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Visitor
Posts: 3
Registered: ‎12-14-2017
Accepted Solution

performance per watt - energy efficiency.

Given an architecture A1 and a program P : running P on A1 takes T1 seconds while consuming w1 watts (E1 = w1.T1).

 

 

On the other hand, given an architecture A2 and a program P (same as above) : running P on A2 takes T2 seconds while consuming w2 watts (E2 = w2.T2)

 

what is the best way (formulas) to conclude, if possible, the below metrics :

  • Performance per watt for A1 and A2? is it reasonable to assume that performance is the execution time of P.

  • performance per watt PPW ratio i.e. by how much the PPW of A1 is better/worse than the PPW of A2.

  • how to deduce conclude the energy efficiency ratio e.g. by how much A1 is more/less energy efficient than A2.

Thanks.


Accepted Solutions
Scholar
Posts: 2,614
Registered: ‎04-26-2015

Re: performance per watt - energy efficiency.

(1) Normally performance would be inverse of execution time (ie lower time = more performance). As such, PPW = 1/E.

 

(2) The normal formula would be PPW1/PPW2. Suppose w1 = 2W, T1 = 0.1s (FPGA implmentation) , T2 = 80W, T2 = 0.01s (CPU implementation). The E1 = 0.2J, E2 = 0.8J, PPW1 = 5/J, PPW2 = 1.25/J, and PPW ratio = 4.

 

(3) This is exactly the same as 2; for the same power A1 does four times as much work.

View solution in original post


All Replies
Scholar
Posts: 2,614
Registered: ‎04-26-2015

Re: performance per watt - energy efficiency.

(1) Normally performance would be inverse of execution time (ie lower time = more performance). As such, PPW = 1/E.

 

(2) The normal formula would be PPW1/PPW2. Suppose w1 = 2W, T1 = 0.1s (FPGA implmentation) , T2 = 80W, T2 = 0.01s (CPU implementation). The E1 = 0.2J, E2 = 0.8J, PPW1 = 5/J, PPW2 = 1.25/J, and PPW ratio = 4.

 

(3) This is exactly the same as 2; for the same power A1 does four times as much work.