Hashing "object identities"

[Antoniotti Marco]

Hi Nick.

I am actually hashing DAGs.  I used EQUALP hash tables, every lookup may end up checking entire sub-dags, which would defeat the purpose.

Marco




> On Dec 3, 2017, at 12:25 , Nick Levine <nick at nicklevine.org> wrote:
> 
> For the structures you'll have to use EQUALP. So your question as I understand it is how to incorporate that into lookup of the triples. 
> 
> You might have an EQUALP table which maps each structure into a number, and then the main lookup is keyed on a triple of numbers.
> 
> Or maybe, if speed is more important than space, each structure contains an ID slot -- a unique number -- and you key off that. 
> 
> - nick
> 
>> 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
>> 
>> 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).