Question

I’m currently using the Alloy Analyzer API to build a program, and getting some peculiar behavior. Specifically, if I open a file and parse it (using CompUtil.parseEverything), then make a new Command and call TranslateAlloyToKodkod.execute_command on the parsed file and newly created command using MiniSat with UNSAT core, it runs fine. However, later in execution, my program parses a second input file (also using CompUtil.parseEverything), gets another world, makes a new command, and then I try to call TranslateAlloyToKodkod.execute_command again, it throws the following error:

ERROR: class edu.mit.csail.sdg.alloy4.ErrorFatal: The required JNI library cannot be found:
java.lang.UnsatisfiedLinkError: no minisatproverx5 in java.library.path
edu.mit.csail.sdg.alloy4compiler.translator.TranslateAlloyToKodkod.execute_command(TranslateAlloyToKodkod.java:390)

Does anyone have any idea why this is thrown the second time, but not the first?

To summarize, I have something similar to the following:

Module someWorld = CompUtil.parseEverything_fromFile(rep, null, "someFile.als");
//For the following, "sig" is a sig in someWorld.getAllReachableSigs();
Command command = sig.not();
A4Options options = new A4Options();
options.solver = A4Options.SatSolver.MiniSatProverJNI;
A4Solution ans = 
    TranslateAlloyToKodkod.execute_command(rep, someWorld, command, options);
//No thrown error
Module someOtherWorld = CompUtil.parseEverything_fromFile(rep, null, "someOtherFile.als");
//For the following, "sig" is a sig in someOtherWorld.getAllReachableSigs();
Command commandTwo = sig.not();
A4Solution ansTwo = 
    TranslateAlloyToKodkod.execute_command(rep, someOtherWorld, commandTwo, options);
//Thrown error above. Why?

Answer 1

I tried to reproduce this behavior, but I couldn’t. If I don’t add MiniSat binaries to the LD_LIBRARY_PATH environment variable, I get the exception you mentioned the very first time I invoke execute_command. After configuring LD_LIBRARY_PATH, the exception doesn’t happen.

To configure LD_LIBRARY_PATH:

(1) if using Eclipse, you can right-click on one of your source folders, choose Build Path -> Configure Build Path, then on the "Source" tab make sure that "Native library location" points to a folder in which MiniSat binaries reside.

(2) if running from the shell, just add the path to a folder with MiniSat binaries to LD_LIBRARY_PATH, e.g., something like export LD_LIBRARY_PATH=alloy/extra/x86-linux:$LD_LIBRARY_PATH.

Here is the exact code that I was running, and everything worked

public static void main(String[] args) throws Exception {
    A4Reporter rep = new A4Reporter();

    A4Options options = new A4Options();
    options.solver = A4Options.SatSolver.MiniSatProverJNI;
    
    Module someWorld = CompUtil.parseEverything_fromFile(rep, null, "someFile.als");
    Command command = someWorld.getAllCommands().get(0);
    A4Solution ans = TranslateAlloyToKodkod.execute_command(rep, someWorld.getAllReachableSigs(), command, options);
    System.out.println(ans);
    
    Module someOtherWorld = CompUtil.parseEverything_fromFile(rep, null, "someOtherFile.als");
    Command commandTwo = someOtherWorld.getAllCommands().get(0);
    A4Solution ansTwo = TranslateAlloyToKodkod.execute_command(rep, someOtherWorld.getAllReachableSigs(), commandTwo, options);
    System.out.println(ansTwo);
}

with "someFile.als" being

sig A {}
run { some A } for 4

and "someOtherFile.als"

sig A {}
run { no A } for 4