Clip utility

richtwhite

Hi,

Great tool by the way, very fast and reliable.

I want to use the clip utility to extract a small section of the design for further analysis. When I tried this on a small design, the "clipped" design that I saved out is 200x bigger than the source gds, despite only representing about 5% of the design.

Any ideas why this is?

richtwhite

hello again,

It seems that if I flatten the hierarchy before running clip, then I see this issue. However, if I don't flatten the hierarchy then the resulting clipped gds is still bigger, but only by a fraction of a %, not 200x.

Is klayout saving the original gds + the clipped section?

regards,
Rich

Matthias

Hi Rich,

yes, you are right, by default KLayout is saving both the clip and the original.

What KLayout actually does is do create a new top cell (by default called CLIP) containing the clip. The original top cell will still exist and show the whole layout (that way, another clip can still be made). KLayout will do the clip hierarchically by creating cell variants with just the subset required. Where a cell is completely inside the clip region, the original cell is used.

In the cell tree you will find the clip cell and the original one. Both are top cells, i.e. appear as root level nodes in the tree.

You can save just the clip by selecting the clip cell in the cell tree and choose "Save Current Cell As" from the context menu (right mouse click). Then just this cell is saved which is usually just a fraction of the original layout.

If you want a flat clip, I would recommend to flatten just the clip cell (after the clip) using "Flatten" from the context menu. That produces a much smaller data volume as you have noticed ... :-)

Best regards,

Matthias

richtwhite

Hi Matthias,

Thanks for your help and advice, that's exactly what I needed. I was only using the "show current cell as top" not "save current cell as".

Best regards,
Rich

ackusingh

Hi
I need to modify the clip tool so that it automatically cuts the whole gds into various smaller square (of desired size) gds and save them as separate gds files. Can you please guide me on how to proceed for this ?

Matthias

Hi,

I would suggest to create a ruby script that does that - however, right now, the clip function is not provided as a ruby method and it's pretty tedious to emulate it. I'll consider that as a suggestion for the next release (which hopefully will come soon).

Right now, you would have to modify the code - the place to look for is layClipDialog.cc, around line 200. The basic function is db::clip_layout which does the work. It already provides a way to create multiple clips in separate cells. You'll need to save the cells in separate files using db::Writer (dbWriter.h) and provide a individual cell in the db::SaveLayoutOptions (method add_cell).

There is also a manual solution. The clip tool already allows to build multiple clips into separate cells. A separate cell is not the same than a separate GDS file, but maybe you flow allows to use the same file with a different top cell, so you can extract the clip from a single GDS file, provided each clip is contained in it's own cell.

The manual procedure is that: create a regular arrangement of boxes covering your layout on a new layer. I did so by creating a new cell with a single box and changing the boxes properties to (0,0) for the lower left and (100,100) for the upper right corner for example. This box now represents one clip tile. You can create a regular arrangement of boxes easily by placing a array instance of that cell over your layout: place an instance and check the "array instance" box, enter the desired box size as displacement vectors - i.e. (0,100) and (100,0).

Now your layout is prepared to be clipped into pieces. Just select the clip tool and choose "Shapes on layer .." for the clip box specification. Enter the layer that you placed the boxes on previously.

After having ran the clip tool, you will see a new cell called "CLIP" containing a sub-hierarchy of individual clips. If the original cell for called "TOP" for example, the clip cells will be called "TOP$1" for the lower left clip, "TOP$2" for the next clip right of that one and so on.

Maybe this information is helpful.

Best regards,

Matthias

ackusingh

Hi,

Thanks a lot and I tried the manual selection method, its pretty useful. I was also interested in using Klayout in a batch ( non-interactive) mode so that the cutting of gds can be done through a script. Can you suggest me ways for this ?

Regards
Acku

Matthias

Hi Acku,

With the next release (0.21) it will be possible to write a ruby script that creates the desired clips and saves them to individual GDS files using the integrated ruby interpreter (RBA).

This will be far easier than modifying the C++ code and more flexible.

This is basically how the script might look like in upcoming version 0.21:

# HINT: this simple implementation does not account 
# for variant building - the shapes and instances are simply taken
# out from the original shapes and therefore might disappear somewhere else.

$multiclip = RBA::Action.new
$multiclip.title = "Multiclip"
$multiclip.on_triggered do 

    app = RBA::Application.instance
    mw = app.main_window

    lv = mw.current_view
    if !lv || !lv.active_cellview
      raise "Multiclip: No view or no layout active"
    end

    lay = lv.active_cellview.layout
    top = lv.active_cellview.cell_index
    top_name = lay.cell_name(top)

    # Prepare a new layout to receive the clips
    cl = RBA::Layout.new
    cl.dbu = lay.dbu
    lay.layer_indices.each do |li|
      cl.insert_layer_at(li, lay.get_info(li))
    end

    # b = the top cell's bounding box
    b = lv.active_cellview.cell.bbox

    # Compute a box size and a box count in x and y direction
    s = (b.width / 10.0).ceil
    nh = (b.height / s).ceil
    nw = 10

    # Prepare the boxes and assign file names
    boxes = []
    filenames = []
    (1..nw).each do |iw|
      (1..nh).each do |ih|
        boxes.push(RBA::Box.new(b.left + s * (iw - 1), b.bottom + s * (ih - 1),
                                b.left + s * iw, b.bottom + s * ih))
        filenames.push("clip_#{iw}_#{ih}.gds")
      end
    end

    # Actually do the clip
    cells = lay.multi_clip_into(top, cl, boxes)

    # Write the cells to individual files
    cells.zip(filenames).each do |c,fn|

      # Rename the clip's top cell to the original top
      cl.rename_cell(c, top_name)

      # Save this cell and it's child cell tree
      opt = RBA::SaveLayoutOptions::new
      opt.format = "GDS2";
      opt.add_cell(c)
      cl.write(fn, false, opt)

      puts "Written #{fn} with top cell #{top_name} .."

    end

end


app = RBA::Application.instance
mw = app.main_window

menu = mw.menu
menu.insert_item("@toolbar.end", "multiclip", $multiclip)

Best regards,

Matthias

ackusingh

This sounds great !!
The code above would be very helpful to me in writing ruby scripts.
Thanks a lot

Regards

Acku

ackusingh

Hi Matthias
I saw in release notes that version 0.21.1 is out, so is the clip method now available through a ruby method ?

Matthias

Hi,

Sorry for not mentioning that here. Yes it is. I changed to code above so it is a full Ruby module. Copy the code into some file, i.e. "multiclip.rbm" and run KLayout (version 0.21.1) like this:

klayout -rm multiclip.rbm ...

If you copy multiclip.rbm to the installation folder on Windows or to a folder pointed to be $KLAYOUTPATH on Linux, it will be loaded automatically without needing the -rm option.

Please adapt the script as you require. It provides a new entry in the toolsbar called "Multiclip", which creates the clips.

For all users familiar with the RBA scheme, this script also employs a new feature (events) which simplify binding of code to actions.

Best regards,

Matthias

ackusingh

Hi

sure i'll try to do it. Probably I want to use this multi clip feature in a non interactive mode so that things could be automated. So as it is a ruby method, I can do some experiments :)

Thanks

Acku

rajan

Updating these instructions, thanks for the nice clipping utility Matthias (please correct any mistakes here).

1. With your layout to be clipped, go to "Edit -> Utilities -> Clip Tool"
2. Select the location and size of the clip (I like to use the "Box center and dimensions" option because then I can right click on the center of the clip, then "CTRL + g" to see the center and input those numbers)
3. Find your clip on the "Cells" menu, probably on the left of your KLayout window, right click on it and select "Save Selected Cells As"
4. Pick path to save new clip
5. Fill out the fields in the "Save Layout Options" window

If you have saved a small clip it should be done in less than a second.

HTH,

Rajan