com.opengamma.strata.math.impl.cern.Polynomial Maven / Gradle / Ivy

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/*
 * Copyright (C) 2009 - present by OpenGamma Inc. and the OpenGamma group of companies
 *
 * Please see distribution for license.
 */
/*
 * This code is copied from the original library from the `cern.jet.math` package.
 * Changes:
 * - package name
 * - missing Javadoc param tags
 * - reformat
 * - make package scoped
 */
/*
Copyright � 1999 CERN - European Organization for Nuclear Research.
Permission to use, copy, modify, distribute and sell this software and its documentation for any purpose
is hereby granted without fee, provided that the above copyright notice appear in all copies and
that both that copyright notice and this permission notice appear in supporting documentation.
CERN makes no representations about the suitability of this software for any purpose.
It is provided "as is" without expressed or implied warranty.
*/
package com.opengamma.strata.math.impl.cern;

//CSOFF: ALL
/**
 * Polynomial functions.
 */
class Polynomial extends Constants {
  /**
   * Makes this class non instantiable, but still let's others inherit from it.
   */
  protected Polynomial() {
  }

  /**
   * Evaluates the given polynomial of degree N at x, assuming coefficient of N is 1.0.
   * Otherwise same as polevl().
   *    *                     2          N
   * y  =  C  + C x + C x  +...+ C x
   *        0    1     2          N
   *
   * where C  = 1 and hence is omitted from the array.
   *        N
   *
   * Coefficients are stored in reverse order:
   *
   * coef[0] = C  , ..., coef[N-1] = C  .
   *            N-1                   0
   *
   * Calling arguments are otherwise the same as polevl().
   * 
   * In the interest of speed, there are no checks for out of bounds arithmetic.
   *
   * @param x argument to the polynomial.
   * @param coef the coefficients of the polynomial.
   * @param N the degree of the polynomial.
   * @return result
   * @throws ArithmeticException error
   */
  public static double p1evl(double x, double coef[], int N) throws ArithmeticException {
    double ans;

    ans = x + coef[0];

    for (int i = 1; i < N; i++) {
      ans = ans * x + coef[i];
    }

    return ans;
  }

  /**
   * Evaluates the given polynomial of degree N at x.
   *    *                     2          N
   * y  =  C  + C x + C x  +...+ C x
   *        0    1     2          N
   *
   * Coefficients are stored in reverse order:
   *
   * coef[0] = C  , ..., coef[N] = C  .
   *            N                   0
   * 
   * In the interest of speed, there are no checks for out of bounds arithmetic.
   *
   * @param x argument to the polynomial.
   * @param coef the coefficients of the polynomial.
   * @param N the degree of the polynomial.
   * @return result
   * @throws ArithmeticException error
   */
  public static double polevl(double x, double coef[], int N) throws ArithmeticException {
    double ans;
    ans = coef[0];

    for (int i = 1; i <= N; i++)
      ans = ans * x + coef[i];

    return ans;
  }
}