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The MT-Evaluator Virtual
Machine
Kristine Joy Apon, Kai H. Fan, Joanie
Feeney, Peter Laurina, Steve O’Brien,
Gregory Van De Moere
Advisor: Dr. Marco Morazán
Functional Programming

Describing processes such as mathematical notations
and procedures
(define (fact n)
(if (= n 0)
1
(* n (fact (- n 1))) ) )
Functional Programming

Benefits

More intuitive than imperative languages such
as C and Java

Easy to prove correctness of functions

Truly machine independent

Fast prototyping
Disadvantages


Poor virtual memory interaction can make
them slow.
Excessive paging can profoundly affect
performance.
Distributed Virtual Memory System



Tailored for functional languages
implemented completely in software.
Parallelize the engine that evaluates
programs and not individual user code.
Parallelize memory management.
MT Architecture
Virtual Machines

Software that emulates a real machine by
keeping track of state.



Can port software from one machine to
another.
Can execute software designed for a machine
never physically implemented.
The MT evaluator is a switch-based virtual
machine.
MT Evaluator Virtual Machine
Implementation

Heap, stack, symbol table, and code are
objects implemented in C++

Instance variables
For data
 For virtual memory implementation


Public and private methods
Public methods: constructor, data access methods.
 Private Methods: memory management routines.



Paging occurs within these discretized
memory spaces.
No shared memory (either pages or frames)
between spaces.
Paging Policy Considerations

Paging behavior of distributed spaces

Heap


FIFO ≈ LRU (FIFO has less overhead).
Stack
LRU superior to FIFO.
 Uses a special version of LRU without timestamps.


Code

DLL-LRU: LRU employing a circular double-linked
list.
Test 1: Creating a list of 10000
random numbers using FIFO

Empirical Measurements for performance

Heap
40000 accesses
 20000 allocations
 60 faults (.0015 fault rate)


Stack
270013 accesses
 120006 allocations
 99 faults (.0004 fault rate)

Future Work




Comparing FIFO & LRU, other paging
algorithms for code space and garbage
collection.
Implementation of 1st-class functions.
Development of an MT Compiler for
different functional languages.
Design and implementation of a GC
algorithm that exploits the MT
architecture.