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FLOPS stands for FLoating-point Operations Per Second and I have some idea what Floating-point is. I want to know what these Operations are? Does +, -, *, / are the only operations or operations like taking logarithm(), exponential() are also FLOs?

Does + and * of two floats take same time? And if they take different time, then what interpretation should I draw from the statement: Performance is 100 FLOPS. How many + and * are there in one second.

I am not a computer science guy, so kindly try to be less technical. Also let me know if I have understood it completely wrong.

Thanks

pkj
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There is no specific set of operations that are included in FLOPS, it's just measured using the operations that each processor supports as a single instruction. The basic arithmetic operations are generally supported, but operations like logarithms are calculated using a series of simpler operations.

For modern computers all the supported floating point operations generally run in a single clock cycle or less. Even if the complexity differs a bit between operations, it's rather getting the data in and out of the processor that is the bottle neck.

The reason that FLOPS is still a useful measure for computing speed is that CPUs are not specialized on floating point calculations. Adding more floating point units in the CPU would drive up the FLOPS, but there is no big market for CPUs that are only good at that.

Guffa
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  • Good answer in general, however, I disagree on the usefulness of FLOPs: Relevant scientific codes running on supercomputers only use about 5% to 10% of the theoretical Tera/Peta-Flops available on the machine. The usefulness of the unit FLOP is even further diminished by the different definitions in use: Is a fused add-multiply one or two FLOPs? (Marketing people: Two, of course!) Do you count single precision or double precision FLOPs? That's an uncertaincy of 4x! My impression is that "Macho"-FLOPs have been more of a marketing argument than a solid performance measurement for many years. – cmaster - reinstate monica Apr 03 '15 at 09:33
  • @cmaster: Naturally any measurement that only looks at a single aspect and is so loosely defined has a limited usefulness. Still, the usefulness is relatively unchanged by changes in technology, compared to for example clock frequency that had its usefulness drastically reduced by the introduction of parallel processing. – Guffa Apr 03 '15 at 09:54