Hashing "object identities"

[Antoniotti Marco]

Weak hash tables must be used; no questions about this.  The issue is the key of such hash tables.

I may be missing something obvious, of course...

Cheers
—
MA




> On Dec 3, 2017, at 12:48 , Daniel Kochmański <daniel at turtleware.eu> wrote:
> 
> 
> 
> On 03.12.2017 12:41, Antoniotti Marco wrote:
>> Let me also add that I am being deliberately withholding information on what exactly I am working on/fooling around with :)  There is an obvious solution based on keeping a table of such objects; alas, it would require manually garbage collecting it.  I’d like to let the GC do the work.
> What about weak hash tables? They are supported by most implementations (and have portability layer in form of a library trivial-garbage).
>> 
>> Cheers
>> —
>> MA
>> 
> Regards,
> Daniel
>> 
>> 
>> 
>>> On Dec 3, 2017, at 12:38 , Antoniotti Marco <antoniotti.marco at disco.unimib.it> wrote:
>>> 
>>>> On Dec 3, 2017, at 12:27 , Jason Cornez <jcornez at alum.mit.edu> wrote:
>>>> 
>>>> Add an integer slot on the structs; hash on that?  -Jason
>>> I forgot to mention it.  THAT is another thing I want to avoid because I need to share subgraphs (DAGs).  I need to hash on the “object identity”.
>>> 
>>> Cheers
>>> —
>>> MA
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>>> Sent from my iPhone
>>>> 
>>>>> On 3 Dec 2017, at 12:02, Antoniotti Marco <antoniotti.marco at disco.unimib.it> wrote:
>>>>> 
>>>>> Hi
>>>>> 
>>>>> I am fooling around with a problem that eventually will have to use a hash table on “triples” of “integers” and “structures".  Triples I can portably pass to the EQUAL hash table.  I cannot use an EQUALP hash table, because I would end up wasting to much time.
>>>>> 
>>>>> Here is the rub:  my triples <N, O1, O2> need to use the “object identity” of O1 and O2 (two structs).  I could switch to an EQL hash table keyed on (HASH-TRIPLE-KEY N O1 O2).  How would you proceed (or write HASH-TRIPLE), while staying as much portable as possible?  As you well know SXHASH is practically useless.
>>>>> 
>>>>> Thanks
>>>>> —
>>>>> Marco
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> --
>>>>> Marco Antoniotti, Associate Professor        tel.    +39 - 02 64 48 79 01
>>>>> DISCo, Università Milano Bicocca U14 2043        http://bimib.disco.unimib.it
>>>>> Viale Sarca 336
>>>>> I-20126 Milan (MI) ITALY
>>>>> 
>>>>> Please check: http://cdac2018.lakecomoschool.org
>>>>> Please check: http://troncopackage.org
>>>>> 
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>>>>> Please do not forward this email without asking me first (cum grano salis).
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>> 
>>> --
>>> Marco Antoniotti, Associate Professor		tel.	+39 - 02 64 48 79 01
>>> DISCo, Università Milano Bicocca U14 2043		http://bimib.disco.unimib.it
>>> Viale Sarca 336
>>> I-20126 Milan (MI) ITALY
>>> 
>>> Please check: http://cdac2018.lakecomoschool.org
>>> Please check: http://troncopackage.org
>>> 
>>> Please note that I am not checking my Spam-box anymore.
>>> Please do not forward this email without asking me first (cum grano salis).
>> --
>> Marco Antoniotti, Associate Professor		tel.	+39 - 02 64 48 79 01
>> DISCo, Università Milano Bicocca U14 2043		http://bimib.disco.unimib.it
>> Viale Sarca 336
>> I-20126 Milan (MI) ITALY
>> 
>> Please check: http://cdac2018.lakecomoschool.org
>> Please check: http://troncopackage.org
>> 
>> Please note that I am not checking my Spam-box anymore.
>> Please do not forward this email without asking me first (cum grano salis).
>> 
>> 
>> 
>> 
>> 
> 
> 

--
Marco Antoniotti, Associate Professor		tel.	+39 - 02 64 48 79 01
DISCo, Università Milano Bicocca U14 2043		http://bimib.disco.unimib.it
Viale Sarca 336
I-20126 Milan (MI) ITALY

Please check: http://cdac2018.lakecomoschool.org
Please check: http://troncopackage.org

Please note that I am not checking my Spam-box anymore.
Please do not forward this email without asking me first (cum grano salis).