Re: join regression failure on cygwin

Tom Lane wrote:
> I wrote:
>   
>> Andrew Dunstan <andrew@dunslane.net> writes:
>>     
>>> It appears on Googling a bit that the erand48() is buggy in that it 
>>> requires the seed to have been initialized with srand48() or it will 
>>> constantly return 0.0.
>>>       
>
>   
>> Huh, and that sends us into an infinite loop?  I'll take a look at that.
>> Even though it's surely nonrandom, it doesn't seem like pathological
>> behavior of the RNG should wedge us completely.
>>     
>
> The answer is that a constant RNG result sends this bit of
> geqo_selection() into a tight loop:
>
>     int         first,
>                 second;
>
>     first = linear(root, pool->size, bias);
>     second = linear(root, pool->size, bias);
>
>     if (pool->size > 1)
>     {
>         while (first == second)
>             second = linear(root, pool->size, bias);
>     }
>
> Not sure if it's worth trying to do something about that, or exactly
> what we'd do anyway.  Even if we hacked this up somehow, a constant RNG
> result would pretty much break GEQO for any useful purpose.  So it could
> be argued that having the regression tests fail here is a good thing...
>
>             
>   

Right. Let's let sleeping dogs lie. I think at most a code comment is 
the only action called for.

cheers

andrew