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/** @author  André Filipe Caldas Laranjeira
 *  @version 2.0
 *  @note    Fri Sep 15 14:34:10 EDT 2023
 *  @see     LICENSE (MIT style license file).
 *
 *  @note    Data Resulting from a Line Search Step
 */

package scalation
package optimization
package quasi_newton

import scalation.mathstat.VectorD

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/** The `LBFGSLineSearchStep` case class stores the results of a single line search
 *  step performed by a line search algorithm in the implementation of the L-BFGS algorithm.
 *  Every line search algorithm used by the native L-BFGS implementation should return
 *  an instance of this case class upon achieving a successful line search step.
 *
 *  @param x                   `VectorD` representing the values of the variables obtained after
 *                             performing the line search step.
 *  @param g                   `VectorD` representing the gradient vector obtained after performing
 *                             the line search step.
 *  @param fx                  The objective function value obtained after performing the line search step.
 *  @param step                The step selected by the line search algorithm.
 *  @param numberOfIterations  The number of iterations needed to determine the line search step performed.
 */
case class LBFGSLineSearchStep (x: VectorD, g: VectorD, fx: Double, step: Double, numberOfIterations: Int)