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Old 2019-11-13, 22:00   #476
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"Ed Hall"
Dec 2009
Adirondack Mtns

C9416 Posts

In playing with my Colab instance of GMP-ECM with GPU enabled (K80 GPU), I have made some observations:

The K80 shows 832 cores. If I run threads up to half of the cores, vs. over half the cores, the time for the run just about doubles. It is pretty close to constant within those halves. For example, running stage 1 for 5+3,1185L, it takes just about 22 seconds to complete <417 curves at 11e4. >416 curves takes about 41 seconds. Of note, I am using multiples of 32 cores.

Running a single curve without the GPU takes about .4 second. Obviously, running more curves on a single CPU core would sequentially add time - 416 curves by CPU would take about 166 seconds.

This appears to indicate that while the GPU sounds impressive with all its cores, a quad core CPU would keep up with the K80 GPU in stage 1 runs.

Am I missing something here?
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