RFR: 8327791: Optimization for new BigDecimal(String) [v8]
Claes Redestad
redestad at openjdk.org
Tue Mar 12 12:17:16 UTC 2024
On Tue, 12 Mar 2024 10:34:33 GMT, Shaojin Wen <duke at openjdk.org> wrote:
>> The current BigDecimal(String) constructor calls String#toCharArray, which has a memory allocation.
>>
>>
>> public BigDecimal(String val) {
>> this(val.toCharArray(), 0, val.length()); // allocate char[]
>> }
>>
>>
>> When the length is greater than 18, create a char[]
>>
>>
>> boolean isCompact = (len <= MAX_COMPACT_DIGITS); // 18
>> if (!isCompact) {
>> // ...
>> } else {
>> char[] coeff = new char[len]; // allocate char[]
>> // ...
>> }
>>
>>
>> This PR eliminates the two memory allocations mentioned above, resulting in an approximate 60% increase in performance..
>
> Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:
>
> refactor CharArraySequence
src/java.base/share/classes/java/math/BigInteger.java line 628:
> 626: // Pre-allocate array of expected size
> 627: int numWords;
> 628: if (len < 10) {
IMHO removing these curly braces just adds noise to the PR and change history.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/18177#discussion_r1521356886
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