Jim,
FYI, I am working on optimizing the 2 hotspot methods annotated by oprofile
(see specific emails) :
- ScanLineIterator.next() ~ 35%
- Renderer.endRendering(...) ~ 20%
I think that the ScanLineIterator class is no more useful and could be
merged into Renderer directly: I try to optimize these 2 code paths
(crossing / crossing -> alpha) but it seems quite difficult as I must
understand hotspot optimizations (assembler code)...
For now I want to keep pisces in Java code as hotspot is efficient enough
and probably the algorithm can be reworked a bit;
few questions:
- should edges be sorted by Ymax ONCE to avoid complete edges traversal to
count crossings for each Y value:
156 if ((bucketcount & 0x1) != 0) {
157 int newCount = 0;
158 for (int i = 0, ecur; i < count; i++) {
159 ecur = ptrs[i];* 160 if
(_edgesInt[ecur + YMAX] > cury) {* 161
ptrs[newCount++] = ecur;
162 }
163 }
164 count = newCount;
165 }
- why multiply x2 and divide /2 the crossings (+ rounding issues) ?
202 for (int i = 0, ecur, j; i < count; i++) {
203 ecur = ptrs[i];
204 curx = _edges[ecur /* + CURX */];
205 _edges[ecur /* + CURX */] = curx + _edges[ecur + SLOPE];
206 * 207 cross = ((int) curx) << 1;*
208 if (_edgesInt[ecur + OR] != 0 /* > 0 */) {
209 cross |= 1;
210 }
* 674 int lowx = crossings[0] >> 1;
675 int highx = crossings[numCrossings - 1] >> 1;*
689 for (int i = 0; i < numCrossings; i++) {
690 int curxo = crossings[i];* 691
int curx = curxo >> 1;*
- last x pixel processing: could you explain me ?
712 int pix_xmax = x1 >>
SUBPIXEL_LG_POSITIONS_X;
713 int tmp = (x0 & SUBPIXEL_MASK_X);
714 alpha[pix_x] += SUBPIXEL_POSITIONS_X - tmp;
715 alpha[pix_x + 1] += tmp;
716 tmp = (x1 & SUBPIXEL_MASK_X);
717 alpha[pix_xmax] -=
SUBPIXEL_POSITIONS_X - tmp;
718 alpha[pix_xmax + 1] -= tmp;
Finally, it seems that hotspot settings (CompileThreshold=1000 and
-XX:aggressiveopts) are able to compile theses hotspots better ...
2013/5/8 Jim Graham <james.gra...@oracle.com>
> This is amazing work, Laurent! I'll look over the code changes soon. Note
> that the "2 edge arrays" issue goes away if we can use native methods and C
> structs. It may be faster still in that case...
Thanks; probably the edgeBucket / edgeBucketCount arrays could be merged
into a single one to improve cache affinity.
Let stay in java ... as hotspot is so efficient (until the contrary is
proven).
FYI, I can write C/C++ code but I never practised JNI code.
Does somebody could help us to port only these 2 hotspot methods ?
PS: I attend a conference next week (germany) so I will be less available
to work on code but I will read my emails.
Laurent
