Merge branch 'certification'

- Support for post-hoc certification via three targets---HTT, VST,
  Iris.
- More uniform/traversable representation of the source "ProofTree"
  used in certification, which contains a tree of successful
  derivations, with each node encoded as a "SuslikProofStep".
- A script (CertificationBenchmarks.scala) to evaluate characteristic
  test cases.

.gitignore

@@ -147,4 +147,8 @@ node_modules
 
 # traces
 *.out
+
+# certification results
+certify/
+
 *results.tex

README.md

@@ -22,6 +22,9 @@ The details of Synthetic Separation Logic and its extensions can be found in the
 * **[Cyclic Program Synthesis](https://doi.org/10.1145/3453483.3454087)**  
   Shachar Itzhaky, Hila Peleg, Nadia Polikarpova, Reuben Rowe, and Ilya Sergey. PLDI'21
   - [Artifact, 11 Apr 2021](https://doi.org/10.5281/zenodo.4679743)
+* **[Certifying the Synthesis of Heap-Manipulating Programs](https://doi.org/10.1145/3473589)**
+  Yasunari Watanabe, Kiran Gopinathan, George Pîrlea, Nadia Polikarpova, and Ilya Sergey. ICFP'21
+  - [Artifact, 21 May 2021](http://doi.org/10.5281/zenodo.5005829)
 
 ## Benchmark Statistics
 
@@ -178,10 +181,10 @@ where the necessary arguments and options are
                            dump entire proof search trace to a json file; default: none
   --memo <value>           enable memoization; default: true
   --lexi <value>           use lexicographic termination metric (as opposed to total size); default: false
-  --printTree <value>      print tree of successful derivations to path; default: false
-  --treeDest <value>       write tree of successful derivations to path; default: none
-  --certTarget <value>     set certification target; default: none
-  --certDest <value>       write certificate to path; default: none
+  --certTarget <value>           set certification target; default: none (options: htt | vst | iris)
+  --certDest <value>             specify the directory in which to store the certificate file; default: none
+  --certHammerPure <value>       use hammer to solve pure lemmas instead of admitting them (HTT only); default: false
+  --certSetRepr <value>          use SSReflect's perm_eq to represent set equality (HTT only); default: false
   --help                   prints this usage text
 
 ```
@@ -217,4 +220,8 @@ void listcopy (loc r) {
 For running advanced examples from the accompanying test suite, execute, e.g.,
 ```
 ./suslik src/test/resources/synthesis/all-benchmarks/sll/append.syn
-``` 
+``` 
+
+## Certification
+
+Please refer to `certification.md` for information on certifying the synthesis results.

build.sbt

@@ -5,7 +5,7 @@ name := "suslik"
 
 version := "0.1.0"
 
-scalaVersion := "2.12.7"
+scalaVersion := "2.12.12"
 
 javacOptions ++= Seq("-source", "1.8", "-target", "1.8", "-Xlint")
 scalacOptions += "-target:jvm-1.8"
@@ -54,4 +54,4 @@ assemblyJarName in assembly := "suslik.jar"
 assemblyMergeStrategy in assembly := {
  case PathList("META-INF", xs @ _*) => MergeStrategy.discard
  case x => MergeStrategy.first
-}
+}

certification.md

@@ -1,34 +1,227 @@
-# Certified Synthesis
+# Certifying Synthesis Results
 
-Generation of correctness certificates for synthesized programs. Currently, we support Coq as the certification backend.
+This page contains instructions for running and evaluating the certification component of SuSLik, corresponding to the
+following paper.
 
-## Coq
+**[Certifying the Synthesis of Heap-Manipulating Programs](https://doi.org/10.1145/3473589)**  
+  Yasunari Watanabe, Kiran Gopinathan, George Pîrlea, Nadia Polikarpova, and Ilya Sergey. ICFP'21
+  - [Artifact, 21 May 2021](http://doi.org/10.5281/zenodo.5005829)
 
-### Requirements
+Currently, we support three target verification frameworks in Coq—HTT, VST, and Iris—to generate correctness
+certificates for synthesized programs.
 
-- [Coq](https://coq.inria.fr/) (>= "8.9.0" & < "8.12~")
-- [Mathematical Components](http://math-comp.github.io/math-comp/) `ssreflect` (>= "1.10.0" & < "1.11~")
-- [FCSL PCM library](https://github.com/imdea-software/fcsl-pcm) (>= "1.0.0" & < "1.3~")
-- [HTT](https://github.com/TyGuS/htt)
+## Requirements
 
-### Building Definitions and Proofs
+Follow the instructions in the README of each repository below to install the necessary
+Coq libraries. Each repository also has a `benchmarks/` directory where examples of generated
+certificates are viewable.
 
-For Coq requirements available on [OPAM](https://opam.ocaml.org/doc/Install.html), we recommend installing with it:
+- HTT ([`TyGuS/ssl-htt`](https://github.com/TyGuS/ssl-htt))
+- VST ([`TyGuS/ssl-vst`](https://github.com/TyGuS/ssl-vst))
+- Iris ([`TyGuS/ssl-iris`](https://github.com/TyGuS/ssl-iris))
 
+## Synthesis with Certification
+
+Add the following flags to run synthesis with certification.
+
+- `--certTarget <value>`: Currently supports values `htt`, `vst`, `iris`.
+- `--certDest <value>` (optional): Specifies the directory in which to generate a certificate file. Logs output to console if not provided.
+
+For example, the following command produces a HTT certificate of the specification `listfree.syn`, and logs its contents to the console.
+
+```bash
+./suslik examples/listfree.syn --assert false --certTarget htt
 ```
-opam repo add coq-released https://coq.inria.fr/opam/released
-opam pin add coq-htt git+https://github.com/TyGuS/htt\#master --no-action --yes
-opam install coq coq-mathcomp-ssreflect coq-fcsl-pcm coq-htt
+
+By providing the `--certDest` flag, SuSLik writes out this certificate as a file to the specified directory. The following example command writes a HTT certificate named `listfree.v` to the project root directory.
+
+```bash
+./suslik examples/listfree.syn --assert false --certTarget htt --certDest .
 ```
 
-Each synthesized Coq certificate imports `SSL`, a module consisting of predefined tactics. The module source may be compiled by running `make clean && make` in the directory `certification/coq`.
+### Optional Flags
 
-### Running Synthesis with Certification
+If HTT is chosen as the certification target, you can control additional certification parameters.
+Note that this has no effect if Iris or VST are chosen.
 
-Add the following flags to run synthesis with certification.
+- `--certHammerPure <value>` (boolean; default is `false`):
+Controls whether to use CoqHammer to solve pure lemmas.
+If `false`, the generated certificate will have all pure lemmas `Admitted` instead.
+- `--certSetRepr <value>` (boolean; default is `false`):
+Controls whether to use SSReflect's `perm_eq` to express multi-set equality.
+If `false`, the generated certificate will use regular equality (`=`) instead.
 
-- `--certTarget <value>`: Currently supports value `coq`.
-- `--certDest <value>` (optional): Specifies the directory in which to generate a certificate file. Logs output to console if not provided.
+## Evaluation
+
+### Overview
+
+The paper discusses two classes of benchmarks.
+
+1. **Standard benchmarks** are supported by HTT, VST, and Iris. This
+   corresponds to Table 1 of the paper. These are available in the folder
+   `$SUSLIK_ROOT/src/test/resources/synthesis/certification-benchmarks`.
+2. **Advanced benchmarks** are supported by HTT only. These include test
+   cases that use an alternative representation of multi-set equality and
+   requires manual editing of pure lemma proofs. This corresponds to
+   Table 2 of the paper. These are available in the folder
+   `$SUSLIK_ROOT/src/test/resources/synthesis/certification-benchmarks-advanced`
+
+The tool `certify-benchmarks` synthesizes proof certificates for
+  both standard and advanced benchmarks, and compiles the certificates for
+  standard benchmarks only.
+
+The [`ssl-htt`](https://github.com/TyGuS/ssl-htt) repository contains a benchmarking script to compile the HTT
+certificates for advanced benchmarks.
+
+### Generating All Certificates and Compiling Standard Benchmarks
+
+To synthesize standard and advanced benchmark certificates, and compile
+the standard benchmark certificates, execute:
+
+```
+cd $SUSLIK_ROOT
+./certify-benchmarks
+```
+
+This will run SuSLik with certificate generation flags enabled, for all
+specification (`.syn`) files in the standard and advanced benchmarks,
+for all three target frameworks.
+Then, for the standard benchmarks, it will also compile the generated
+certificates.
+These are the default evaluation configuration, and the exact actions that will
+be performed under this configuration are written to timestamped `.log` files in
+the `certify` directory before each run. This configuration can be modified
+by setting the `--configure` flag. See section "Customizing Benchmark Options"
+for details.
+
+As this script produces verbose output, you may consider teeing the script's
+output to a log file for viewing/debugging later, instead of running the script
+directly.
+
+```
+./certify-benchmarks> >(tee certify.log)
+cat certify.log
+```
+
+When running the tool, please keep in mind the following.
+
+- **It should take _2-3 hours_ to run this evaluation on all benchmark
+  groups and all target frameworks.** If you need to interrupt the evaluation,
+  or if the benchmarking encounters a timeout error on a slow machine, please
+  refer to section "Customizing Benchmark Options" on how to resume the task
+  with selected benchmark groups/target frameworks only.
+- **Files in the `certify` directory will be overwritten on each subsequent
+  run.**
+- Unsupported test cases for certain targets (such as `sll_max` for Iris,
+  as indicated in Table 1) are ignored.
+- Warnings displayed during the proofs do not affect the functionality of the
+  certificates.
+
+After the script terminates, it will create five output files in
+`$SUSLIK_ROOT/certify`.
+
+- `standard-syn.csv` contains synthesis times reported in Table 1.
+- `standard-{HTT,VST,Iris}.csv` contain proof/spec size and compilation
+  times for each of the three target frameworks in Table 1.
+- `advanced-syn.csv` contains synthesis times reported in Table 2.
+
+#### Customizing Benchmark Options
+
+You may wish to run the benchmarks with alternative settings.
+
+To produce certificates and stats CSV files in a directory other than
+`$SUSLIK_ROOT/certify`, run the tool with the `--outputDir` flag.
+
+```
+cd $SUSLIK_ROOT
+./certify-benchmarks --outputDir <ALTERNATIVE_DIR_PATH>
+```
+
+As the benchmark tool takes several hours to run, you may need to interrupt
+its execution, and then resume later on a subset of the benchmarks/frameworks.
+If so, you can run the tool with the `--configure` flag.
+
+```
+cd $SUSLIK_ROOT
+./certify-benchmarks --configure
+```
+
+When this flag is set, a configuration wizard is run before the benchmarks,
+where you can selectively enable/disable three benchmarking parameters.
+
+- **Compilation:** Choose whether to measure compilation times of the
+  generated certificates or not.
+- **Benchmark groups:** Select which benchmark groups to evaluate.
+- **Target frameworks:** Select which target framework to generate/compile
+  certificates for.
+
+At each prompt, press ENTER to select the default option; alternatively, choose
+the desired option (`y` or `n`). The default settings are:
+
+- _For standard benchmarks_: Synthesize programs in all benchmark groups. Then
+  generate and compile certificates for all three targets (HTT/VST/Iris).
+- _For advanced benchmarks_: Synthesize programs in all benchmark groups. Then
+  generate (but _don't_ compile) certificates for HTT only.
+
+Each execution of the script generates a timestamped `.log` file listing
+exactly what actions will be performed given the user-specified configuration,
+which may be useful for debugging.
+
+### Compiling Advanced Benchmarks (Manually Edited Proofs)
+
+The steps from the above section do not produce target-specific statistics for
+advanced benchmarks. This is because the test cases in Table 2 require manual
+editing of the pure lemma proofs (as discussed in Section 8.2 of the paper),
+whereas that tool only checks SuSLik-generated certificates.
+
+To compile the advanced benchmark certificates with manually edited pure lemma
+proofs and execute the following (`$SSL_HTT_ROOT` refers to the local `ssl-htt` repository).
+
+```
+cd $SSL_HTT_ROOT/benchmarks/advanced
+python3 benchmark.py --diffSource $SUSLIK_ROOT/certify/HTT/certification-benchmarks-advanced
+```
+
+**It should take roughly _10 minutes_ to run this evaluation**.
+
+After the script terminates, it will create two output files in
+`$SSL_HTT_ROOT/benchmarks/advanced`.
+
+- `advanced-HTT.csv` contains proof/spec size and compilation times for HTT
+  in Table 2.
+- `advanced-HTT.diff` compares the original SuSLik-generated certificates
+  (stored in
+  `$SUSLIK_ROOT/certify/HTT/certification-benchmarks-advanced`) with the
+  manually edited ones (stored in `$SSL_HTT_ROOT/benchmarks/advanced`),
+  showing which lines have been modified. The diff file will only be created if
+  the original SuSLik-generated certificates exist.
+
+The number of pure lemmas and those with manual proofs can be verified by
+inspecting the files at `$SSL_HTT_ROOT/benchmarks/advanced`.
+You can also view the diff file to verify which parts of the proofs have been
+edited.
+
+```
+less advanced-HTT.diff
+```
+
+You can expect to see the following differences between the two proof versions.
 
+- _Proofs for the pure lemmas:_ In the generated scripts, pure lemmas have
+  their `hammer` proofs replaced with `Admitted` statements. In the manually
+  edited scripts, these are replaced with either a call to `hammer` when that is
+  sufficient, or with a proof manually constructed by the authors. Note that in
+  the diff file, pure lemmas may be ordered differently between the two
+  versions, due to non-determinism in the way Scala accumulates hints during
+  execution.
+- _Administrative renaming statements in the main proof:_ These are
+  identifiable by the `try rename ...` statements; they may occur when
+  two variable rename statements resulting from the same proof step
+  are applied in different orders between the compared proofs, again
+  dependent on Scala's execution.
 
+You should _not_ see edits that modify the main proof structure (aside from
+renaming variables).
 
+To use this tool with custom settings, execute the script with the `--help` flag to see all
+available options.