Callback function or similar method to update simulation data before rendering images

[benjaminjeliot]

Hi everyone,

Is there a way I can use a callback or similar, to update simulation data before rendering images?

I am using Ascent with a simulation which has a relatively-expensive data-update method that I call before publishing the data to Ascent. This data-update method is only needed if I am going to be rendering images, otherwise it is wasted effort. When using ascent_actions.yaml file with triggers, I may end up with many timesteps where I don't need to render any simulation data.

Is there a way that I can call a "data_update" method only when needed, through a callback or similar mechanism? Ideally only when the trigger condition is met.

Many thanks,
Jim

[cyrush]

@benjaminjeliot do you need a partial update for the trigger, and then a full update to render?

You can register callbacks that call your own custom code:

https://github.com/Alpine-DAV/ascent/blob/develop/src/tests/ascent/t_ascent_commands.cpp

With this, you could create a callback, that is invoked by a trigger. Then the call does the full publish to another ascent instance and executes full rendering.

[benjaminjeliot]

Thanks @cyrush for your reply.

Using the CloverLeaf 3D example in the Ascent proxies directory, as an example . In the visit subroutine where Ascent is called, there is a call to viscosity:

https://github.com/Alpine-DAV/ascent/blob/develop/src/examples/proxies/cloverleaf3d-ref/visit.F90#L96

The viscosity subroutine is invoked to make sure the data is up to date with the current energy, density, and velocity. I think that this is only required if Ascent is going to render some images. With my current setup, I would have to do a call to viscosity every timestep, just in case the Ascent trigger needs the data, which might be wasted effort. I would like to be able to only call viscosity when the trigger evaluates to true.

Similarly, for applications where I am passing a matset to Ascent, I would probably have to reformat the matset data to be in a format compatible with Conduit. I want to only pay the cost of reformatting my data if I am going to create a plot.

So with the viscosity case, I can publish the mesh to Ascent, as well as the pointers for my data. I would then like the trigger to call viscosity to update the data before creating images.

In the matset case, I can publish the mesh to Ascent, but I want to delay passing a pointer to the matset data, until the trigger evaluates true. I would need something like:

• a way to pass a getter function to Conduit instead of a pointer to the data
• or a callback function to add/publish the matset data depending on the trigger

I'll take a look at the example that you shared for registering callbacks.

Thanks for your help.

Kind regards,
Jim

[benjaminjeliot]

Hi @cyrush

I have added some callbacks into my Ascent proxy app, but I can't quite get it to work:

Here is my ascent_actions.yaml:

-
  action: "add_triggers"

  triggers:

    t0:
      params:
        condition: "cycle() % 10 == 0"
        actions_file: "ascent_trigger_actions.yaml"

and here is the ascent_trigger_actions.yaml file:

-
  action: "add_triggers"

  triggers:

    t0:
      params:
        callback: "bool_callback_1"
        actions_file: bool_callback_1_actions.yaml

and finally here is the bool_callback_1_actions.yaml file:

-
  action: "add_scenes"

  scenes:

    # This plot is working
    s0:
      plots:
        p0:
          type: "pseudocolor"
          field: "field_1"
      renders:
        r0:
          image_width: 1024
          image_height: 512
          image_prefix: "field_1_%04d"

    # This plot is not working
    s1:
      plots:
        p0:
          type: "pseudocolor"
          field: "field_2"
      renders:
        r0:
          image_width: 1024
          image_height: 512
          image_prefix: "field_2_%04d"

I have created the bool_callback_1 function, and registered it with Ascent using ascent::register_callback.
The bool_callback_1 function is being called.

In my example I am adding field_1 in the original ascent::publish.
The bit that I can't figure out is how to add field_2 in the bool_callback_1 function.
Do I need to call ascent::publish and ascent::execute in the callback function?

Am I on the right track? How can I add extra fields in the callback function?

Kind regards,
Jim

[cyrush]

@benjaminjeliot yes, you should try a separate instance of ascent , publish and exec in your callback function.

[benjaminjeliot]

Thanks @cyrush, that makes sense.

I can now create a new Ascent instance, and publish my data in the bool_callback_1 function.
Though I'm still not sure how to get to the actions data, that I need to pass to the execute function.

If I use a callback like in my ascent_trigger_actions.yaml above:

-
  action: "add_triggers"

  triggers:

    t0:
      params:
        callback: "bool_callback_1"
        actions_file: bool_callback_1_actions.yaml

How can I get access to the actions data from the actions_file parameter, from inside the bool_callback_1 function?

Is there a way to get the actions_file parameter? Or is there a way to access the actions data as a Conduit node? Or am I approaching this in the wrong way?

Many thanks,
Jim