Author: erans
Date: Wed Oct 30 21:59:57 2013
New Revision: 1537324
URL: http://svn.apache.org/r1537324
Log:
MATH-1047
Added overflow checking to "ArithmeticUtils.pow(long,int)".
Modified:
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/util/ArithmeticUtils.java
commons/proper/math/trunk/src/test/java/org/apache/commons/math3/util/ArithmeticUtilsTest.java
Modified:
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/util/ArithmeticUtils.java
URL:
http://svn.apache.org/viewvc/commons/proper/math/trunk/src/main/java/org/apache/commons/math3/util/ArithmeticUtils.java?rev=1537324&r1=1537323&r2=1537324&view=diff
==============================================================================
---
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/util/ArithmeticUtils.java
(original)
+++
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/util/ArithmeticUtils.java
Wed Oct 30 21:59:57 2013
@@ -706,25 +706,45 @@ public final class ArithmeticUtils {
*
* @param k Number to raise.
* @param e Exponent (must be positive or zero).
- * @return k<sup>e</sup>
+ * @return \( k^e \)
* @throws NotPositiveException if {@code e < 0}.
+ * @throws MathArithmeticException if the result would overflow.
*/
- public static long pow(final long k, int e) throws NotPositiveException {
+ public static long pow(final long k,
+ final int e)
+ throws NotPositiveException,
+ MathArithmeticException {
if (e < 0) {
throw new NotPositiveException(LocalizedFormats.EXPONENT, e);
}
- long result = 1l;
- long k2p = k;
- while (e != 0) {
- if ((e & 0x1) != 0) {
- result *= k2p;
+ try {
+ int exp = e;
+ long result = 1;
+ long k2p = k;
+ while (true) {
+ if ((exp & 0x1) != 0) {
+ result = mulAndCheck(result, k2p);
+ }
+
+ exp >>= 1;
+ if (exp == 0) {
+ break;
+ }
+
+ k2p = mulAndCheck(k2p, k2p);
}
- k2p *= k2p;
- e = e >> 1;
- }
- return result;
+ return result;
+ } catch (MathArithmeticException mae) {
+ // Add context information.
+ mae.getContext().addMessage(LocalizedFormats.OVERFLOW);
+ mae.getContext().addMessage(LocalizedFormats.BASE, k);
+ mae.getContext().addMessage(LocalizedFormats.EXPONENT, e);
+
+ // Rethrow.
+ throw mae;
+ }
}
/**
Modified:
commons/proper/math/trunk/src/test/java/org/apache/commons/math3/util/ArithmeticUtilsTest.java
URL:
http://svn.apache.org/viewvc/commons/proper/math/trunk/src/test/java/org/apache/commons/math3/util/ArithmeticUtilsTest.java?rev=1537324&r1=1537323&r2=1537324&view=diff
==============================================================================
---
commons/proper/math/trunk/src/test/java/org/apache/commons/math3/util/ArithmeticUtilsTest.java
(original)
+++
commons/proper/math/trunk/src/test/java/org/apache/commons/math3/util/ArithmeticUtilsTest.java
Wed Oct 30 21:59:57 2013
@@ -461,29 +461,33 @@ public class ArithmeticUtilsTest {
}
@Test(expected=MathArithmeticException.class)
- public void testPowIntIntOverflow() {
- final int base = 21;
- final int exp = 8;
- ArithmeticUtils.pow(base, exp);
+ public void testPowIntOverflow() {
+ ArithmeticUtils.pow(21, 8);
}
+
@Test
- public void testPowIntIntNoOverflow() {
+ public void testPowInt() {
final int base = 21;
- final int exp = 7;
- ArithmeticUtils.pow(base, exp);
+
+ Assert.assertEquals(85766121L,
+ ArithmeticUtils.pow(base, 6));
+ Assert.assertEquals(1801088541L,
+ ArithmeticUtils.pow(base, 7));
}
@Test(expected=MathArithmeticException.class)
- public void testPowNegativeIntIntOverflow() {
- final int base = -21;
- final int exp = 8;
- ArithmeticUtils.pow(base, exp);
+ public void testPowNegativeIntOverflow() {
+ ArithmeticUtils.pow(-21, 8);
}
+
@Test
- public void testPowNegativeIntIntNoOverflow() {
+ public void testPowNegativeInt() {
final int base = -21;
- final int exp = 7;
- ArithmeticUtils.pow(base, exp);
+
+ Assert.assertEquals(85766121,
+ ArithmeticUtils.pow(base, 6));
+ Assert.assertEquals(-1801088541,
+ ArithmeticUtils.pow(base, 7));
}
@Test
@@ -504,6 +508,54 @@ public class ArithmeticUtilsTest {
}
}
+ @Test(expected=MathArithmeticException.class)
+ public void testPowLongOverflow() {
+ ArithmeticUtils.pow(21, 15);
+ }
+
+ @Test
+ public void testPowLong() {
+ final long base = 21;
+
+ Assert.assertEquals(154472377739119461L,
+ ArithmeticUtils.pow(base, 13));
+ Assert.assertEquals(3243919932521508681L,
+ ArithmeticUtils.pow(base, 14));
+ }
+
+ @Test(expected=MathArithmeticException.class)
+ public void testPowNegativeLongOverflow() {
+ ArithmeticUtils.pow(-21L, 15);
+ }
+
+ @Test
+ public void testPowNegativeLong() {
+ final long base = -21;
+
+ Assert.assertEquals(-154472377739119461L,
+ ArithmeticUtils.pow(base, 13));
+ Assert.assertEquals(3243919932521508681L,
+ ArithmeticUtils.pow(base, 14));
+ }
+
+ @Test
+ public void testPowMinusOneLong() {
+ final long base = -1;
+ for (int i = 0; i < 100; i++) {
+ final long pow = ArithmeticUtils.pow(base, i);
+ Assert.assertEquals("i: " + i, i % 2 == 0 ? 1 : -1, pow);
+ }
+ }
+
+ @Test
+ public void testPowOneLong() {
+ final long base = 1;
+ for (int i = 0; i < 100; i++) {
+ final long pow = ArithmeticUtils.pow(base, i);
+ Assert.assertEquals("i: " + i, 1, pow);
+ }
+ }
+
@Test
public void testIsPowerOfTwo() {
final int n = 1025;
