Advanced Line-Pairing Preferences

The controls on this sheet enable advanced line-pairing preferences to be adjusted. The default settings should be suitable for most users and most files. Please see the entire Pairing topic for further information about line-pairing.

How much computational effort should be expended to pair lines in changes containing large numbers of similar (but not identical) lines?

Move this slider further to the right if your files tend to have very large blocks of changed text and Merge is not acceptably pairing lines within those large blocks. Move the slider further to the left if comparison performance is unacceptably slow for files containing very large change-blocks.

Discussion

The computational effort required to find the best pairings between lines in a large block of changed text can be considered to be roughly proportional to the product of the number of lines on the left and right sides of the block. For very complex change-blocks (e.g. those consisting of thousands of lines on both the left and right), the effort required to compute optimal line-pairings can be considerable, and the performance of text comparisons can therefore be impaired.

This slider adjusts the threshold of change-block complexity above which Merge will no longer seek to determine optimal line-pairings between the left and right sides of the block. Optimal line-pairings will be found for change-blocks of lower complexity than the threshold. For change-blocks above the threshold, Merge will use a more efficient algorithm that will endeavour to produce appropriate line pairings. These can often be the same as the optimal line pairings, but are not guaranteed to be so. A balance may therefore be struck between comparison performance and the complexity of change-blocks for which optimal line-pairings are guaranteed to be found.

How similar must a pair of lines be for them to be highlighted as a change (rather than as a removal and an insertion)?

Move this slider leftwards if you wish Merge to highlight more pairs of lines in change-blocks as having been changed, rather than as representing a removal of the left line in the pair and an insertion of the right line. Move the slider rightwards to highlight fewer pairs of lines as having been changed, and more as representing a removal and an insertion.

Information Moving the slider all the way to the left will mean that all paired lines will be highlighted as having been changed, unless they are completely different. Moving the slider all the way to the right will result in all paired lines being highlighted as representing a removal and an insertion.

Discussion

Once lines within a block of changed text have been paired, Merge needs to decide how to highlight them. If the line on the left of a pair is sufficiently different from the line on the right, Merge will highlight the left line as a removal, and the right line as an insertion. If the two lines are sufficiently similar, Merge will highlight both lines as having been changed (because the right line is a modified form of the left), and then further proceed to highlight differences in the text content of the lines, according to the setting of the Show detailed (rather than simple) inline changes within paired lines preference on the Pairing preferences page.

This slider determines the threshold at which lines are considered sufficiently similar when deciding whether the the right line in a pair is a modified form of the left line (resulting in the lines being highlighted as a change), or otherwise that left and right lines in a pair are unrelated (thus resulting in the lines being highlighted as representing a removal and an insertion).

When the slider has its default, centre position, a pair of lines will be highlighted as a removal and an insertion if more characters within the lines have changed than have stayed the same. Otherwise, if more characters have stayed the same than have changed, the lines will be highlighted as having been changed, since the right line appears to be a modified form of the left.

When the slider is moved towards the left, Merge uses a lower threshold for determining that lines are sufficiently similar so as to be considered related, and should thus be highlighted as a change. As the slider is moved further left, fewer characters need to have remained unchanged between the left and right lines in a pair for those lines still to be considered related.

When the slider is moved towards the right, Merge uses a higher threshold for determining that lines are sufficiently similar so as to be considered related. As the slider is moved further right, more characters need to have remained unchanged between the left and right lines in a pair for those lines to be considered related.

Reset to Defaults

This button sets the above two sliders to their default values; the defaults should work well for most files.