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 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);
}
}
}