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  1. Commons Math
  2. MATH-204

BrentSolver throws IllegalArgumentException

    Details

    • Type: Bug
    • Status: Closed
    • Priority: Minor
    • Resolution: Fixed
    • Affects Version/s: 1.2
    • Fix Version/s: 2.0
    • Labels:
      None
    • Environment:

      Win XP

      Description

      I am getting this exception:

      java.lang.IllegalArgumentException: Function values at endpoints do not have different signs. Endpoints: [-100000.0,1.7976931348623157E308] Values: [0.0,-101945.04630982173]
      at org.apache.commons.math.analysis.BrentSolver.solve(BrentSolver.java:99)
      at org.apache.commons.math.analysis.BrentSolver.solve(BrentSolver.java:62)

      The exception should not be thrown with values [0.0,-101945.04630982173] because 0.0 is positive.
      According to Brent Worden, the algorithm should stop and return 0 as the root instead of throwing an exception.

      The problem comes from this method:
      public double solve(double min, double max) throws MaxIterationsExceededException,
      FunctionEvaluationException {

      clearResult();
      verifyInterval(min, max);

      double yMin = f.value(min);
      double yMax = f.value(max);

      // Verify bracketing
      if (yMin * yMax >= 0)

      { throw new IllegalArgumentException ("Function values at endpoints do not have different signs." + " Endpoints: [" + min + "," + max + "]" + " Values: [" + yMin + "," + yMax + "]"); }

      // solve using only the first endpoint as initial guess
      return solve(min, yMin, max, yMax, min, yMin);

      }

      One way to fix it would be to add this code after the assignment of yMin and yMax:
      if (yMin ==0 || yMax == 0)

      { return 0; }

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            • Assignee:
              brentworden Brent Worden
              Reporter:
              mickeydog Mick
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              • Created:
                Updated:
                Resolved: