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AR# 37699

12.2 I noticed a drop in performance when I use Multi-threading

Description

When I implement a design with the multithreading activated and then again with the multithreading not activated for MAP and PAR, the results are different.

I can confirm that the results are different because the timing scores are different.

I had thought that using the multithreading would just speed up the implementation but not change the result.

Is it expected behavior that the results are not the same?

For MAP I used -mt 2 and PAR with -mt 4. 

Solution

This is an expected result if you are using multithreading for PAR, A drop in performance by about 1% should be expected.

When the Router algorithms works in parallel, there will be multiple nets being routed at the same time while keeping the resources free, which could lead to a slight drop in performance.

Please note that the main objective behind multi-threading is to reduce run time.

Multi-threading should be used if you are still in the design process but once you have your final design, you can run PAR without multi-threading for extra performance gain and to improve the slacks. 

Multi-threading for the MAPPER should give roughly the same results as when it is run without multi-threading.
AR# 37699
Date Created 08/26/2010
Last Updated 07/31/2014
Status Active
Type Known Issues
Tools
  • ISE Design Suite - 12.2