- Notifications
You must be signed in to change notification settings - Fork660
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.
By clicking “Sign up for GitHub”, you agree to ourterms of service andprivacy statement. We’ll occasionally send you account related emails.
Already on GitHub?Sign in to your account
Improve StringShrinker algorithm#377
Merged
Merged
Conversation
This file contains 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
The current string shrink algorithm generates candidates by dropping single characters from the end of the input. This doesn't produce the smallest case, since it doesn't drop characters from the start of the string. It is also linear on the size of the input, so it requires a potentially large number of tries to reach the result it does produce.This PR changes to algorithm to bisect the input string from both directions, producing a minimal output in log n tries.As an example of the current behavior, the test:`forAll { it: String -> !it.contains("#") }`produces output like this:```Attempting to shrink failed arg DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M#EC\M2yEcNn18+B*w,1x,L;6&k<}QQxU+!) e|Gr+ tri7jw{Shrink#1: <empty string> passShrink#2: DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M#EC\M2yEcNn18+B*w,1x,L;6&k<}QQxU+!) e|Gr+ tri7 failShrink#3: DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M#EC\M2yEcNn18+B*w,1x,L;6&k<}QQxU+!) e|Gr+ failShrink#4: DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M#EC\M2yEcNn18+B*w,1x,L;6&k<}QQxU+!) failShrink#5: DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M#EC\M2yEcNn18+B*w,1x,L;6&k<}QQx failShrink#6: DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M#EC\M2yEcNn18+B*w,1x,L;6&k failShrink#7: DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M#EC\M2yEcNn18+B*w,1x, failShrink#8: DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M#EC\M2yEcNn18+B* failShrink#9: DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M#EC\M2yEcNn failShrink#10: DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M#EC\M2 failShrink#11: DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M# failShrink#12: DPn CPQ7hBAY&LP;7MxPtN^Oy\$ passShrink#13: DPn CPQ7hBAY&LP;7MxPtN^Oy\$F passShrink#14: DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz passShrink#15: DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz; passShrink#16: DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M passShrink#17: aaaaaDPn CPQ7hBAY&LP;7MxPtN^Oy\$ passShrink#18: aaaaDPn CPQ7hBAY&LP;7MxPtN^Oy\$F passShrink#19: aaaDPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz passShrink#20: aaDPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz; passShrink#21: aDPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M passShrink result => DPn CPQ7hBAY&LP;7MxPtN^Oy\$Fz;M#```This is 21 attempts to produce a string 32x longer than optimal.The new algorithm produces output like this:```Attempting to shrink failed arg t ^j>t\o,x3?eb9#F'>g>vGQ-N}nkxShrink#1: <empty string> passShrink#2: t ^j>t\o,x3?eb9 passShrink#3: #F'>g>vGQ-N}nkx failShrink#4: #F'>g>vG failShrink#5: #F'> failShrink#6: #F failShrink#7: # failShrink result => #```This is only 7 tries, and produces the correct output of `"#"`Brilliant. |
Sign up for freeto join this conversation on GitHub. Already have an account?Sign in to comment
Labels
None yet
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
The current string shrink algorithm generates candidates by dropping single characters from the end of the input. This doesn't produce the smallest case, since it doesn't drop characters from the start of the string. It is also linear on the size of the input, so it requires a potentially large number of tries to reach the result it does produce.
This PR changes to algorithm to bisect the input string from both directions, producing a minimal output in log n tries.
As an example of the current behavior, the test:
forAll { it: String -> !it.contains("#") }produces output like this:
This is 21 attempts to produce a string 32x longer than optimal.
The new algorithm produces output like this:
This is only 7 tries, and produces the correct output of
"#"