@@ -21,15 +21,13 @@ Core frequency capping is implemented for the Karolina supercomputer:
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@@ -21,15 +21,13 @@ Core frequency capping is implemented for the Karolina supercomputer:
The performance impact depends on the [arithmetic intensity][1] 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.
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
In general, the processor frequency capping has low performance impact for memory bound computations with intensity below the [ridge point][2]. For CPU bound computations with intensity above the [ridge point][2], the impact is directly proportional to the frequency reduction.
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.
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. The efficiency depends on the arithmetic intensity, however energy savings are always achieved.
The enegy efficiency in floating point operations per energy unit is increased by about 30% for CPU workloads, about 25% for GPU workloads. The efficiency depends on the arithmetic intensity, however energy savings are always achieved.