[MLton-user] out of memory

[Matthew Fluet]

On Tue, Jun 1, 2010 at 12:18 PM, Sean McLaughlin <seanmcl at gmail.com> wrote:
>   I'm getting an out-of-memory error from MLton, though I have 4GB of
> memory.  I don't understand it because my program
> is significantly smaller than the MLton source.  Is there a way around this?
>
>      ssa2Simplify starting
>         typeCheck starting
>         typeCheck finished in 0.55 + 0.00 (0% GC)
>         deepFlatten starting
> Out of memory.  Unable to allocate heap with 1,192,034,304 bytes.

There are some performance issues with the deep flatten pass, where it
consumes an excessive amount of memory, as you observe.  See some
notes at the end of
  http://mlton.org/DeepFlatten

The simplest course of action is to compile with "-drop-pass deepFlatten".

You are also running up against the maximum amount of contiguous
memory that you can get from the operating system.  Due to MLton's
heap resizing policy, it can sometimes grow one heap so large that it
can't allocate another (larger) heap.  You can also try compiling with
"@MLton may-page-heap true", which will allow MLton to write the heap
to a temporary file, free the heap, and then try to allocate a new
heap in a less constrained virtual address space.  MacOSX should be
able to give you about 2.1GiB of heap.  But, if DeepFlatten is
seriously over allocating, then that might not help.

In any case, if you can send a snapshot of the program that
demonstrates the out-of-memory, then it might help to have another
example of the issue.