MATH-1204 bracket function gives up too early

In UnivariateSolverUtils.bracket(...) the search ends prematurely if a =
lowerBound, which ignores some roots in the interval. Fixed by changing the
loop condition so the search continues while b < upperBound. Also added a test
case.

src/main/java/org/apache/commons/math4/analysis/solvers/UnivariateSolverUtils.java

@@ -314,7 +314,7 @@ public class UnivariateSolverUtils {
         double delta = 0;
 
         for (int numIterations = 0;
-             (numIterations < maximumIterations) && (a > lowerBound || b > upperBound);
+             (numIterations < maximumIterations) && (a > lowerBound || b < upperBound);
              ++numIterations) {
 
             final double previousA  = a;

src/test/java/org/apache/commons/math4/analysis/solvers/UnivariateSolverUtilsTest.java

@@ -176,6 +176,14 @@ public class UnivariateSolverUtilsTest {
         UnivariateSolverUtils.bracket(sin, 1.5, 0, 2.0, 0);
     }
 
+    /** check the search continues when a = lowerBound and b < upperBound. */
+    @Test
+    public void testBracketLoopConditionForB() {
+        double[] result = UnivariateSolverUtils.bracket(sin, -0.9, -1, 1, 0.1, 1, 100);
+        Assert.assertTrue(result[0] <= 0);
+        Assert.assertTrue(result[1] >= 0);
+    }
+
     @Test
     public void testMisc() {
         UnivariateFunction f = new QuinticFunction();