On Wed, 13 Mar 2024 15:46:30 GMT, Shaojin Wen <d...@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:
>
> bug fix for CharArraySequence
src/java.base/share/classes/java/math/BigDecimal.java line 561:
> 559: index += offset;
> 560: if (index >= length)
> 561: throw new IndexOutOfBoundsException();
This logic is wrong: if offset is 3 and length is 2, aab*bc*c would be valid,
but your code will IOOBE on `charAt(0)` because `index += offset` will be 3, 3
> 2.
You should use `Objects.checkIndex(index, length)` instead.
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PR Review Comment: https://git.openjdk.org/jdk/pull/18177#discussion_r1523540101
