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 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 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 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);
}
}
}
private strictfp double trueLog2(double d) {
double trueLog2 = StrictMath.log(d) / StrictMath.log(2);
// increment until it's >= the true value
while (StrictMath.pow(2.0, trueLog2) < d) {
trueLog2 = StrictMath.nextUp(trueLog2);
}
// decrement until it's <= the true value
while (StrictMath.pow(2.0, trueLog2) > d) {
trueLog2 = StrictMath.nextAfter(trueLog2, Double.NEGATIVE_INFINITY);
}
if (StrictMath.abs(StrictMath.pow(2.0, trueLog2) - d)
> StrictMath.abs(StrictMath.pow(2.0, StrictMath.nextUp(trueLog2)) - d)) {
trueLog2 = StrictMath.nextUp(trueLog2);
}
return trueLog2;
}
public void testIsPowerOfTwoYes() {
for (int i = -1074; i <= 1023; i++) {
assertTrue(DoubleMath.isPowerOfTwo(StrictMath.pow(2.0, i)));
}
}