Text_Diff_Engine_native::_compareseq( $xoff, $xlim, $yoff, $ylim )
- Source
wp-includes/Text/Diff/Engine/native.php:281
Description
The results are recorded in the vectors $this->{x,y}changed[], by storing a 1 in the element for each line that is an insertion or deletion (ie. is not in the LCS).
The subsequence of file 0 is (XOFF, XLIM) and likewise for file 1.
Note that XLIM, YLIM are exclusive bounds. All line numbers are origin-0 and discarded lines are not counted.
Compatibility
- WordPress
- core
- PHP
- 7.4–8.6-dev
- 6.7.7
- 6.8.8
- 6.9.7
- 7.0.4
- 7.1.0
Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.
Parameters
$xoff$xlim$yoff$ylim
Performance profile
How much work a call to Text_Diff_Engine_native::_compareseq() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.
- Cost class
- Light
- Scaling
- Scales with input
- Instructions
- 22–63
- Plugin surface
- None
- Called by
- 2
Touches nothing outside its own arguments.
The body loops, so the work grows with what you pass in.
Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 99.
Nothing here hands control to plugin code.
2 places in core call this, so the cost is paid more often than your own code shows.
What one call costs · 4 distinct outcomes
One number would be a lie: the work depends on which branch runs. These are every distinct cost Text_Diff_Engine_native::_compareseq() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
!$xoff && $lcs == 0 && !$yoff | 22–43 | none |
$lcs != 0 | 26–47 | reset(), next() |
!$xoff && $xoff != false && $yoff != false && $lcs == 0 && !$yoff | 40–59 | min(), ->_diag() |
$xoff != false && $yoff != false && $lcs != 0 | 44–63 | min(), ->_diag(), reset(), next() |
Across PHP versions
| PHP | Compiled | Executed | Branches | Notes |
|---|---|---|---|---|
| 8.6-dev | 99 | 22–63 | 12 | |
| 8.5 | 99 | 22–63 | 12 | |
| 8.4 | 99 | 22–63 | 12 | |
| 8.3 | 99 | 22–63 | 12 | |
| 8.2 | 99 | 22–63 | 12 | 1 more instruction than PHP 8.1 |
| 8.1 | 98 | 20–72 | 12 | 3 fewer instructions than PHP 7.4 |
| 7.4 | 101 | 20–82 | 12 |
An instruction is not a fixed amount of time, so a matching count is not necessarily the same speed; what it rules out is a difference in the work itself.
Uses · 2
- Text_Diff_Engine_native::_diag()Divides the Largest Common Subsequence (LCS) of the sequences (XOFF, XLIM) and (YOFF, YLIM) into NCHUNKS approximately equally sized segments.
- Text_Diff_Engine_native::_compareseq()Finds LCS of two sequences.
Used by · 2
- Text_Diff_Engine_native::_compareseq()Finds LCS of two sequences.
- Text_Diff_Engine_native::diff()
Source code
function _compareseq ($xoff, $xlim, $yoff, $ylim) { /* Slide down the bottom initial diagonal. */ while ($xoff < $xlim && $yoff < $ylim && $this->xv[$xoff] == $this->yv[$yoff]) { ++$xoff; ++$yoff; } /* Slide up the top initial diagonal. */ while ($xlim > $xoff && $ylim > $yoff && $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) { --$xlim; --$ylim; } if ($xoff == $xlim || $yoff == $ylim) { $lcs = 0; } else { /* This is ad hoc but seems to work well. $nchunks = * sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5); $nchunks = * max(2,min(8,(int)$nchunks)); */ $nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1; list($lcs, $seps) = $this->_diag($xoff, $xlim, $yoff, $ylim, $nchunks); } if ($lcs == 0) { /* X and Y sequences have no common subsequence: mark all * changed. */ while ($yoff < $ylim) { $this->ychanged[$this->yind[$yoff++]] = 1; } while ($xoff < $xlim) { $this->xchanged[$this->xind[$xoff++]] = 1; } } else { /* Use the partitions to split this problem into subproblems. */ reset($seps); $pt1 = $seps[0]; while ($pt2 = next($seps)) { $this->_compareseq ($pt1[0], $pt2[0], $pt1[1], $pt2[1]); $pt1 = $pt2; } } }Changelog
Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
About this page
- Parsed data
- Generated from the wordpress-develop 7.1.0 tag, from
src/wp-includes/Text/Diff/Engine/native.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it. - Corrections
- Something wrong on this page? Report it and it gets fixed in the next regeneration.