public void testRoundLog2Exact() {
for (double x : POSITIVE_FINITE_DOUBLE_CANDIDATES) {
boolean isPowerOfTwo = StrictMath.pow(2.0, DoubleMath.log2(x, FLOOR)) == x;
try {
int log2 = DoubleMath.log2(x, UNNECESSARY);
assertEquals(x, Math.scalb(1.0, log2));
assertTrue(isPowerOfTwo);
} catch (ArithmeticException e) {
assertFalse(isPowerOfTwo);
}
}
}
public void testLog2Accuracy() {
for (double d : POSITIVE_FINITE_DOUBLE_CANDIDATES) {
double dmLog2 = DoubleMath.log2(d);
double trueLog2 = trueLog2(d);
assertTrue(Math.abs(dmLog2 - trueLog2) <= Math.ulp(trueLog2));
}
}
public void testRoundLog2Half() {
// We don't expect perfect rounding accuracy.
for (int exp : asList(-1022, -50, -1, 0, 1, 2, 3, 4, 100, 1022, 1023)) {
for (RoundingMode mode : asList(HALF_EVEN, HALF_UP, HALF_DOWN)) {
double x = Math.scalb(Math.sqrt(2) + 0.001, exp);
double y = Math.scalb(Math.sqrt(2) - 0.001, exp);
if (exp < 0) {
assertEquals(exp + 1, DoubleMath.log2(x, mode));
assertEquals(exp, DoubleMath.log2(y, mode));
} else {
assertEquals(exp + 1, DoubleMath.log2(x, mode));
assertEquals(exp, DoubleMath.log2(y, mode));
}
}
}
}
public void testRoundLog2Floor() {
for (double d : POSITIVE_FINITE_DOUBLE_CANDIDATES) {
int log2 = DoubleMath.log2(d, FLOOR);
assertTrue(StrictMath.pow(2.0, log2) <= d);
assertTrue(StrictMath.pow(2.0, log2 + 1) > d);
}
}
public void testRoundLog2Ceiling() {
for (double d : POSITIVE_FINITE_DOUBLE_CANDIDATES) {
int log2 = DoubleMath.log2(d, CEILING);
assertTrue(StrictMath.pow(2.0, log2) >= d);
double z = StrictMath.pow(2.0, log2 - 1);
assertTrue(z < d);
}
}
public void testIsPowerOfTwo() {
for (double x : ALL_DOUBLE_CANDIDATES) {
boolean expected =
x > 0
&& !Double.isInfinite(x)
&& !Double.isNaN(x)
&& StrictMath.pow(2.0, DoubleMath.log2(x, FLOOR)) == x;
assertEquals(expected, DoubleMath.isPowerOfTwo(x));
}
}
public void testRoundLog2ThrowsOnNegative() {
for (RoundingMode mode : ALL_ROUNDING_MODES) {
for (double d : POSITIVE_FINITE_DOUBLE_CANDIDATES) {
try {
DoubleMath.log2(-d, mode);
fail("Expected IllegalArgumentException");
} catch (IllegalArgumentException e) {
}
}
}
}
public void testRoundLog2ThrowsOnZerosInfinitiesAndNaN() {
for (RoundingMode mode : ALL_ROUNDING_MODES) {
for (double d :
asList(0.0, -0.0, Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY, Double.NaN)) {
try {
DoubleMath.log2(d, mode);
fail("Expected IllegalArgumentException");
} catch (IllegalArgumentException e) {
}
}
}
}
public void testRoundLog2Up() {
for (double d : POSITIVE_FINITE_DOUBLE_CANDIDATES) {
int log2 = DoubleMath.log2(d, UP);
if (d >= 1.0) {
assertTrue(log2 >= 0);
assertTrue(StrictMath.pow(2.0, log2) >= d);
assertTrue(StrictMath.pow(2.0, log2 - 1) < d);
} else {
assertTrue(log2 <= 0);
assertTrue(StrictMath.pow(2.0, log2) <= d);
assertTrue(StrictMath.pow(2.0, log2 + 1) > d);
}
}
}
public void testLog2NaNInfinity() {
assertEquals(Double.POSITIVE_INFINITY, DoubleMath.log2(Double.POSITIVE_INFINITY));
assertTrue(Double.isNaN(DoubleMath.log2(Double.NEGATIVE_INFINITY)));
assertTrue(Double.isNaN(DoubleMath.log2(Double.NaN)));
}
public void testLog2Zero() {
assertEquals(Double.NEGATIVE_INFINITY, DoubleMath.log2(0.0));
assertEquals(Double.NEGATIVE_INFINITY, DoubleMath.log2(-0.0));
}
public void testLog2Negative() {
for (double d : POSITIVE_FINITE_DOUBLE_CANDIDATES) {
assertTrue(Double.isNaN(DoubleMath.log2(-d)));
}
}
public void testLog2SemiMonotonic() {
for (double d : POSITIVE_FINITE_DOUBLE_CANDIDATES) {
assertTrue(DoubleMath.log2(d + 0.01) >= DoubleMath.log2(d));
}
}
