FazBrowse GitHub Viewer | Trending |
URL:
| Home
Tools: [Download Repo ZIP]   [Original HTTPS Page]

gh-115727: Reduce confidence even on 100% predicted jumps by gvanrossum · Pull Request #115748 · python/cpython · GitHub

/ cpython Public

gh-115727: Reduce confidence even on 100% predicted jumps #115748

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
gvanrossum merged 3 commits into from
Feb 22, 2024
Conversation 4 Commits 3 Checks 0 Files changed
Merged

gh-115727: Reduce confidence even on 100% predicted jumps #115748

Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
c1583b1
Improve debug logging for confidence
gvanrossum Feb 20, 2024
2537f75
Be less confident about jumps always/never taken
gvanrossum Feb 20, 2024
cdf96e2
Improve trace construction debug output
gvanrossum Feb 21, 2024
File filter

Filter by extension

Filter by extension .c  (1) All 1 file type selected
Viewed files
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Unified
Split
Hide whitespace
Diff view
Unified
Split
Hide whitespace
20 changes: 13 additions & 7 deletions Python/optimizer.c
Show comments
View file
Open in desktop
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
Show hidden characters
Original file line number Diff line number Diff line change
Expand Up @@ -546,6 +546,8 @@ translate_bytecode_to_trace(
uint32_t oparg = instr->op.arg;
uint32_t extended = 0;

DPRINTF(3, "%d: %s(%d)\n", target, _PyOpcode_OpName[opcode], oparg);

if (opcode == ENTER_EXECUTOR) {
assert(oparg < 256);
_PyExecutorObject *executor = code->co_executors->executors[oparg];
Expand Down Expand Up @@ -593,21 +595,25 @@ translate_bytecode_to_trace(
int counter = instr[1].cache;
int bitcount = _Py_popcount32(counter);
int jump_likely = bitcount > 8;
/* If bitcount is 8 (half the jumps were taken), adjust confidence by 50%.
If it's 16 or 0 (all or none were taken), adjust by 10%
(since the future is still somewhat uncertain).
For values in between, adjust proportionally. */
if (jump_likely) {
confidence = confidence * bitcount / 16;
confidence = confidence * (bitcount + 2) / 20;
}
else {
confidence = confidence * (16 - bitcount) / 16;
confidence = confidence * (18 - bitcount) / 20;
}
uint32_t uopcode = BRANCH_TO_GUARD[opcode - POP_JUMP_IF_FALSE][jump_likely];
DPRINTF(2, "%d: %s(%d): counter=%x, bitcount=%d, likely=%d, confidence=%d, uopcode=%s\n",
target, _PyOpcode_OpName[opcode], oparg,
counter, bitcount, jump_likely, confidence, _PyUOpName(uopcode));
if (confidence < CONFIDENCE_CUTOFF) {
DPRINTF(2, "Confidence too low (%d)\n", confidence);
DPRINTF(2, "Confidence too low (%d < %d)\n", confidence, CONFIDENCE_CUTOFF);
OPT_STAT_INC(low_confidence);
goto done;
}
uint32_t uopcode = BRANCH_TO_GUARD[opcode - POP_JUMP_IF_FALSE][jump_likely];
DPRINTF(2, "%s(%d): counter=%x, bitcount=%d, likely=%d, confidence=%d, uopcode=%s\n",
_PyOpcode_OpName[opcode], oparg,
counter, bitcount, jump_likely, confidence, _PyUOpName(uopcode));
_Py_CODEUNIT *next_instr = instr + 1 + _PyOpcode_Caches[_PyOpcode_Deopt[opcode]];
_Py_CODEUNIT *target_instr = next_instr + oparg;
if (jump_likely) {
Expand Down
Back | FazBrowse Home | New Git URL