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 Difference results when re-run placedesign 

Last post Wed, Mar 22 2006 6:03 AM by archive. 5 replies.
Started by archive 22 Mar 2006 06:03 AM. Topic has 5 replies and 2109 views
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  • Wed, Mar 22 2006 6:03 AM

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    Difference results when re-run placedesign Reply

    I've got every time a difference result when I ran placedesign (related to congestion) after I've changed some power grid even though the same placementguides have been used.
    My question is how can I specify the startpoint  (sheetfactor ??? ) so that the placedesign should start at the same point.

    Thanks.


    Originally posted in cdnusers.org by DN
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  • Wed, Mar 22 2006 6:27 PM

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    RE: Difference results when re-run placedesign Reply

    Hi DN .

    As we know that several factors will involved which cause difference in  results.

    BTW I dent get your changing topics on power grid ??

    There are some default options which play a very imported role during placement and preplacement  optimization.

    I think that you are have explicitly specified (noTimingDriven) option in setPlaceMode.

    Are you expecting default RC factor setting , if YES then below is the method to set it.

    ##### Set RC Factor #####

    setRCFactor -defcap 1.000 -detcap 1.000 -res 1.000

     

    FYI . suggestions from manual :

    Examples

    _ The following commands perform non-timing-driven placement:

    setPlaceMode -noTimingDriven

    placeDesign

    _ The following commands disable scan chain reordering:

    setPlaceMode -noReorderScan

    placeDesign

    _ The following command disables the pre-placed buffer tree removal:

    placeDesign -noPrePlaceOpt

    _ The following command enables the in-place optimization flow:

    placeDesign -inPlaceOpt

    _ After the design is placed, the following command performs incremental placement, and

    disables the pre-placed buffer tree removal:

    placeDesign -incremental

     

    Let me know if you need anything more.

    Reg.
    Mohan Ch


    Originally posted in cdnusers.org by mohanch007
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  • Wed, Mar 22 2006 6:51 PM

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    RE: Difference results when re-run placedesign Reply

    Posted By mohanch007 on 3/22/2006 6:27 PM

    Hi DN .

    As we know that several factors will involved which cause difference in  results.

    BTW I dent get your changing topics on power grid ??

    There are some default options which play a very imported role during placement and preplacement  optimization.

    I think that you are have explicitly specified (noTimingDriven) option in setPlaceMode.

    Are you expecting default RC factor setting , if YES then below is the method to set it.

    ##### Set RC Factor #####

    setRCFactor -defcap 1.000 -detcap 1.000 -res 1.000

     

    FYI . suggestions from manual :

    Examples

    _ The following commands perform non-timing-driven placement:

    setPlaceMode -noTimingDriven

    placeDesign

    _ The following commands disable scan chain reordering:

    setPlaceMode -noReorderScan

    placeDesign

    _ The following command disables the pre-placed buffer tree removal:

    placeDesign -noPrePlaceOpt

    _ The following command enables the in-place optimization flow:

    placeDesign -inPlaceOpt

    _ After the design is placed, the following command performs incremental placement, and

    disables the pre-placed buffer tree removal:

    placeDesign -incremental

     

    Let me add few more comments on "placedesign" command :

    Based on your explanation not only RC extraction tunes placement but also timing analysis, trail routing and placement option settings.

    So you also need to set

    setPrerouteAsObs ( example for placement obstructions)

    setPlaceMode ( you can specify max touting layer )

    Trial Route Option (you need to specify same for every trail).

    Let me know how your trail route congestion report was every time you run.

    Reg.
    Mohan Ch




    Originally posted in cdnusers.org by mohanch007
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  • Thu, Mar 23 2006 12:36 AM

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    RE: Difference results when re-run placedesign Reply

    Thanks for your quickly reponses!

    I know that several factor will involve that cause diffrence in result but I'm 
    using the same options, same guides, same netlist,... from the previous run.
    And it looks like the congestion is changing every time because some modules
    are placed in an another areas.
    The result has not much impact for the timing in generally. But for a high frequent design when a little bit change of congestions can harm the timing clean on some critical paths.
    For more details what I've used:
    - cadence_fe 04.20-s315_1_USR2
    - Hierarchy netlist
    - Timingdriven
    - nopreplaceopt
    - noreordescan

    Regards,


    Originally posted in cdnusers.org by DN
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  • Thu, Mar 23 2006 2:27 AM

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    RE: Difference results when re-run placedesign Reply

    Hi ,
    I seems that you agreed that you have changed the placement of modules or fp. causing the same, As you know that trail route choose different paths when module placement change.
    suggesion : try with "-incremental" option.
    Yes I too agree that global congestion effects every design .
    see the cause and avoid it by placing density screen .


    Originally posted in cdnusers.org by mohanch007
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  • Thu, Mar 23 2006 2:28 AM

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    RE: Difference results when re-run placedesign Reply

    Hi ,
    I seems that you agreed that you have changed the placement of modules or fp. causing the same, As you know that trail route choose different paths when module placement change.
    suggesion : try with "-incremental" option.
    Yes I too agree that global congestion effects every design .
    see the cause and avoid it by placing density screen .

    Thanks , Non -AE


    Originally posted in cdnusers.org by mohanch007
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  • Thu, Mar 23 2006 3:21 AM

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    RE: Difference results when re-run placedesign Reply

    Hi I got you point what you mean in your mail,
    I suggest you to add "Fence" option in your design instead of guide-OK
    (The module is a hard constraint in the core design area.)
    Note: Fence groups can potentially cause overlaps that cannot be corrected because
    the Encounter software cannot move the cells out of the group.
    So take care of each effective module target utilization (TU=%) value to represent their physical design .
    Not an AE .


    Originally posted in cdnusers.org by mohanch007
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Started by archive at 22 Mar 2006 06:03 AM. Topic has 5 replies.