René Kanters wrote:
> Interesting question.
>
> I would think that the compiler may not be able to optimize that since
> if any function is called it may modify the JpegObj.VsampFactor[comp]
> value (possibly as a side-effect only) in which case the loop should
> have a different high end cutoff.
>
> I wonder whether it may be better to count down in stead, which I
> vaguely recall Miguel once suggested in an email on Java coding styles.
>
I've started to use the count-down quite a bit:
for(i = JpegObj.VsampFactor[comp]; --i >=0;) {
for(j =JpegObj.HsampFactor[comp];--j >=0) {
Very compact.
on something like this, which might go a million times, it seems to me
worth it to optimize a bit.
Bob
> René
>
> On May 14, 2007, at 5:38 PM, Bob Hanson wrote:
>
>> Java question: Does the following:
>>
>> for(i = 0; i < JpegObj.VsampFactor[comp]; i++) {
>> for(j = 0; j < JpegObj.HsampFactor[comp]; j++) {
>>
>>
>> benefit at all in performance with:
>>
>> int vsf = JpegObj.VsampFactor[comp];
>> int hsf = JpegObj.HsampFactor[comp];
>> for(i = 0; i < vsf; i++) {
>> for(j = 0; j < hsf; j++) {
>>
>>
>> Or does the Java compiler figure out that JpegObj.VsampFactor[comp] is
>> not changing during the loop and so only assigns it once?
>>
>>
>> Bob
>
>
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