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The world could run on older hardware if software optimization was a priority

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838 points turrini | 2 comments | 13 May 25 10:31 UTC | HN request time: 0.394s | source
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titzer ◴[13 May 25 12:05 UTC] No.43971962[source]▶
I like to point out that since ~1980, computing power has increased about 1000X.

If dynamic array bounds checking cost 5% (narrator: it is far less than that), and we turned it on everywhere, we could have computers that are just a mere 950X faster.

If you went back in time to 1980 and offered the following choice:

I'll give you a computer that runs 950X faster and doesn't have a huge class of memory safety vulnerabilities, and you can debug your programs orders of magnitude more easily, or you can have a computer that runs 1000X faster and software will be just as buggy, or worse, and debugging will be even more of a nightmare.

People would have their minds blown at 950X. You wouldn't even have to offer 1000X. But guess what we chose...

Personally I think the 1000Xers kinda ruined things for the rest of us.

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monkeyelite ◴[13 May 25 13:43 UTC] No.43972915[source]▶
> If dynamic array bounds checking cost 5% (narrator: it is far less than that)

It doesn’t work like that. If an image processing algorithm takes 2 instructions per pixel, adding a check to every access could 3-4x the cost.

This is why if you dictate bounds checking then the language becomes uncompetitive for certain tasks.

The vast majority of cases it doesn’t matter at all - much less than 5%. I think safe/unsafe or general/performance scopes are a good way to handle this.

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1. miloignis ◴[13 May 25 14:34 UTC] No.43973436[source]▶
It's not that simple either - normally, if you're doing some loops over a large array of pixels, say, to perform some operation to them, there will only be a couple of bounds checks before the loop starts, checking the starting and ending conditions of the loops, not re-doing the bounds check for every pixel.

So very rarely should it be anything like 3-4x the cost, though some complex indexing could cause it to happen, I suppose. I agree scopes are a decent way to handle it!

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2. monkeyelite ◴[13 May 25 19:16 UTC] No.43976542[source]▶
You’re describing a situation where I - or a very smart compiler can choose when to bounds check or not to make that intelligent realization.