On 2 Sep 2013, at 12:47 AM, Marcel Weiher <marcel.wei...@gmail.com> wrote:
> This gets (mis-)quoted out of context way too much (my emphasis):
>
> "We should forget about small efficiencies, say about 97% of the time:
> premature optimization is the root of all evil”
>
> It goes on as follows:
>
> "Yet we should not pass up our opportunities in that critical 3%. A good
> programmer will not be lulled into complacency by such reasoning, he will be
> wise to look carefully at the critical code; but only ***after*** that code
> has been identified. It is often a mistake to make ***a priori*** judgments
> about what parts of a program are really critical, since the universal
> experience of programmers who have been using measurement tools has been that
> their intuitive guesses fail.
...
[Emphases added. I hope the edits do not misrepresent your position.]
This is wisdom. But the aphorism is not in even rhetorical opposition to — it
is a reinforcement of — what Knuth restated at length. The key word is
_premature_, doing what should be done **after**, not to be done **a priori**.
The opposition ("Yet..."), if any, is against taking the aphorism as an
absolute, ignoring that it warns of prematurity, not optimization or
instrumentation. Everybody who quotes it understands that, and joins Knuth in
demanding measurement before jumping to conclusions — which are almost always
wrong. And premature.
I confess I am sheepish about applying Talmudic exegesis to what are after all
only the opinions of one man, however distinguished. The appropriate issue is
not what his opinions are (were? I hope not), but what is the best practice.
— F
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