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Issue with optimized compilation for partially defined mydiv function #54

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Alexander-Schiendorfer opened this Issue Sep 29, 2015 · 1 comment

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@Alexander-Schiendorfer

Alexander-Schiendorfer commented Sep 29, 2015

When trying the user-defined partial function example mydiv from the Coursera class, I noticed some problems with compiler optimizations (also here Gist) :

function var int:mydiv(var int: x, var int: y) = 
  assert(lb(x) >= 0 /\ lb(y) >= 0,
         "Mydiv got wrong arguments",
         let {constraint y != 0 } in 
         safediv(x, y)
);

function var int: safediv(var int: x, var int: y)   :: promise_total = 
  let {
    var 0..ub(x): q;
    var 0..ub(y)-1: r;
    constraint q*y + r = x;
    constraint r < y;
  }  in q;

var int: x;
var int: y; 
var int: z;

constraint x = 7;
constraint y = 1;
constraint z = mydiv(x,y);

% should return z = 7
solve satisfy;

which returns { (7,1,i) | i in 0..7} as solution set when producing optimized FlatZinc.

*. When declaring var 0..ub(y)-1: r; as var int: r;' with optimized FlatZinc, the correct (only) solution(7,1,7)` is returned. Then, the constraints

array [1..3] of int: X_INTRODUCED_5 = [1,-1,-1];
array [1..2] of int: X_INTRODUCED_6 = [1,-1];

are present, whereas they weren't in the original version. The original FlatZinc is obscurely small:

var 0..7: z:: output_var;
solve  satisfy;
  • When compiling the model without the flag for optimized FlatZinc, I get the correct solution set.

I'm using the bundled MiniZinc IDE, Version 0.9.9.

@guidotack

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guidotack commented Sep 30, 2015

Thanks a lot, that was a bug in the optimisation phase of the compiler (completely unrelated to partial functions, but triggered by this example). It will be fixed in the next release (which should have happened today, but there were a few showstoppers like this one).

@guidotack guidotack closed this in aa8347e Oct 5, 2015

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