Error at simple 1D poisson Problem

[Vicente Gomez Herrera (Guest Researcher)]

I'm trying to implement a Linear Boundary Value problems solver, but there's a weird error coming up, not sure what's going wrong

import numpy as np
import matplotlib.pyplot as plt
import dedalus.public as d3
import logging
logger = logging.getLogger(__name__)


# Parameters
N = 32


# Basis
coord = d3.Coordinate('x')
dist = d3.Distributor(coord, dtype=np.complex128)
basis = d3.ChebyshevT(coord, N, bounds=(-1, 1))

# Fields
u = dist.Field(bases=basis)
tau_1 = dist.Field(name='tau_1', bases=basis)
tau_2 = dist.Field(name='tau_2', bases=basis)

# Substitutions
x = dist.local_grid(basis)

f = dist.Field(bases = basis)
f['g'] = 1 + 0*x

dx = lambda A: d3.Differentiate(A, coord)
lift_basis = basis.derivative_basis(2)
lift = lambda A, n: d3.Lift(A, lift_basis, n)

problem = d3.LBVP([u,tau_1, tau_2],  namespace=locals())
problem.add_equation("dx(dx(u)) +  lift(tau_1,-1) + lift(tau_2,-2) = f")
problem.add_equation("u(x=-1)=0")
problem.add_equation("u(x=1)=0")

solver = problem.build_solver()
solver.solve()

Seems that the lift function is having an issue, specifically I get the error:

Traceback (most recent call last):

  File "/Users/vgomezherrera/Downloads/dedalus_poisson_try.py", line 33, in <module>

    problem.add_equation("dx(dx(u)) +  lift(tau_1,-1) + lift(tau_2,-2) = f")

  File "/Users/vgomezherrera/opt/anaconda3/envs/dedalus3/lib/python3.11/site-packages/dedalus/core/problems.py", line 72, in add_equation

    LHS = eval(LHS_str, namespace)

          ^^^^^^^^^^^^^^^^^^^^^^^^

  File "<string>", line 1, in <module>

  File "/Users/vgomezherrera/Downloads/dedalus_poisson_try.py", line 30, in <lambda>

    lift = lambda A, n: d3.Lift(A, lift_basis, n)

                        ^^^^^^^^^^^^^^^^^^^^^^^^^

  File "/Users/vgomezherrera/opt/anaconda3/envs/dedalus3/lib/python3.11/site-packages/dedalus/tools/dispatch.py", line 35, in __call__

    raise NotImplementedError("No subclasses of {} found for the supplied arguments: {}, {}".format(cls, args, kw))

NotImplementedError: No subclasses of <class 'dedalus.core.operators.Lift'> found for the supplied arguments: (<Field 4802393104>, <dedalus.core.basis.Jacobi object at 0x120a9a4d0>, -1), {'out': None}

[Jeffrey S. Oishi]

Hi,

In 1-D, the taus are just scalar values, so they should not have bases attached to them.

Substitute

tau_1 = dist.Field(name='tau_1')
tau_2 = dist.Field(name='tau_2')

in your code, and it should run.

Jeff

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