Swap Instances in a layout (based on existing topcell reference or external one by gds read)

Comments

• ahafid

  September 2013 edited September 2013

  For information, i've just found this topic on the forum: http://klayout.de/forum/comments.php?DiscussionID=5&page=1#Item_1
  
  It answers partially, and i can do what i wanted through GUI as explained in the message. But i'm unable to find how to change the parameter "reference" for an instance.
  
  No method in the "instance" or "cell" classes helped me, i suppose i can obtain a pointer on a specific instance and access to the parameter "reference"...
  
  How can i script this, i'm little lost.
  
  Best regards.
  
  Ha
• Matthias

  September 2013 edited September 2013

  Hi Ha,

  well, renaming a cell does what it's supposed to ... It changes the name of the cell. Instances are not made by name, they are made by cell index.

  If you want to make instances point to another cell, you have to use code like this

  layout_cell = ... # Cell object of the cell where you want to replace the instances
  prev_cell_index = ... # Cell index of the previous cell (i.e. index of "AN2D0")
  new_cell_index = ... # Cell index of the new cell (i.e. index of "AN2D0_V1")
  
  layout_cell.each_inst do |inst|   # gives Instance objects
    if inst.cell_index == prev_cell_index
      cell_inst_object = inst.cell_inst.dup         # gives a CellInstArray object which you can modify
      cell_inst_object.cell_index = new_cell_index  # change the reference
      inst.cell_inst = cell_inst_object             # replace the instance
    end
  end
  

  In the next version, you'll be able to simply modify the Instance object delivered by each_instances, i.e. inst.cell_index = new_cell_index.

  Allow me one more note: if you load a layout into another to merge the contents of both layouts, you need to make sure, the layouts to not contain cells with the same name or the reader will merge the contents of both cells. That is also true for child cells, so if you load a layout called "AN2D0_V1" in the forth step of your flow and this layout contains a child cell called "VIA", it will be merged with and other cell called "VIA" in the original layout with potential side effects.

  To avoid that, you can load the new cell into a separate layout and copy over the cell into the original layout (code for that see http://klayout.de/forum/comments.php?DiscussionID=103&page=1#Item_10 for example). That also gives you a chance to check for identical database units for example.

  Matthias
• ahafid

  September 2013 edited November -1

  Hi Matthias,
  
  Thanks a lot for yourt quick answer,it will be helpful, i'll fix my code following your advises and i think i've enough inforfomations now to succeed.
  
  Have a good day and congratulations for your job, klayout is a great app.
  
  Best Regards,
  
  Ha.
• Canny

  April 2015 edited November -1

  Hi, Matthias,
  
  I'm a little confused with the definition between "cell" and "instance" in klayout.
  Is there any reference to explain it?
  I can't understand why it is instance replaced in this example.
  Thank you.
  
  Regards,
  Canny
• davidnhutch

  April 2015 edited April 2015

  I know I'm not Matthias :-) But just trying to make his job easier, as he has given us great software and it is the least I can do to return the favor..

  Cell is a regular GDS 'cell', that is: it is sort of a container that holds shapes and other instances.

  Instance is an instance of that cell. So, it is a cell with some associated information (which parent cell it is to be found inside, which xy translation inside that parent, whether it is rotated or mirrored, ...)

  So, you may have this hierarchy in the hierarchy tree on the left of KL's main window: (CAPS names refer to cell names)

  TOPCELL
    CHILD1
      GRANDCHILD1
    CHILD2
      GRANDCHILD1
      GRANDCHILD2
    CHILD3
      GRANDCHILD1
      GRANDCHILD2
      GRANDCHILD3
  

  Even though "GRANDCHILD1" shows up three times in the list, it is just one cell (but instanced under three different parent cells, perhaps instanced differently (different xy location, different rotation/mirroring) in each CHILDx)

  If unclear, or if I answered what was not your question, feel free to reply

  David
• Canny

  April 2015 edited November -1

  Hi, David,
  
  Thanks, I get the clear image from the reply.
  And I kown why it uses instance replace in this example.
  
  I'd appreciate your explanation.
  
  Regards,
  Canny
• Matthias

  May 2015 edited November -1

  Hi David,

  many thanks for taking care of this and me :-)

  Matthias