On Wed, 2 Oct 2024 10:31:09 GMT, fabioromano1 <d...@openjdk.org> wrote:
> After changing `BigInteger.sqrt()` algorithm, this can be also used to speed > up `BigDecimal.sqrt()` implementation. Here is how I made it. > > The main steps of the algorithm are as follows: > first argument reduce the value to an integer using the following relations: > > x = y * 10 ^ exp > sqrt(x) = sqrt(y) * 10^(exp / 2) if exp is even > sqrt(x) = sqrt(y*10) * 10^((exp-1)/2) is exp is odd > > Then use BigInteger.sqrt() on the reduced value to compute the numerical > digits of the desired result. > > Finally, scale back to the desired exponent range and perform any adjustment > to get the preferred scale in the representation. src/java.base/share/classes/java/math/BigDecimal.java line 2213: > 2211: > 2212: BigDecimal working = new BigDecimal(this.intVal, > this.intCompact, (int) workingScale, this.precision); > 2213: BigInteger workingInt = working.toBigInteger(); @rgiulietti The cause of slow running time starts here: casting to `BigInteger` requires to multiply by a power of 10, and if the power of 10 is large, then the multiplication costs much time, as does computing the square root on the large resulting number. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/21301#discussion_r1784848729
