3 ms·

Thanks, I think that makes sense since 1/x is a non-linear function. I have a follow-up question - what's then the advantage of measuring speed as ops/unit-tim

Thanks, I think that makes sense since 1/x is a non-linear function. I have a follow-up question - what's then the advantage of measuring speed as ops/unit-time (Freq)? How come we don't see 0.25 ns/op as advertised speed on a Processor?

Arelius 9y ago
Exactly. Honestly I don't know. I suspect it's mostly historical and marketing driven. I think CPU clocks are driven by some sort of oscillator, which is likely thought of as a frequency. And ops/unit-time may be a bit ambiguous, since if we try to choose say instructions, not all instructions take the same amount of clock cycles. Additionally from a marketing perspective, I suspect you get a bit of an hz, more is better, sort of increase of numbers. Honestly though I really don't know, this is all just speculation. Similarly video games are often "marketed" in Frames/Second, which is exactly the same problem.
- fermienrico 9y ago
  You're kind of blowing my mind. The more I think, the more stupid I feel. If Freq is non-linear function of period, which it is... then Period is also a non-linear function of Freq. They're an inverse of each other. So, if we're talking about Frequency, then the same argument could be made that Period is non-linear and it cannot be used to compare speed, since Period is 1/f - a non-linear function. wtf is going on here... my brain hurts.
  - Arelius 9y ago
    Yes, that's very true. I think it can be sometimes hard to ground yourself in what the actual thing is you care about. I think here is where experience trying to use the values is helpful, hence my video game example in a sibling thread.
eesmith 9y ago
"How come we don't see 0.25 ns/op as advertised speed on a Processor?" Because different operations take different numbers of cycles and have different latencies. See http://www.agner.org/optimize/instruction_tables.pdf http://www.agner.org/optimize/instruction_tables.pdf for a table of such.

Arelius 9y ago

Exactly. Honestly I don't know. I suspect it's mostly historical and marketing driven. I think CPU clocks are driven by some sort of oscillator, which is likely thought of as a frequency. And ops/unit-time may be a bit ambiguous, since if we try to choose say instructions, not all instructions take the same amount of clock cycles. Additionally from a marketing perspective, I suspect you get a bit of an hz, more is better, sort of increase of numbers. Honestly though I really don't know, this is all just speculation. Similarly video games are often "marketed" in Frames/Second, which is exactly the same problem.

fermienrico 9y ago
You're kind of blowing my mind. The more I think, the more stupid I feel. If Freq is non-linear function of period, which it is... then Period is also a non-linear function of Freq. They're an inverse of each other. So, if we're talking about Frequency, then the same argument could be made that Period is non-linear and it cannot be used to compare speed, since Period is 1/f - a non-linear function. wtf is going on here... my brain hurts.
- Arelius 9y ago
  Yes, that's very true. I think it can be sometimes hard to ground yourself in what the actual thing is you care about. I think here is where experience trying to use the values is helpful, hence my video game example in a sibling thread.

eesmith 9y ago

"How come we don't see 0.25 ns/op as advertised speed on a Processor?" Because different operations take different numbers of cycles and have different latencies. See http://www.agner.org/optimize/instruction_tables.pdf http://www.agner.org/optimize/instruction_tables.pdf for a table of such.