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class Philosopher module Philosophers {
var left: Fork;
var right: Fork;
method init(f1: Fork, f2: Fork)
requires f1!=null && f2!=null;
requires acc(this.*);
ensures valid;
ensures getLeft()==f1 && getRight()==f2;
{
left := f1;
right := f2;
fold valid;
}
method run()
requires valid;
requires acc(getLeft().mu, 10);
requires acc(getRight().mu, 10);
requires waitlevel << getLeft().mu;
requires waitlevel << getRight().mu;
requires getLeft().mu << getRight().mu;
{
while(true)
invariant valid && acc(getLeft().mu, 10) && acc(getRight().mu, 10) && waitlevel << getLeft().mu && waitlevel << getRight().mu && getLeft().mu << getRight().mu;
{
unfold valid;
acquire left;
acquire right;
//eat
release left;
release right;
fold valid;
}
}
function getLeft(): Fork
requires valid;
ensures result!=null;
{
unfolding valid in left
}
function getRight(): Fork
requires valid;
ensures result!=null;
{
unfolding valid in right
}
predicate valid {
acc(left) && acc(right) && left!=null && right!=null
}
}
class Fork module Dining {
invariant true;
}
class Program module Main {
method main(){
// create forks
var f1 := new Fork;
var f2 := new Fork;
var f3 := new Fork;
share f1;
share f2 above f1;
share f3 above f1, f2;
// create philosophers
var aristotle := new Philosopher;
call aristotle.init(f1, f2);
var plato := new Philosopher;
call plato.init(f2, f3);
var kant := new Philosopher;
call kant.init(f1, f3);
assert f2.mu << f3.mu;
// start eating
fork tk0 := aristotle.run();
fork tk1 := plato.run();
fork tk2 := kant.run();
// everyone's done
join tk0;
join tk1;
join tk2;
}
}
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