On Tue, 19 Nov 2024 14:44:40 GMT, fabioromano1 <[email protected]> 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.
>
> fabioromano1 has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Correct remainder checking
src/java.base/share/classes/java/math/BigDecimal.java line 2200:
> 2198: // Adjust to requested precision and preferred
> 2199: // scale as appropriate.
> 2200: result = result.adjustToPreferredScale(preferredScale,
> mc.precision);
Suggestion:
return result.adjustToPreferredScale(preferredScale,
mc.precision);
The redundant `else` below can then be removed, resulting in less "indented"
code.
But the current choice is OK as well if you like it better.
src/java.base/share/classes/java/math/BigDecimal.java line 2253:
> 2251:
> 2252: case UP, CEILING -> {
> 2253: BigInteger[] sqrtRem =
> workingInt.sqrtAndRemainder();
Can't this follow the same logic as for the halfway cases, with just `sqrt()`
and a `!workingInt.equals(sqrt.multiply(sqrt))` test? This would increase
consistency.
Are there performance reasons to do it as in the current code?
src/java.base/share/classes/java/math/BigDecimal.java line 2260:
> 2258: }
> 2259:
> 2260: default -> throw new AssertionError("Unexpected
> value for RoundingMode: " + mc.roundingMode);
I think `MatchException` might be better suited (with a `null` cause), but I'll
crosscheck and let you know tomorrow.
src/java.base/share/classes/java/math/BigDecimal.java line 2274:
> 2272: }
> 2273: return result;
> 2274: } else {
As above, this redundant `else` could be removed and the code below be
un-indented a bit. Again, up to your preferences.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/21301#discussion_r1848870665
PR Review Comment: https://git.openjdk.org/jdk/pull/21301#discussion_r1848871435
PR Review Comment: https://git.openjdk.org/jdk/pull/21301#discussion_r1848871866
PR Review Comment: https://git.openjdk.org/jdk/pull/21301#discussion_r1848872056
