e30)
51  qn = un = 0.;
52  else
53  {
54  qn = 0.5;
55  un = (3.0 / (x[n - 1] - x[n - 2])) * (ypn - (y[n - 1] - y[n - 2]) / (x[n - 1] - x[n - 2]));
56  }
57 
58  y2[n - 1] = (un - qn * u[n - 2]) / (qn * y2[n - 2] + 1.);
59  // back substitution
60  for (auto k = n - 1; k >= 1; k--)
61  y2[k - 1] = y2[k - 1] * y2[k] + u[k - 1];
62 }
void mooseError(Args &&... args)
Emit an error message with the given stringified, concatenated args and terminate the application...
Definition: MooseError.h:208
static PetscErrorCode Vec x
PetscInt n

Member Data Documentation

◆ _deriv_bound

const Real SplineInterpolationBase::_deriv_bound = std::numeric_limits<Real>::max()
staticprotected

Definition at line 75 of file SplineInterpolationBase.h.

Referenced by BicubicSplineInterpolation::errorCheck().


The documentation for this class was generated from the following files: