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Commit a24478aa authored by Branislav Jansik's avatar Branislav Jansik
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Update energy.md

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...@@ -18,10 +18,19 @@ Core frequency capping is implemented for the Karolina supercomputer: ...@@ -18,10 +18,19 @@ Core frequency capping is implemented for the Karolina supercomputer:
### Performance Impact ### Performance Impact
The performance impact depends strongly on the [arithmetic intensity][1][2] of the job. The performance impact depends on the [arithmetic intensity][1] of the job.
The [arithmetic intensity][2] is a measure of floating-point operations (FLOPs) performed by a given code (or code section) relative to the amount of memory accesses (Bytes) that are required to support those operations. It is defined as a FLOP per Byte ratio (F/B). It is a characteristics of the particular computational algorithm.
In general, the processor frequency capping has low performance impact for computation with intensity below
the [ridge point][2], such as memory bound computations. For intensive, CPU bound computations, the impact is directly
proportional to the frequency reduction.
On Karolina, relative time increase factor up to 1.3 is observed for intensive workloads on CPU, up to 1.1 on GPU. No slowdown is observed for memory bound workloads.
### Energy Saved ### Energy Saved
The enegy efficiency in floating point operations per joule is increased by about 30% for CPU workloads, about 25% for GPU workloads.
## Barbora ## Barbora
None implemented yet. None implemented yet.
...@@ -34,5 +43,5 @@ None implemented yet. ...@@ -34,5 +43,5 @@ None implemented yet.
None implemented yet. None implemented yet.
[1]: https://people.eecs.berkeley.edu/~kubitron/cs252/handouts/papers/RooflineVyNoYellow.pdf [1]: https://en.wikipedia.org/wiki/Roofline_model
[2]: https://en.wikipedia.org/wiki/Roofline_model [2]: https://people.eecs.berkeley.edu/~kubitron/cs252/handouts/papers/RooflineVyNoYellow.pdf
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