alt Hacker NewsI have a lot of issues with this one:
https://lawsofsoftwareengineering.com/laws/premature-optimiz...
It leaves out this part from Knuth:
>The improvement in speed from Example 2 to Example 2a is only about 12%, and many people would pronounce that insignificant. The conventional wisdom shared by many of today’s software engineers calls for ignoring efficiency in the small; but I believe this is simply an overreaction to the abuses they see being practiced by penny-wise- and-pound-foolish programmers, who can’t debug or maintain their “optimized” programs. In established engineering disciplines a 12% improvement, easily obtained, is never considered marginal; and I believe the same viewpoint should prevail in software engineering. Of course I wouldn’t bother making such optimizations on a one-shot job, but when it’s a question of preparing quality programs, I don’t want to restrict myself to tools that deny me such efficiencies.
Knuth thought an easy 12% was worth it, but most people who quote him would scoff at such efforts.
Moreover:
>Knuth’s Optimization Principle captures a fundamental trade-off in software engineering: performance improvements often increase complexity. Applying that trade-off before understanding where performance actually matters leads to unreadable systems.
I suppose there is a fundamental tradeoff somewhere, but that doesn't mean you're actually at the Pareto frontier, or anywhere close to it. In many cases, simpler code is faster, and fast code makes for simpler systems.
For example, you might write a slow program, so you buy a bunch more machines and scale horizontally. Now you have distributed systems problems, cache problems, lots more orchestration complexity. If you'd written it to be fast to begin with, you could have done it all on one box and had a much simpler architecture.
Most times I hear people say the "premature optimization" quote, it's just a thought-terminating cliche.
Replies
> In many cases, simpler code is faster, and fast code makes for simpler systems. (...)
I wholeheartedly agree with you here. You mentioned a few architectural/backend issues that emerge from bad performance and introduce unnecessary complexity.
But this also happens in UI: Optimistic updates, client side caching, bundling/transpiling, codesplitting etc.
This is what happens when people always answer performance problems with adding stuff than removing stuff.
> I suppose there is a fundamental tradeoff somewhere, but that doesn't mean you're actually at the Pareto frontier, or anywhere close to it. In many cases, simpler code is faster, and fast code makes for simpler systems.
Just a little historic context will tell you what Knuth was talking about.
Compilers in the era of Knuth were extremely dumb. You didn't get things like automatic method inlining or loop unrolling, you had to do that stuff by hand. And yes, it would give you faster code, but it also made that code uglier.
The modern equivalent would be seeing code working with floating points and jumping to SIMD intrinsics or inline assembly because the compiler did a bad job (or you presume it did) with the floating point math.
That is such a rare case that I find the premature optimization quote to always be wrong when deployed. It's always seems to be an excuse to deploy linear searches and to avoid using (or learning?) language datastructures which solve problems very cleanly in less code and much less time (and sometimes with less memory).
[dead]
I absolutely cannot stand people who recite this quote but has no knowledge of the sentences that come before or after it: "We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunities in that critical 3%."