/*
* Copyright (C) 2011 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.math;
import static com.google.common.math.MathTesting.ALL_INTEGER_CANDIDATES;
import static com.google.common.math.MathTesting.ALL_ROUNDING_MODES;
import static com.google.common.math.MathTesting.ALL_SAFE_ROUNDING_MODES;
import static com.google.common.math.MathTesting.EXPONENTS;
import static com.google.common.math.MathTesting.NEGATIVE_INTEGER_CANDIDATES;
import static com.google.common.math.MathTesting.NONZERO_INTEGER_CANDIDATES;
import static com.google.common.math.MathTesting.POSITIVE_INTEGER_CANDIDATES;
import static com.google.common.math.TestPlatform.intsCanGoOutOfRange;
import static java.math.BigInteger.valueOf;
import static java.math.RoundingMode.UNNECESSARY;
import com.google.common.annotations.GwtCompatible;
import junit.framework.TestCase;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.RoundingMode;
/**
* Tests for {@link IntMath}.
*
* @author Louis Wasserman
*/
@GwtCompatible(emulated = true)
public class IntMathTest extends TestCase {
public void testLessThanBranchFree() {
for (int x : ALL_INTEGER_CANDIDATES) {
for (int y : ALL_INTEGER_CANDIDATES) {
if (LongMath.fitsInInt((long) x - y)) {
int expected = (x < y) ? 1 : 0;
int actual = IntMath.lessThanBranchFree(x, y);
assertEquals(expected, actual);
}
}
}
}
public void testLog2ZeroAlwaysThrows() {
for (RoundingMode mode : ALL_ROUNDING_MODES) {
try {
IntMath.log2(0, mode);
fail("Expected IllegalArgumentException");
} catch (IllegalArgumentException expected) {}
}
}
public void testLog2NegativeAlwaysThrows() {
for (int x : NEGATIVE_INTEGER_CANDIDATES) {
for (RoundingMode mode : ALL_ROUNDING_MODES) {
try {
IntMath.log2(x, mode);
fail("Expected IllegalArgumentException");
} catch (IllegalArgumentException expected) {}
}
}
}
// Relies on the correctness of BigIntegrerMath.log2 for all modes except UNNECESSARY.
public void testLog2MatchesBigInteger() {
for (int x : POSITIVE_INTEGER_CANDIDATES) {
for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
assertEquals(BigIntegerMath.log2(valueOf(x), mode), IntMath.log2(x, mode));
}
}
}
// Relies on the correctness of isPowerOfTwo(int).
public void testLog2Exact() {
for (int x : POSITIVE_INTEGER_CANDIDATES) {
// We only expect an exception if x was not a power of 2.
boolean isPowerOf2 = IntMath.isPowerOfTwo(x);
try {
assertEquals(x, 1 << IntMath.log2(x, UNNECESSARY));
assertTrue(isPowerOf2);
} catch (ArithmeticException e) {
assertFalse(isPowerOf2);
}
}
}
// Relies on the correctness of BigIntegerMath.log10 for all modes except UNNECESSARY.
// Relies on the correctness of log10(int, FLOOR) and of pow(int, int).
// Simple test to cover sqrt(0) for all types and all modes.
/* Relies on the correctness of BigIntegerMath.sqrt for all modes except UNNECESSARY. */
/* Relies on the correctness of sqrt(int, FLOOR). */
public void testDivNonZero() {
for (int p : NONZERO_INTEGER_CANDIDATES) {
for (int q : NONZERO_INTEGER_CANDIDATES) {
for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
// Skip some tests that fail due to GWT's non-compliant int implementation.
// TODO(cpovirk): does this test fail for only some rounding modes or for all?
if (p == -2147483648 && q == -1 && intsCanGoOutOfRange()) {
continue;
}
int expected =
new BigDecimal(valueOf(p)).divide(new BigDecimal(valueOf(q)), 0, mode).intValue();
assertEquals(p + "/" + q, force32(expected), IntMath.divide(p, q, mode));
}
}
}
}
public void testDivNonZeroExact() {
for (int p : NONZERO_INTEGER_CANDIDATES) {
for (int q : NONZERO_INTEGER_CANDIDATES) {
// Skip some tests that fail due to GWT's non-compliant int implementation.
if (p == -2147483648 && q == -1 && intsCanGoOutOfRange()) {
continue;
}
boolean dividesEvenly = (p % q) == 0;
try {
assertEquals(p + "/" + q, p, IntMath.divide(p, q, UNNECESSARY) * q);
assertTrue(p + "/" + q + " not expected to divide evenly", dividesEvenly);
} catch (ArithmeticException e) {
assertFalse(p + "/" + q + " expected to divide evenly", dividesEvenly);
}
}
}
}
public void testZeroDivIsAlwaysZero() {
for (int q : NONZERO_INTEGER_CANDIDATES) {
for (RoundingMode mode : ALL_ROUNDING_MODES) {
assertEquals(0, IntMath.divide(0, q, mode));
}
}
}
public void testDivByZeroAlwaysFails() {
for (int p : ALL_INTEGER_CANDIDATES) {
for (RoundingMode mode : ALL_ROUNDING_MODES) {
try {
IntMath.divide(p, 0, mode);
fail("Expected ArithmeticException");
} catch (ArithmeticException expected) {}
}
}
}
public void testMod() {
for (int x : ALL_INTEGER_CANDIDATES) {
for (int m : POSITIVE_INTEGER_CANDIDATES) {
assertEquals(valueOf(x).mod(valueOf(m)).intValue(), IntMath.mod(x, m));
}
}
}
public void testModNegativeModulusFails() {
for (int x : POSITIVE_INTEGER_CANDIDATES) {
for (int m : NEGATIVE_INTEGER_CANDIDATES) {
try {
IntMath.mod(x, m);
fail("Expected ArithmeticException");
} catch (ArithmeticException expected) {}
}
}
}
public void testModZeroModulusFails() {
for (int x : ALL_INTEGER_CANDIDATES) {
try {
IntMath.mod(x, 0);
fail("Expected ArithmeticException");
} catch (ArithmeticException expected) {}
}
}
public void testGCD() {
for (int a : POSITIVE_INTEGER_CANDIDATES) {
for (int b : POSITIVE_INTEGER_CANDIDATES) {
assertEquals(valueOf(a).gcd(valueOf(b)), valueOf(IntMath.gcd(a, b)));
}
}
}
public void testGCDZero() {
for (int a : POSITIVE_INTEGER_CANDIDATES) {
assertEquals(a, IntMath.gcd(a, 0));
assertEquals(a, IntMath.gcd(0, a));
}
assertEquals(0, IntMath.gcd(0, 0));
}
public void testGCDNegativePositiveThrows() {
for (int a : NEGATIVE_INTEGER_CANDIDATES) {
try {
IntMath.gcd(a, 3);
fail("Expected IllegalArgumentException");
} catch (IllegalArgumentException expected) {}
try {
IntMath.gcd(3, a);
fail("Expected IllegalArgumentException");
} catch (IllegalArgumentException expected) {}
}
}
public void testGCDNegativeZeroThrows() {
for (int a : NEGATIVE_INTEGER_CANDIDATES) {
try {
IntMath.gcd(a, 0);
fail("Expected IllegalArgumentException");
} catch (IllegalArgumentException expected) {}
try {
IntMath.gcd(0, a);
fail("Expected IllegalArgumentException");
} catch (IllegalArgumentException expected) {}
}
}
public void testCheckedAdd() {
for (int a : ALL_INTEGER_CANDIDATES) {
for (int b : ALL_INTEGER_CANDIDATES) {
BigInteger expectedResult = valueOf(a).add(valueOf(b));
boolean expectedSuccess = fitsInInt(expectedResult);
try {
assertEquals(a + b, IntMath.checkedAdd(a, b));
assertTrue(expectedSuccess);
} catch (ArithmeticException e) {
assertFalse(expectedSuccess);
}
}
}
}
public void testCheckedSubtract() {
for (int a : ALL_INTEGER_CANDIDATES) {
for (int b : ALL_INTEGER_CANDIDATES) {
BigInteger expectedResult = valueOf(a).subtract(valueOf(b));
boolean expectedSuccess = fitsInInt(expectedResult);
try {
assertEquals(a - b, IntMath.checkedSubtract(a, b));
assertTrue(expectedSuccess);
} catch (ArithmeticException e) {
assertFalse(expectedSuccess);
}
}
}
}
public void testCheckedMultiply() {
for (int a : ALL_INTEGER_CANDIDATES) {
for (int b : ALL_INTEGER_CANDIDATES) {
BigInteger expectedResult = valueOf(a).multiply(valueOf(b));
boolean expectedSuccess = fitsInInt(expectedResult);
try {
assertEquals(a * b, IntMath.checkedMultiply(a, b));
assertTrue(expectedSuccess);
} catch (ArithmeticException e) {
assertFalse(expectedSuccess);
}
}
}
}
public void testCheckedPow() {
for (int b : ALL_INTEGER_CANDIDATES) {
for (int k : EXPONENTS) {
BigInteger expectedResult = valueOf(b).pow(k);
boolean expectedSuccess = fitsInInt(expectedResult);
try {
assertEquals(b + "^" + k, force32(expectedResult.intValue()), IntMath.checkedPow(b, k));
assertTrue(b + "^" + k + " should have succeeded", expectedSuccess);
} catch (ArithmeticException e) {
assertFalse(b + "^" + k + " should have failed", expectedSuccess);
}
}
}
}
// Depends on the correctness of BigIntegerMath.factorial.
public void testFactorial() {
for (int n = 0; n <= 50; n++) {
BigInteger expectedBig = BigIntegerMath.factorial(n);
int expectedInt = fitsInInt(expectedBig) ? expectedBig.intValue() : Integer.MAX_VALUE;
assertEquals(expectedInt, IntMath.factorial(n));
}
}
public void testFactorialNegative() {
for (int n : NEGATIVE_INTEGER_CANDIDATES) {
try {
IntMath.factorial(n);
fail("Expected IllegalArgumentException");
} catch (IllegalArgumentException expected) {}
}
}
// Depends on the correctness of BigIntegerMath.binomial.
/**
* Helper method that asserts the arithmetic mean of x and y is equal
* to the expectedMean.
*/
private static void assertMean(int expectedMean, int x, int y) {
assertEquals("The expectedMean should be the same as computeMeanSafely",
expectedMean, computeMeanSafely(x, y));
assertMean(x, y);
}
/**
* Helper method that asserts the arithmetic mean of x and y is equal
* to the result of computeMeanSafely.
*/
private static void assertMean(int x, int y) {
int expectedMean = computeMeanSafely(x, y);
assertEquals(expectedMean, IntMath.mean(x, y));
assertEquals("The mean of x and y should equal the mean of y and x",
expectedMean, IntMath.mean(y, x));
}
/**
* Computes the mean in a way that is obvious and resilient to
* overflow by using BigInteger arithmetic.
*/
private static int computeMeanSafely(int x, int y) {
BigInteger bigX = BigInteger.valueOf(x);
BigInteger bigY = BigInteger.valueOf(y);
BigDecimal bigMean = new BigDecimal(bigX.add(bigY))
.divide(BigDecimal.valueOf(2), BigDecimal.ROUND_FLOOR);
// parseInt blows up on overflow as opposed to intValue() which does not.
return Integer.parseInt(bigMean.toString());
}
private static boolean fitsInInt(BigInteger big) {
return big.bitLength() <= 31;
}
private static int force32(int value) {
// GWT doesn't consistently overflow values to make them 32-bit, so we need to force it.
return value & 0xffffffff;
}
}