[Python-Dev] AlternativeImplementation forPEP292:SimpleString Substitutions (original) (raw)

Gareth McCaughan gmccaughan at synaptics-uk.com
Mon Sep 13 14:32:00 CEST 2004

On Saturday 2004-09-11 08:35, Stephen J. Turnbull wrote:

>> But [efficiency], as such, is important only to efficiency >> fanatics.

Gareth> No, it's important to ... well, people to whom efficiency Gareth> matters. There's no need for them to be fanatics. If it matters just because they care, they're fanatics. If it matters because they get some other benefit (response time less than the threshold of hotice, twice as many searches per unit time, half as many boxes to serve a given load), they're not. 's talk of many ways to do things "and Python should account for most of them" strikes me as fanaticism by that definition; the vast majority of developers will never deal with the special cases, or write apps that anticipate dealing with huge ASCII strings. Those costs should be borne by the developers who do, and their clients.

I am unconvinced that "the vast majority of developers" will not have work to do that involves a large volume of ASCII data ... but I'm not sure this is something either of us is in a position to know. (If it turns out that you're just completing a PhD thesis entitled "Use of large-volume string data among software developers", or something, then please accept my apologies for guessing wrong and enlighten me!)

I apologize for shoehorning that into my reply to you.

That's OK.

>> The question is, how often are people going to notice that when >> they have pure ASCII they get a 100% speedup [...]?

Gareth> Why is that the question, rather than "how often are Gareth> people going to benefit from getting a 100% speedup when Gareth> they have pure ASCII"? Because "benefit" is very subjective for one person, and I don't want to even think about putting coefficients on your benefit versus mine. If the benefit is large enough, a single person will be willing to do the extra work. The question is, should all Python users and developers bear some burden to make it easier for that person to do what he needs to do?

"Burden" is just as subjective as "benefit". But let's take a look at these burdens and benefits.

Perhaps I'm being obtuse, but it's far from clear to me that this is a net loss for Python users at large. In any case, the burdens seem less likely to be noticed than the benefits.

I think "notice" is something you can get consensus on. If a lot of people are noticing the difference, I think that's a reasonable rule of thumb for when we might want to put "it", or facilities for making individual efforts to deal with "it" simpler, into "standard Python" at some level. If only a few people are noticing, let them become expert at dealing with it.

But even if "noticing the difference" is the key point, it is a mistake (I think) to make it specifically "noticing that when they have pure ASCII they get a 100% speedup". Hence my comment quoted below:

Gareth> Or even "how often are people going to try out Python on Gareth> an application that uses pure-ASCII strings, and decide to Gareth> use some other language that seems to do the job much Gareth> faster"?

See? You're now using a "notice" standard, too. I don't think that's an accident.

It isn't. It's because I was replying to someone who apparently took "notice" standards as the only relevant ones, in order to point out that even with that assumptions there are relevant questions other than "will anyone notice getting a speedup when their data are pure ASCII?".

And I, in turn, apologize for shoehorning all that into the word "even". :-)

I still think, though, that a "notice" standard makes for bad designs. Most people would not notice if all floating-point operations gave results with the last couple of bits wrong, but it is a good thing that they don't. Some people wouldn't notice but would get badly unsatisfactory results. Some people would notice but would find it impractical to work around the problems because that would mean tons of code and major losses in speed.

Most people would not notice if by inserting the magic word "wibble" at the start of their programs they could make them 10 times faster, but if for some weird reason it were possible to make that so (but not possible to provide the speedup for programs without "wibble") then it should be done.

What people notice is easier to define and to measure than what actually makes a difference to them. That is not enough reason to treat it as the only criterion.

-- g

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