Overflow when using RandomSubset

TLC encounters an overflow error when evaluating the RandomSubset operator from the Randomization module with with a record set that is too big. For example, evaluating the following in the TLC REPL:

(tla+) RandomSubset(3, SUBSET [a:1..8, b:1..8])
util.Assert$TLCRuntimeException: Attempted to apply the operator overridden by the Java method
public static tlc2.value.impl.Value tlc2.module.Randomization.RandomSubset(tlc2.value.impl.Value,tlc2.value.impl.Value),
but it produced the following error:
Overflow when computing the number of elements in:
SUBSET { [a |-> 1, b |-> 1],
   [a |-> 1, b |-> 2],
   [a |-> 1, b |-> 3],
   [a |-> 1, b |-> 4],
   [a |-> 1, b |-> 5],
   [a |-> 1, b |-> 6],
   [a |-> 1, b |-> 7],
   [a |-> 1, b |-> 8],
   [a |-> 2, b |-> 1],
   [a |-> 2, b |-> 2],
   [a |-> 2, b |-> 3],
   [a |-> 2, b |-> 4],
   [a |-> 2, b |-> 5],
   [a |-> 2, b |-> 6],
   [a |-> 2, b |-> 7],
   [a |-> 2, b |-> 8],
   [a |-> 3, b |-> 1],
   [a |-> 3, b |-> 2],
   [a |-> 3, b |-> 3],
   [a |-> 3, b |-> 4],
   [a |-> 3, b |-> 5],
   [a |-> 3, b |-> 6],
   [a |-> 3, b |-> 7],
   [a |-> 3, b |-> 8],
   [a |-> 4, b |-> 1],
   [a |-> 4, b |-> 2],
   [a |-> 4, b |-> 3],
   [a |-> 4, b |-> 4],
   [a |-> 4, b |-> 5],
   [a |-> 4, b |-> 6],
   [a |-> 4, b |-> 7],
   [a |-> 4, b |-> 8],
   [a |-> 5, b |-> 1],
   [a |-> 5, b |-> 2],
   [a |-> 5, b |-> 3],
   [a |-> 5, b |-> 4],
   [a |-> 5, b |-> 5],
   [a |-> 5, b |-> 6],
   [a |-> 5, b |-> 7],
   [a |-> 5, b |-> 8],
   [a |-> 6, b |-> 1],
   [a |-> 6, b |-> 2],
   [a |-> 6, b |-> 3],
   [a |-> 6, b |-> 4],
   [a |-> 6, b |-> 5],
   [a |-> 6, b |-> 6],
   [a |-> 6, b |-> 7],
   [a |-> 6, b |-> 8],
   [a |-> 7, b |-> 1],
   [a |-> 7, b |-> 2],
   [a |-> 7, b |-> 3],
   [a |-> 7, b |-> 4],
   [a |-> 7, b |-> 5],
   [a |-> 7, b |-> 6],
   [a |-> 7, b |-> 7],
   [a |-> 7, b |-> 8],
   [a |-> 8, b |-> 1],
   [a |-> 8, b |-> 2],
   [a |-> 8, b |-> 3],
   [a |-> 8, b |-> 4],
   [a |-> 8, b |-> 5],
   [a |-> 8, b |-> 6],
   [a |-> 8, b |-> 7],
   [a |-> 8, b |-> 8] }
	at util.Assert.fail(Assert.java:33)
	at tlc2.value.impl.MethodValue.apply(MethodValue.java:176)
	at tlc2.value.impl.OpValue.eval(OpValue.java:25)
	at tlc2.tool.impl.Tool.evalApplImpl(Tool.java:1706)
	at tlc2.tool.impl.FastTool.evalAppl(FastTool.java:98)
	at tlc2.tool.impl.Tool.evalImpl(Tool.java:1468)
	at tlc2.tool.impl.FastTool.eval(FastTool.java:91)
	at tlc2.tool.impl.Tool.eval(Tool.java:1364)
	at tlc2.REPL.processInput(REPL.java:121)
	at tlc2.REPL.runREPL(REPL.java:151)
	at tlc2.REPL.main(REPL.java:174)

From some investigation it looks like the error for this specific case arises from the size call inside SubsetValue.toSetEnum() which is called from EnumerableValue.getRandomSubset() . It looks like the issue manifests when the set size is greater than what can be handled by a 32 bit int e.g. RandomSubset(3, SUBSET [a:1..8, b:1..4]) throws an error but RandomSubset(3, SUBSET [a:1..8, b:1..3]) doesn’t.

Reproduced in TLC revision 4aff6d2.

[will62794]

Yeah. I originally ran into the error when working on a larger spec, and then produced this smaller repro.

[will62794]

Sounds good, thanks.