Tag Archives: Release

CryptoMiniSat 2.9.0 released

SAT,

After a long break, CryptoMiniSat 2.9.0 has finally been released. The Windows executables need this to work, and the Linux binaries need a recent (>=2.6.26) kernel version. The program has evolved substantially since the last release — more than half of its codebase has been changed. It now works in multi-threaded mode, and uses lazy cached implications for all sorts of interesting purposes from simple transitive on-the-fly self-subsuming resolution to very efficient literal dependency analysis. Currently, the program solves ~225 problems from the 2009 SAT Competition examples given the same time and similar computing power. This is a nice improvement over other SAT solvers such as MiniSat (205), PrecoSat (210) or lingeling (207).

Intensive testing has been carried out on this version of the program, to the extent of finding and identifying a new and unknown gcc bug affecting all gcc versions 4.5.0 and later. Many have played part in finding this and other bugs, including, but not limited to, Martin Maurer, Vegard Nossum, Oliver Kullmann, Robert Aston, and others. This release has been made possible thanks to them.

I hope this version of the code will be useful to many, not only end users but also researchers. In fact I decided to release this version (relatively) early to let researchers merge their changes for the upcoming SAT Competition 2011. I am very interested in any and all versions of CryptoMiniSat that will be submitted to the competition. In case you personally want to change it and find something difficult to understand, just drop a mail to the nowadays very active development mailing list. With this release, I can confidently say that CryptoMiniSat is becoming not only a programming project but also a community. If you feel like you could contribute, or you are simply interested in what is going on, join us.

As for the technical details, the new CryptoMiniSat uses OpenMP for mutli-threading which means it is fully platform-independent. During multi-threading we share unitary and binary clauses between threads — the latter is checked for redundancy using lazy cached implications. We use implicit binary clauses, which don’t help as much in terms of memory as I have hoped, but they help immensely for certain operations, in particular with subsumption checks. Literal dependencies are now calculated using the lazy cached implications and the dominating literal with the largest tree is selected as dominant literal for all literals: when picking variables, we pick the dominating literal 50% of the time instead of the original literal. Variable elimination heuristics have also been highly tuned thanks to the much better at-hand statistics due to implicit binary clauses.

Unfortunately, this version doesn’t offer all the things I wanted it to offer: multi-threaded library interface, extended resolution, distributed solving through MPI, unified restart strategy, and others. All of these (except MPI), and more are however available from the public GIT repository. They work relatively stable, but have a terrible speed: the version with all of these only solves ~214 problems from those above. Therefore, I will personally submit version 2.9.0 to the SAT Competition unless some grave bug is found inside. I might also submit a corrected version of the upcoming 3.0.0 release as well, but as it usually takes a month to tune the solver, and I am currently very busy with some great projects at my new workplace, so a 3.0.0 version probably won’t happen until the deadline.

I hope you will enjoy this new version of CryptoMiniSat! In case of questions, problems or bugs, please contact either me, or the development mailing list and join in to collaborate :)

CryptoMiniSat 2.7.1 released

SAT

It has been a long and winding road, but finally, CryptoMiniSat 2.7.1 has been released. The main additions relative to version 2.6.0 are:

  • Lots of documentation. I have added ~1’500 lines of comments to aid developers and user alike
  • Transitive on-the-fly self-subsuming resolution — an optimisation I have blogged about
  • Memory allocator has been fixed and updated
  • DIMACS parsing is now much better, which should allow for very interesting usage scenarios

Although the above list doesn’t seem to talk about performance, let me talk about it first. My personal point of view on performance is that different applications have different needs, so even if overall some solver is the best, it might not mean that it is the best for a particular application. I compared the performance of CryptoMiniSat 2.7.1 to the other mainline solvers, namely MiniSat 2.2, PrecoSat465, and lingeling. I ran the problem instances of the 2009 SAT Competition, with a timeout of 6’000 seconds on some powerful computers. The results are the following:

CryptoMiniSat could solve 225 problem instances (223 within SATComp’09 limits), and the second best solver, lingeling, could solve 211 (207 within SATComp’09 limits). Interestingly, both MiniSat 2.2 and lingeling were better than CryptoMiniSat 2.7.1 at low timeouts, and lingeling kept this advantage the longest, until ~500 seconds, above which CryptoMiniSat took over. Not being too fast at the beginning is a conscious choice by me, as I think it helps in the long run, though I might be wrong. There is much to be improved, and I hope that the immense amount of documentation added will help those willing to try to iron out these shortcomings.

As for the DIMACS parsing update, it basically allows to add information to clauses to distinguish between learnt and non-learnt clauses. This helps, because it is now possible to simply dump the learnt clauses at any moment during the search, and then re-start the search more-or-less where it was stopped. The command-line options for this are “–dumplearnts=FILENAME –maxdumplearnts=3” to dump, and “–alsoread=FILENAME” to re-read. This is currently quite a crude way of stopping-and-starting, but hopefully it will improve in the future.

All in all, I am quite happy about the new release. I have put lots of time into it, and I hope you will enjoy using it :)

CryptoMiniSat 2.6.0 released

SAT, ,

Version 2.6.0 of the CryptoMiniSat SAT solver has been released. The new release incorporates a number of important additions and discoveries. Additions include a better memory manager and better watchlists, while the discoveries include an interesting use of asymmetric branching and an on-the-fly self-subsuming resolution algorithm.

The new solver can now solve 221 problems from the SAT Competition of 2009 within the same timing&CPU constraints, while the 2.5.0 (i.e. SAT Race) version could only solve 217. Here is a comparison plot:

The cut-off for the competition for these machines was approx at 5000 sec. As can be seen from the graph (which goes until 6000 sec), the new solver does even better in the longer run:  the additions seem to improve the long-term behaviour.

As for the future, I think there is still a lot of things to do. For example, the solver still doesn’t have blocked clause elimination, which could help, and it is still missing some ideas that others have published. Notably, it doesn’t do on-the-fly subsumption at every step of the conflict generation process, only at the very last step. In case you are interested to add any of these in a transparent manner, feel free to hack away at the git repository.

Edited to Add (3/09/2010): The performance of CryptoMiniSat on the SAT Race 2010 problems has also changed with the new version. The new CryptoMiniSat can now solve 75 problems (instead of 74) within the time limit. More importantly, the average time to solve these 75 instances has decreased considerably, to around 111 seconds per instance (from 138 s/inst), which is very close to the results of lingeling, an extremely fast and very advanced solver. There is still a lot to be learnt from lingeling, however: its memory footprint is far smaller, and its preprocessing techniques in some areas are much better than that of CryptoMiniSat.

The Obvious Child

SAT, ,

The new CryptoMiniSat 2.5.1, codenamed “The Obvious Child” has been released. It’s very close to the system that has been sent into the SAT Race’10. This version of CryptoMS is much better than any versions before: I finally corrected a lot of bugs that went into the 2.4.x series, and added new features to treat binary clauses.

The release name is the song title by Paul Simon. I am a fan of the 60’s for many reasons. It was the time when Laing wrote his first books, empathy was first scientifically demonstrated for animals, the days of I have a dream, the landing on the moon, and the take-off of Simon&Garfunkel.; Some interesting times, shall we say.

I probably will be working less on CryptoMiniSat from now on, instead concentrating on other things that I must do, such as publishing research papers on subjects that interest the scientific community. I will also be trying to play out in my mind how CryptoMiniSat will fare in the SAT Race. Of course I am hoping for the best, but I worked on the program for a mere 8 months, alone. Comparing this to some experts working on their solvers for multiple years in groups of 2-3, I really have no chance of winning. However, I am optimistic, as always: maybe I will get some good position in the rankings :)

Gaussian elimination is released

SAT, ,

The new CryptoMiniSat, version 2.4.2 now has on-the-fly Gaussian elimination compiled in by default. You can simply use it by issuing e.g.

./cryptominisat --gaussuntil=100 trivium-cipher.cnf

and enjoy outputs such as:

c gauss unit truths : 0
c gauss called : 31323
c gauss conflicts : 5893 (18.81 %)
c gauss propagations : 7823 (24.98 %)
c gauss useful : 43.79 %
c conflicts : 34186 (4073.39 / sec)
c decisions : 39715 (6.86 % random)

Which basically tells that gaussian elimination was called 31 thousand times out of 39 thousand, and so it was essentially running almost all the time. Out of the 31’323 times it was called, 44% of the cases it found either a conflict or a propagation. This is a very good result, and is typical of the Trivium cipher. Trivium can be speeded up by up to 2x with Gaussian elimination. I will put up lots of CNFs, so you will be able to play around with them and (optionally) verify these results.

The magic parameter “–gaussuntil=100” tells the program to execute Gaussian elimination until decision level 100, and no deeper. I haven’t implemented and automation into finding the best depth, and so I use this (very) crude fixed number 100. Probably better results could be achieved with a fine tuning of the depth cut-off, but I don’t have the time for the moment to play around with it. However, if you are interested, you will be able to try out different depths, different ciphers, etc. I will shortly be releasing a tool called “Grain of Salt” to generate CNFs for any shift-register based stream cipher, so you can test them against CryptoMiniSat or any other SAT solver.

I hope you will enjoy using on-the-fly Gaussian elimination in CryptoMiniSat 2.4.2!