Code with HVM.log hangs

[Steven]

Step = 0.5
(F2B 1.0) = 1
(F2B 0.0) = 0
(Dbg x) = (HVM.log x x)
(Gen x) = (U60.if (F2B (< x 0.0)) [] (List.cons (Dbg x) (Gen (- x Step))))
Main = (Gen 5.0)

This hangs, and also logs unordered results like:

4.0
1.0
3.0
3.5
2.5
5.0
4.5
1.5
2.0
^C

[Steven]

more minimal example:

(Gen x) = (U60.if (< x 1) [] (List.cons (HVM.log x x) (Gen (- x 1))))
Main = (Gen 2)

This hangs in single thread with debug mode enabled, and (Gen 5) hangs without debug mode enabled.

[Nicolas Abril]

It's unordered because you didnt force a sequential order for the logs like so

(Gen 0) = []
(Gen x) = (Data.List.cons x (Apps.HVM.log x (Gen (- x 1))))
Main = (Gen 5)

or

(Gen 0) = []
(Gen x) = (Apps.HVM.log x (Data.List.cons x (Gen (- x 1))))
Main = (Gen 5)

[Nicolas Abril]

I think it's hanging when a thread calls log for the second time.

Running it with hvm run -t1 hangs every time when reducing the second log

(Gen 0) = []
(Gen x) = (Apps.HVM.log x (Data.List.cons x (Gen (- x 1))))
Main = (Gen 5) // Or any number higher than one

If we give it more threads to work then the iteration at which it hangs changes non-deterministically, probably due to the order that the threads are executed.
The probability of completing without hanging seems to increase with the number of threads.

[Steven]

The behaviors are very different since the recent commits (I was previously on 5e52131). With the previous program, HVM now underflows Gen. The fix that I tried on 5e52131 also works on the new master (05a6984), which evaluates the arguments of a constructor just like those of a function and not let HVM.log do the reduction. With this commit on top of 5e52131 HVM doesn't hang ; with it on 05a6984 HVM still underflows

Edit: oops apparently U60.if also got renamed

[Yan Mendes]

closed as HVM is now HVM2 and this no longer pertains.