fix checkInvPow2

Author: leerho

src/main/java/org/apache/datasketches/common/Util.java

@@ -445,13 +445,15 @@ public static long ceilingMultiple2expK(final long n, final int k) {
   }
 
   /**
-   * Computes the inverse integer power of 2: 1/(2^e) = 2^(-e).
-   * @param e a positive value between 0 and 1023 inclusive
-   * @return  the inverse integer power of 2: 1/(2^e) = 2^(-e)
+   * Computes the inverse integer power of 2: 1/(2^exp) = 2^(-exp).
+   * @param exp a positive value between 0 and 1023 inclusive
+   * @return the inverse integer power of 2: 1/(2^exp) = 2^(-exp)
    */
-  public static double invPow2(final int e) {
-    assert (e | (1024 - e - 1)) >= 0 : "e cannot be negative or greater than 1023: " + e;
-    return Double.longBitsToDouble((1023L - e) << 52);
+  public static double invPow2(final int exp) {
+    if ((exp | (1024 - exp - 1)) < 0) {
+      throw new SketchesArgumentException("exp cannot be negative or greater than 1023: " + exp);
+    }
+    return Double.longBitsToDouble((1023L - exp) << 52);
   }
 
   /**

src/test/java/org/apache/datasketches/common/UtilTest.java

@@ -203,9 +203,9 @@ public void checkIsMultipleOf8AndGT0() {
   public void checkInvPow2() {
     Assert.assertEquals(invPow2(1), 0.5);
     Assert.assertEquals(invPow2(0), 1.0);
-    try { invPow2(-1); failIAE(); } catch (final AssertionError e) {}
-    try {invPow2(1024); failIAE(); } catch (final AssertionError e) {}
-    try {invPow2(Integer.MIN_VALUE); failIAE(); } catch (final AssertionError e) {}
+    try {invPow2(-1); failIAE(); } catch (final SketchesArgumentException e) {}
+    try {invPow2(1024); failIAE(); } catch (final SketchesArgumentException e) {}
+    try {invPow2(Integer.MIN_VALUE); failIAE(); } catch (final SketchesArgumentException e) {}
   }
 
   private static void failIAE() { throw new IllegalArgumentException("Test should have failed!"); }