Add slack histogram to the GUI

[maliberty]

Description

Add a histogram of endpoint slack to the GUI

Suggested Solution

https://doc.qt.io/qt-5/qtcharts-barchart-example.html looks like a good starting point

Additional Context

No response

[QuantamHD]

@maliberty Do you have an example of the format of such a chart?

[QuantamHD]

I found this example online.

[maliberty]

That's what I'm thinking of. Having a generic histogram capability would be useful for many things (fanout, congestion, etc).

[Sov-trotter]

Hey All. First time contributor here! Would love to work on this issue. :)

[QuantamHD]

That's great!

The gui code is located here. https://github.com/The-OpenROAD-Project/OpenROAD/tree/master/src/gui

[maliberty]

Feel free to ask questions. @gadfort and I can help

[Sov-trotter]

Hey. I've been able to get a general layout done.

Looking at the TimingWidget code I am not able to figure out where to get the data (number of paths and the slack). I assume that it's basic preprocessing before plotting, or do I need something like a TimingModel?

[gadfort]

You will likely need to use: https://github.com/The-OpenROAD-Project/OpenROAD/blob/bb4801b7457d04f2ddf27c202803dfbe5c8f324d/src/gui/src/staGuiInterface.cpp#L724 At the moment it's configured to return more than one path per endpoint. This is something relatively easy (I assume) to modify and I'm happy to do that if you want. Another thing to consider adding are controls for setup and hold slacks and corners (although those would be easy to get in once the widget is functional.

In the TimingPath class (which is what the getTimingPaths returns a list of) you should just be able to call getSlack for the slack on that path. I hope this helps.

[Sov-trotter]

At the moment it's configured to return more than one path per endpoint.

Thanks for adding this.

Another thing to consider adding are controls for setup and hold slacks and corners (although those would be easy to get in once the widget is functional.

Sure. This is my first time with Qt, so learning as I go along. :)

[maliberty]

Just checking in - are you able to make progress? Do you need any further help?

[Sov-trotter]

I am not quite able to wrap my head around the general flow. One specific question I have is Is getTimingPaths supposed to run after populatePaths/ updating?

I am not sure if I am getting the data in the right way to pass into the bar chart set.

[maliberty]

@gadfort would you help with this question.

[gadfort]

@Sov-trotter you should be using the STAGuiInterface class for your widget. All you need to do it call getTimingPaths() and that should give you all the paths. You question about populatePaths makes we think you are attempting to integrate into the timing widget (@maliberty I'm not sure this was the intent, but please clarify).

Also if you have a fork of OpenROAD you can always point us to it so we can better help with particular issues.

[Sov-trotter]

No I am not trying to integrate it into the timing widget. Working on a fork might be a good idea. I'll create one in sometime and let you know.

[Sov-trotter]

Hey. I am not quite able to figure out what pin should be the input parameter to getTimingPaths(). I looked around the code but couldn't find what is the appropriate from, thru or to value to get all the timing paths. Any pointers would be helpful. Thanks

[gadfort]

I don't think you need to supply any pins, you can call the function without any of those parameters and you will get all timing paths.

[maliberty]

I'm getting a bit confused. The slack histogram should show slack at timing end points (ie registers, macros, etc). Why do we need timing paths?

[gadfort]

@maliberty we don't technically need the timing paths (it's just the helper function is there and can be used without generating new helper functions). What we need is a single timing path for each endpoint (which the function can generate) and then we just need to mark the slack on the path (which the TimingPath has collected).

[maliberty]

Sta::vertexSlack is faster than getting a path.

[maliberty]

What does "mark the slack on the path" mean?

[gadfort]

The slack is set in the TimingPath object. Yes, you are right about the verterxSlack being faster, I figured that is something we could add to the STA GUI interface in the future, and modify this to use it. Ultimately it's the same information.

[maliberty]

I'm ok with two steps to get there. I think it will matter on large designs but it can wait for a follow on.

[maliberty]

@Sov-trotter how is it going with this? Do you have any code you can share?

[Sov-trotter]

Sorry for the late reply. I haven't been able to find time to work on this lately. I can't seem to fully wrap my head around the Qt API either.

[maliberty]

If you put your work in a public area perhaps someone can help move it forward. If there are specific questions about Qt I can try to answer.

[Sov-trotter]

Hmm in understand. But I won't be able to do much in the limited time I have these days. Thanks for letting me try :)

[QuantamHD]

@Sov-trotter I think it would be helpful for someone else to build on your code rather than starting over. Would it be possible to push what you have for those purposes?

[niv280]

Hi @Sov-trotter , I will be happy to continue work on it. Can you please share your progress so far?

[Sov-trotter]

Yes sure. Till now I was pretty much at the Qt charts docs step.

[AcKoucher]

Hi Everyone! I've been working on this issue for more than a month, I'm a new contributor and it's helping me a lot to get to know openroad's structure. I apologize not keeping up with this thread. I have been in contact with @maliberty since I started. So, @niv280 would you mind letting me keep working on this? By the way, my general layouy looks like this:

[niv280]

Hi, Sure, I didn't started to work on this yet. The layout looks good, looking forward to see the full feature.

[maliberty]

I don't think we should use getTimingPaths to get end point slacks. I think we should add these apis:

StaPins STAGuiInterface::getEndPoints() const
{
  StaPins pins;
  for (auto end : *sta_->endpoints()) {
    pins.insert(end->pin());
  }
  return pins;
}

float STAGuiInterface::getPinSlack(const sta::Pin* pin) const
{
  return sta_->pinSlack(pin,
                        use_max_ ? sta::MinMax::max() : sta::MinMax::min());
}

[AcKoucher]

@maliberty that makes it clearer. Thank you for the apis' code. I'll test it.