Difference between revisions of "About CVC4"
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| − | The Cooperating Validity Checker series has a long history. The | + | The Cooperating Validity Checker series has a long history. The |
| − | Validity Checker | + | Stanford Validity Checker (SVC) came first in 1996, incorporating |
| − | its own SAT solver. | + | theories and its own SAT solver. Its successor, the Cooperating |
| − | Its successor, the Cooperating Validity Checker | + | Validity Checker (CVC), had a more optimized internal design, produced |
| − | had a more optimized internal design, produced proofs, used the | + | proofs, used the Chaff SAT solver, and featured a number of usability |
| − | Chaff | + | enhancements. Its name comes from the cooperative nature of decision |
| − | enhancements. Its name comes from the | + | procedures in Nelson-Oppen theory combination, which share amongst |
| − | decision procedures in Nelson-Oppen theory combination | + | each other equalities between shared terms. CVC Lite, first made |
| − | which share amongst each other equalities between shared terms. | + | available in 2003, was a rewrite of CVC that attempted to make CVC |
| − | CVC | + | more flexible (hence the "lite") while extending the feature set: CVC |
| − | that attempted to make CVC | + | Lite supported quantifiers where its predecessors did not. CVC3 was a |
| − | more flexible (hence the | + | major overhaul of portions of CVC Lite: it added better decision |
| − | + | procedure implementations, added support for using MiniSat in the | |
| − | CVC3 | + | core, and had generally better performance. |
| − | better decision procedure implementations, added support for using | + | |
| − | MiniSat | + | CVC4 is the new version, the fifth generation of this validity checker |
| + | line that is now celebrating sixteen years of heritage. It represents | ||
| + | a complete re-evaluation of the core architecture to be both | ||
| + | performant and to serve as a cutting-edge research vehicle for the | ||
| + | next several years. Rather than taking CVC3 and redesigning problem | ||
| + | parts, we've taken a clean-room approach, starting from scratch. | ||
| + | Before using any designs from CVC3, we have thoroughly scrutinized, | ||
| + | vetted, and updated them. Many parts of CVC4 bear only a superficial | ||
| + | resemblance, if any, to their correspondent in CVC3. | ||
| + | |||
| + | However, CVC4 is fundamentally similar to CVC3 and many other modern | ||
| + | SMT solvers: it is a DPLL(T) solver, with a SAT solver at its core and | ||
| + | a delegation path to different decision procedure implementations, | ||
| + | each in charge of solving formulas in some background theory. | ||
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The re-evaluation and ground-up rewrite was necessitated, we felt, by | The re-evaluation and ground-up rewrite was necessitated, we felt, by | ||
the performance characteristics of CVC3. CVC3 has many useful | the performance characteristics of CVC3. CVC3 has many useful | ||
| − | features, but some core aspects of the design led to high memory use, | + | features, but some core aspects of the design led to high memory use, |
| − | the use of heavyweight computation (where more nimble engineering | + | and the use of heavyweight computation (where more nimble engineering |
| − | approaches could suffice) makes CVC3 a much slower prover than other tools. | + | approaches could suffice) makes CVC3 a much slower prover than other |
| − | As these designs are central to CVC3, a new version was preferable to a | + | tools. As these designs are central to CVC3, a new version was |
| − | selective re-engineering, which would have ballooned in short order. | + | preferable to a selective re-engineering, which would have ballooned |
| − | Some specific deficiencies of CVC3 are mentioned in this article. | + | in short order. Some specific deficiencies of CVC3 are mentioned in |
| + | this article. | ||
Revision as of 09:52, 3 October 2012
The Cooperating Validity Checker series has a long history. The Stanford Validity Checker (SVC) came first in 1996, incorporating theories and its own SAT solver. Its successor, the Cooperating Validity Checker (CVC), had a more optimized internal design, produced proofs, used the Chaff SAT solver, and featured a number of usability enhancements. Its name comes from the cooperative nature of decision procedures in Nelson-Oppen theory combination, which share amongst each other equalities between shared terms. CVC Lite, first made available in 2003, was a rewrite of CVC that attempted to make CVC more flexible (hence the "lite") while extending the feature set: CVC Lite supported quantifiers where its predecessors did not. CVC3 was a major overhaul of portions of CVC Lite: it added better decision procedure implementations, added support for using MiniSat in the core, and had generally better performance.
CVC4 is the new version, the fifth generation of this validity checker line that is now celebrating sixteen years of heritage. It represents a complete re-evaluation of the core architecture to be both performant and to serve as a cutting-edge research vehicle for the next several years. Rather than taking CVC3 and redesigning problem parts, we've taken a clean-room approach, starting from scratch. Before using any designs from CVC3, we have thoroughly scrutinized, vetted, and updated them. Many parts of CVC4 bear only a superficial resemblance, if any, to their correspondent in CVC3.
However, CVC4 is fundamentally similar to CVC3 and many other modern SMT solvers: it is a DPLL(T) solver, with a SAT solver at its core and a delegation path to different decision procedure implementations, each in charge of solving formulas in some background theory.
The re-evaluation and ground-up rewrite was necessitated, we felt, by the performance characteristics of CVC3. CVC3 has many useful features, but some core aspects of the design led to high memory use, and the use of heavyweight computation (where more nimble engineering approaches could suffice) makes CVC3 a much slower prover than other tools. As these designs are central to CVC3, a new version was preferable to a selective re-engineering, which would have ballooned in short order. Some specific deficiencies of CVC3 are mentioned in this article.
