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Forums > Digital IC > Floorplanning, Place and route

Subject: tip of the week: improve run time during initial placement
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lisiang
Moderator
Posts: 48
Online: User is Offline
12/05/2006 1:50 AM  

You can cut your run time by up to 3x (for 500k instances) by not doing scan recordering during placeDesign.  You can do the following
.
. SETUP UP YOUR SCAN IN & SCAN OUT
.
setPlaceMode -noReorderScan -modulePlan
placeDesign -with_your_own_option
scanReorder
optDesign -preCts

With the above flow, the run time is reduced at the same time congestion & timing do not get worst.

li siang
EngHan
Posts: 65
Online: User is Offline
12/31/2006 8:32 PM  
Hi Li Siang,

I tried out your suggestion, but does not see improvement. The design is bigger than 500K during placeDesign. Maybe I am using scandef. There are many scan chaisn due to the use of scan compressor. I think it is a easier flow to use scandef than to define scan-in and scan-out in Encounter especially with scan compressor the scan-ins and scan-outs are at defined at hier ports.

Do you have any idea why disable scan reordering can make placeDesign with modulePlan run faster?

Regards,
Eng Han
lisiang
Moderator
Posts: 48
Online: User is Offline
1/01/2007 12:00 PM  
i assumed you are using -inPlaceOpt with -modulePlan.

-modulePlan wil run placement multi-time with the -inPlaceOpt to improve timing. Each re-placement will cause a scan recordering. Thus turning off the scan recordering will save some run time. If you design is not timing critical, then the re-placement might not happen and you might not see the run time saving.

li siang
EngHan
Posts: 65
Online: User is Offline
1/02/2007 10:23 AM  
Hi Li Siang,

I am not using "-inPlaceOpt" with -modulePlan. I using optDesign after placeDesign. This is the reason why I don't see improvement in runtime.

In your experience, do you prefer to use "-inplaceOpt"? Somehow it appear to me that running in two steps give better result.
Regards,
Eng Han
lisiang
Moderator
Posts: 48
Online: User is Offline
1/02/2007 10:48 AM  
it is design dependent. In general -inPlaceOpt with -modulePlan works pretty well due to the replacement & re-opt. In some of the block i did, i found the following woked better (gave better timing)

placeDesing -modulePlan
optDesign -preCts
placeDesign -incr
optDesign -preCts

li siang
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Forums > Digital IC > Floorplanning, Place and route > tip of the week: improve run time during initial placement


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