Time dependent PointWiseMonitor not working

Physics Simulation PhysicsNeMo-ML Model Framework Technical Support (PhysicsNeMo Only)
1

Hi,

unfortunately, I am not able to use PointWiseMonitor, when my NN also gets the time as input. I get an error message, when initializing the PointWiseMonitor:

peak_temp_monitor = PointwiseMonitor(
        geo.sample_interior(100),
        output_names=["Temperat"],
        metrics={"peak_temp": lambda var: torch.max(var["Temperat"])},
        nodes=nodes,
        requires_grad=True,
    )
    ic_domain.add_monitor(peak_temp_monitor)

###################################
could not unroll graph!
This is probably because you are asking to compute a value that is not an output of any node
####################################
invar: [x, y, sdf, area]
requested var: [Temperat]
computable var: [x, y, sdf, area, diffusion_Temperat]
####################################
Nodes in graph: 
node: Sympy Node: diffusion_Temperat
evaluate: SympyToTorch
inputs: []
derivatives: [Temperat__t, Temperat__x__x, Temperat__y__y]
outputs: [diffusion_Temperat]
optimize: False
node: Arch Node: T_net
evaluate: FullyConnectedArch
inputs: [x, y, t]
derivatives: []
outputs: [Temperat]
optimize: True
####################################

If I remove the time dependency from and use input_keys=[Key("x"), Key("y")], instead of input_keys=[Key("x"), Key("y"), Key("t")], there is no error message:

T_net = instantiate_arch(
        # input_keys=[Key("x"), Key("y"), Key("t")],
        input_keys=[Key("x"), Key("y")],
        output_keys=[Key("Temperat")],
        cfg=cfg.arch.fully_connected,
    )

Is PointWiseMonitor not applicable in case of time-dependent problems?

Below is the full code to reproduce the issue:

import torch
import numpy as np
from sympy import Symbol, Eq


import modulus.sym


from modulus.sym.hydra import instantiate_arch, ModulusConfig  # to_absolute_path, ,
from modulus.sym.key import Key
from modulus.sym.solver import Solver
from modulus.sym.domain import Domain
from modulus.sym.geometry.primitives_2d import Rectangle

from modulus.sym.eq.pdes.diffusion import Diffusion

from modulus.sym.domain.constraint import (
    PointwiseBoundaryConstraint,
    PointwiseInteriorConstraint,
)


from modulus.sym.domain.monitor import PointwiseMonitor
from modulus.sym.domain.inferencer import PointwiseInferencer

# inferencer visualization as mesh instead of cloud
from modulus.sym.utils.io.vtk import VTKUniformGrid
from modulus.sym.domain.inferencer import PointVTKInferencer

height = 1.0
width = 1.0
heat_sink_temp = 350
base_temp = 293.498


@modulus.sym.main(config_path="conf", config_name="config")
def run(cfg: ModulusConfig) -> None:
    x, y, t_symbol = Symbol("x"), Symbol("y"), Symbol("t")
    time_window_size = 1.0
    time_range = {t_symbol: (0, time_window_size)}
    rec = Rectangle((-width / 2, -height / 2), (width / 2, height / 2))

    geo = rec

    diff_eq = Diffusion(T="Temperat", D=0.1, Q=0, dim=2, time=True)

    T_net = instantiate_arch(
        # input_keys=[Key("x"), Key("y"), Key("t")],
        input_keys=[Key("x"), Key("y")],
        output_keys=[Key("Temperat")],
        cfg=cfg.arch.fully_connected,
    )

    nodes = diff_eq.make_nodes() + [T_net.make_node(name="T_net")]
    ic_domain = Domain("initial_conditions")

    # initial condition
    IC = PointwiseInteriorConstraint(
        nodes=nodes,
        geometry=geo,
        outvar={"Temperat": (0)},
        batch_size=2500,
        parameterization={t_symbol: 0.0},
    )
    ic_domain.add_constraint(IC, "IC")

    top_wall = PointwiseBoundaryConstraint(
        nodes=nodes,
        geometry=rec,
        outvar={"Temperat": (1.0)},
        batch_size=2500,
        criteria=Eq(y, height / 2),
        parameterization=time_range,
    )
    ic_domain.add_constraint(top_wall, name="top_wall")

    remaining_walls = PointwiseBoundaryConstraint(
        nodes=nodes,
        geometry=rec,
        outvar={"Temperat": (0)},
        batch_size=2500,
        criteria=y < height / 2,
        parameterization=time_range,
    )
    ic_domain.add_constraint(remaining_walls, name="walls")

    peak_temp_monitor = PointwiseMonitor(
        geo.sample_interior(100),
        output_names=["Temperat"],
        metrics={"peak_temp": lambda var: torch.max(var["Temperat"])},
        nodes=nodes,
        requires_grad=True,
    )
    ic_domain.add_monitor(peak_temp_monitor)

    # add inference data for time slices
    for i, specific_time in enumerate(np.linspace(0, time_window_size, 10)):
        vtk_obj = VTKUniformGrid(
            bounds=[[-width / 2, width / 2], [-height / 2, height / 2]],
            npoints=[128, 128],
            export_map={"T": ["Temperat"]},
        )
        grid_inference = PointVTKInferencer(
            vtk_obj=vtk_obj,
            nodes=nodes,
            input_vtk_map={"x": "x", "y": "y"},
            output_names=["Temperat"],
            requires_grad=False,
            invar={"t": np.full([128**2, 1], specific_time)},
            batch_size=1024,
        )
        ic_domain.add_inferencer(grid_inference, name="time_slice_" + str(i).zfill(4))

    slv = Solver(cfg, ic_domain)
    slv.solve()


if __name__ == "__main__":
    run()

print("finished")

I am using Docker Container modulus:24.01.