why we need path grouping

[manikanta.9332]

Hello all,


Why we need path grouping?

any advantages?


Thanks........

 

[englishdogg]

i am not sure at which stage do you refer this question for synthesis, placement, optimization etc..
But anyways at either stage this is important and really helps in closing the timing for a specific design.

Basically from my understanding and experience so far EDA tools work better under a path group structure. Ideally under the hood all these paths are made under a each clock and the tool engine is made to work on these paths relating to a clock.

Now in a design there will usally be at max 20% of the paths which are critical to close timing for. Path grouping them together enables an engineer to make the tool focus on these paths, add more pessimism, weight etc and also enables that the tool engine look at these path with priority and fix the same.

I see that these are only advantages to doing this always; the disadvantage that I see is a bit of increase in runtime depending on the number of paths and its slack / clock freq plus engineers effort to create these path groups.

cheers!!

 

[artmalik]

Grouping the path is better performance of the design from a timing prespective. It needs an understanding of the design. You can group certain set of paths to help the the tools to better optimize the design.

i am not sure at which stage do you refer this question for synthesis, placement, optimization etc..
But anyways at either stage this is important and really helps in closing the timing for a specific design.

Basically from my understanding and experience so far EDA tools work better under a path group structure. ideally under the hood all these paths are made under a each clock and the tool engine is made to work on these paths relating to a clock.

Now in a design there will usally be at max 20% of the paths which are critical to close timing for. Path grouping them together enables an engineer to make the tool focus on these paths, add more pessimism, weight etc and also enables that the tool engine look at these path with priority and fix the same.

I see that these are only advantages to doing this always; the disadvantage that i see is a bit of increase in runtime depending on the number of paths and its slack / clock freq plus engineers effort to create these path groups.

cheers!!

- - - Updated - - -

Grouping the path is better performance of the design from a timing prespective. It needs an understanding of the design. You can group certain set of paths to help the the tools to better optimize the design.

i am not sure at which stage do you refer this question for synthesis, placement, optimization etc..
But anyways at either stage this is important and really helps in closing the timing for a specific design.

Basically from my understanding and experience so far EDA tools work better under a path group structure. ideally under the hood all these paths are made under a each clock and the tool engine is made to work on these paths relating to a clock.

Now in a design there will usally be at max 20% of the paths which are critical to close timing for. Path grouping them together enables an engineer to make the tool focus on these paths, add more pessimism, weight etc and also enables that the tool engine look at these path with priority and fix the same.

I see that these are only advantages to doing this always; the disadvantage that i see is a bit of increase in runtime depending on the number of paths and its slack / clock freq plus engineers effort to create these path groups.

cheers!!

 

[Rama krishna k]

Hi,
we do path grouping at place stage.
path grouping is very useful for timing critical tiles.
but run time will increase by 20%.

command in ICC:
group_path

thanks
Rama Krishna

 

[rdk28]

How to decide how much weight has to apply for group_path?
Weight is in between 0 to 100. But how to choose appropriate weight value?

 

[kirteshmiet]

Hi rdk28,

If you see a path is critical then you will give it more wight depends on the viloation , if it is closer to time period then we will give 100 like that we need to in my understanding. correct me some body if i am wrong.