Re: [gobo-eiffel-develop] Crash in DS_HASH_TABLE

[Eric B. <er...@go...>]

Wolfgang Jansen wrote:
> Eric Bezault wrote:
>> Wolfgang Jansen wrote:
>>> some time ago I already asked a related question and you
>>> gave an answer. But I may have misunderstood something.
>>> The problem is as follows. I have a class like
>>>
>>>   class C
>>>   inherit
>>>     DS_EQUALITY_TESTER [KEY_TYPE]
>>>       redefine test
>>>     end
>>>
>>>   feature
>>>
>>>     table: DS_HASH_TABLE [ITEM_TYPE,KEY_TYPE]
>>>
>>>     make is
>>>       do
>>>         create table.make_with_equality_testers(1000, Void, Current)
>>>       end
>>>
>>>     build(k: KEY_TYPE): ITEM_TYPE is
>>>       do
>>>         if table.has(k) then
>>>           Result := table.item(k)
>>>         else
>>>           create Result.make(k)
>>>           table.force(Result,k)
>>>         end
>>>       end
>>>
>>>     test(u,v: STRING) is
>>>       do
>>>         -- I would like to do this more intelligent,
>>>         -- but this is a different problem
>>>         Result := u = v
>>>       end
>>>
>>>    -- other features
>>>
>>>   end
>>>
>>> This works very well for some time (hundreds of calls)
>>> but then routine `search_position' enters an infinite loop:
>>> Lines 590,591 of DS_SPARSE_CONTAINER are
>>>   prev := i
>>>   i := clashes_item(i)
>>> and have the effect that `prev=1', `i=1', i.e. no further
>>> progress happens. A particular observation:
>>> `table' has currently 1028 elements.
>>>
>>> So, what has gone wrong and how can I fix the bug?
>> Is the value of the hash_code of your keys changing while
>> these keys are used in the hash table?
>>
> I don't know, the key type is ET_FEATURE.
> So, you may answer this best yourself.

No, the hash_code is set once and for all when creating the feature
object.

Here are more questions:

Do you change the value of `key_equality_tester' in your hash table
at some point in your program?

If you initially create the hash table with a capacity of 2000
instead of 1000, does it still crash? If so, does it crash with
the same number of items already inserted?

Do you have some code that I can use to try to reproduce the problem?
I guess that the code above will not help me (the feature `test' is
using STRINGs instead of ET_FEATUREs).

-- 
Eric Bezault
mailto:er...@go...
http://www.gobosoft.com