[Vm-dev] VM Maker: VMMaker.oscog-dtl.71.mcz

squeak-dev-noreply at lists.squeakfoundation.org squeak-dev-noreply at lists.squeakfoundation.org
Sat Jun 4 20:03:07 UTC 2011

Dave Lewis uploaded a new version of VMMaker to project VM Maker:

==================== Summary ====================

Name: VMMaker.oscog-dtl.71
Author: dtl
Time: 4 June 2011, 1:27:56 am
UUID: f888ab51-e5b6-48f9-b48b-30f92e61ee50
Ancestors: VMMaker.oscog-eem.70

Montgomery multiplication bug fix from <http://lists.squeakfoundation.org/pipermail/vm-dev/2011-June/008350.html>

Date: Sat, 4 Jun 2011 00:29:37 +0200
From: Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com>
To: Squeak Virtual Machine Development Discussion <vm-dev at lists.squeakfoundation.org>
Subject: [Vm-dev] BUG in Montgomery multiplication

Recent addition, montgomery multiplication, has a bug:
it fails to correctly take last carry into account...

You can see it with this example (if you have the Smalltalk mock up) :

| m mInv a b |
m := 15485863.
mInv := 256 - ((m bitAnd: 255) reciprocalModulo: 256).
a := 8826019 digitMontgomeryTimes: 8826019 modulo: m mInvModB: mInv.
b := 8826019 naiveMontgomeryTimes: 8826019 modulo: m mInvModB: mInv.
self assert: a = b

Correct result is given by naive mock up : 10626344
The primitive gives a wrong result.

I attach a correction for the LargeInteger plugin (and for the
Smalltalk mock up too).

Sorry for uncomplete tests.
Please, update VMMaker ASAP.


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