Hi Igor. Does the same test work correctlly in a interpreter VM? because I can see:<br><br>ObjectMemory >> newObjectHash<br> "Answer a new 16-bit pseudo-random number for use as an identity hash."<br><br>
lastHash := 13849 + (27181 * lastHash) bitAnd: 65535.<br> ^ lastHash<br><br><br>In which case, it seems that every new hash will be different than the previous one.<br><br>But NewObjectMemory >> newObjectHash<br>
"Derive the new object hash from the allocation pointer. This is less costly than<br> using lastHash because it avoids the read-modify-write cycle to update lastHash.<br> Since the size of eden is a power of two and larger than the hash range this provides<br>
a well-distributed and fairly random set of values."<br> <inline: true><br> ^freeStart >> BytesPerWord<br><br>so...I have no idea, but maybe for two consequently allocated objects, the instVar freeStart can remain with the same value ?<br>
<br><br><br><div class="gmail_quote">On Mon, Aug 1, 2011 at 8:43 AM, Igor Stasenko <span dir="ltr"><<a href="mailto:siguctua@gmail.com">siguctua@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
I found that #testBecomeIdentityHash sometimes failing, sometimes not.<br>
<br>
It seems like VM 'forgets' to produce different identityHash bits for<br>
two consequently allocated objects,<br>
while test assumes that they are always different.<br>
<br>
If i insert a statement (see the code), test no longer fails.<br>
<br>
testBecomeIdentityHash<br>
"Note. The identity hash of both objects seems to change after the become:"<br>
<br>
| a b c d |<br>
<br>
a := 'ab' copy.<br>
b := 'cd' copy.<br>
<br>
>>> [ b identityHash = a identityHash ] whileTrue: [ b := b copy ].<br>
<br>
c := a.<br>
d := b.<br>
<br>
a become: b.<br>
<br>
self<br>
assert: a identityHash = c identityHash;<br>
assert: b identityHash = d identityHash;<br>
deny: a identityHash = b identityHash.<br>
<br>
A simple piece of code reveals the problem:<br>
<br>
(1 to: 20) collect: [:i |<br>
'ab' copy basicIdentityHash ] #(954 954 955 955 956 956 957 957 958<br>
958 959 959 960 960 961 961 962 962 963 963)<br>
<font color="#888888"><br>
<br>
--<br>
Best regards,<br>
Igor Stasenko AKA sig.<br>
<br>
</font></blockquote></div><br><br clear="all"><br>-- <br>Mariano<br><a href="http://marianopeck.wordpress.com" target="_blank">http://marianopeck.wordpress.com</a><br><br>