Re: bug#22357: grep -f not only huge memory usage, but also huge time cost

[Paul Eggert]

Trevor Cordes wrote:
> On 2016-12-12 Paul Eggert wrote:
> > grep should just work. It is
> > not working now and we need to fix that
>
> By that rationale, the commit that causes the problems for me should be
> backed out as a first step, and then a proper solution should be
> found.

But it may be better to improve on the solution. Backing up is not always the 
best way to move forward, even if a previous step had unwanted consequences.

> This all should be approached from the standpoint that the pre-commit
> state is correct

But the pre-commit state had bad performance in some significant cases. So we 
can't assume it was correct.

> My point being: wouldn't any dfa solution require much
> larger amounts of RAM?

That might be OK these days. It would depend on how much RAM of course. 
Nowadays, trading RAM for CPU time is often a win.

> Perhaps
> necessitating a need for a --optimize-for-ram and --optimize-for-time
> switch choice.

I would rather avoid that. Users will not want to mess with such options. "grep 
should just work."