// ******************************************************************************
   //
   // Title:       Force Field X.
   // Description: Force Field X - Software for Molecular Biophysics.
   // Copyright:   Copyright (c) Michael J. Schnieders 2001-2024.
   //
   // This file is part of Force Field X.
   //
   // Force Field X is free software; you can redistribute it and/or modify it
  // under the terms of the GNU General Public License version 3 as published by
  // the Free Software Foundation.
  //
  // Force Field X is distributed in the hope that it will be useful, but WITHOUT
  // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  // FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
  // details.
  //
  // You should have received a copy of the GNU General Public License along with
  // Force Field X; if not, write to the Free Software Foundation, Inc., 59 Temple
  // Place, Suite 330, Boston, MA 02111-1307 USA
  //
  // Linking this library statically or dynamically with other modules is making a
  // combined work based on this library. Thus, the terms and conditions of the
  // GNU General Public License cover the whole combination.
  //
  // As a special exception, the copyright holders of this library give you
  // permission to link this library with independent modules to produce an
  // executable, regardless of the license terms of these independent modules, and
  // to copy and distribute the resulting executable under terms of your choice,
  // provided that you also meet, for each linked independent module, the terms
  // and conditions of the license of that module. An independent module is a
  // module which is not derived from or based on this library. If you modify this
  // library, you may extend this exception to your version of the library, but
  // you are not obligated to do so. If you do not wish to do so, delete this
  // exception statement from your version.
  //
  // ******************************************************************************
  package ffx.numerics.math;
  
  import static java.lang.Math.sqrt;
  import static org.junit.Assert.assertEquals;
  
  import java.util.Arrays;
  import java.util.Collection;
  
  import ffx.utilities.FFXTest;
  import org.junit.Test;
  import org.junit.runner.RunWith;
  import org.junit.runners.Parameterized;
  import org.junit.runners.Parameterized.Parameters;
  
  /** @author Michael J. Schnieders */
  @RunWith(Parameterized.class)
  public class SquareRootTest extends FFXTest {
  
    private static final double tolerance = 1.0e-13;
    private final String info;
    private final double x;
  
    public SquareRootTest(String info, double x) {
      this.info = info;
      this.x = x;
    }
  
    /** The expected values are found using java.lang.Math.sqrt. */
    @Parameters
    public static Collection<Object[]> data() {
      return Arrays.asList(
          new Object[][] {
            {"Test 1.0e-2", 1.0e-2},
            {"Test 1.0e-1", 1.0e-1},
            {"Test 1.0e0", 1.0e0},
            {"Test 1.0e1", 1.0e1},
            {"Test 1.0e2", 1.0e2},
          });
    }
  
    /** Test inverse sqrt method, of class InverseSqrt. */
    @Test
    public void testInverseSqrt() {
      for (int i = 0; i < 100; i++) {
        double increment = i * x / 10.0;
        double actual = SquareRoot.isqrt(x + increment);
        double expected = 1.0 / sqrt(x + increment);
        assertEquals(info + " + " + increment, expected, actual, tolerance);
      }
    }
  
    /** Test sqrt method, of class InverseSqrt. */
    @Test
    public void testSqrt() {
      for (int i = 0; i < 1000; i++) {
        double increment = i * x / 100.0;
        double actual = SquareRoot.sqrt(x + increment);
        double expected = sqrt(x + increment);
        assertEquals(info + " + " + increment, expected, actual, tolerance);
      }
    }
  }