NonlinearPDE Class: Sympy not installed, AttributeError and TypeError

[n1ck94]

Not sure if it is meant to or not but Sympy isn't being installed when installing escript via conda install -c conda-forge esys-escript. So upon attempting to solve a PDE with the NonlinearPDE class the following RuntimeError is raised:

RuntimeError: Trying to instantiate a Symbol but sympy not available

this is easily fixed by installing Sympy however.

Running the following code

from esys.escript import * from esys.finley import Rectangle from esys.weipa import saveSilo dom = Rectangle(l0=1.,l1=1.,n0=100, n1=100) y=dom.getX()[1] u = Symbol('u',(), dim=2) X = Symbol('X',(2,), dim=2)#setting the shape to (2,) makes X a vector phi = 1 + y*2 h=1 + y X[0]=0 X[1]=grad(u)[1]phi Y = yu # this is the Non linear functionf from the pde Y1 = hgrad(u)[1]-Y #this is the onle that we put into the non linear pde class print(Y1) p = NonlinearPDE(dom, u, debug=NonlinearPDE.DEBUG0) gammaD=whereZero(y) p.setValue(X=X,q=gammaD,Y=Y1,r=1) v = p.getSolution(u=0)

which was extracted from LaunchPad question 256021 (nonlinear pde with nonconstant coefficients) raises the following AttributeError:

AttributeError: 'list' object has no attribute 'is_Float'

Running the 'plain_strain.py' example script from the escript user guide raises the following IndexError

IndexError: too many indices for array: array is 0-dimensional, but 2 were indexed

Not sure of a fix/work around for the AttributeError and IndexError so any assistance is appreciated.

[esys-escript]

@n1ck94 which version of sympy is installed in your conda environment?

[n1ck94]

Sympy version 1.6.2

[esys-escript]

@n1ck94 unforunately, escript only supports sympy version 1.1 and lower. Could you please try installing sympy version 1.1 in your conda environment and see if this resolves your error?

[n1ck94]

Ok thanks. The conda specifications indicate that escript requires python versions 2.7 or 3.8 but sympy version 1.1 is only compatible with python version <3.8. Leaving only python version 2.7. Is this correct? I'm currently trying to install escript via conda in a python 2.7 environment but it's getting stuck on "Solving Environment". Is it only for later python versions that escript can be installed via conda?

[n1ck94]

With python version 2.7.18, sympy version 1.1.1 and escript version 5.4 I'm still getting the IndexError as I mentioned above when I run the plain_strain.py example script (copied below):

from esys.escript import *
from esys.finley import Rectangle
mydomain = Rectangle(l0=1.,l1=1.,n0=10, n1=10)
u = Symbol('u',(2,), dim=2)
q = Symbol('q', (2,2))
sigma = Symbol('sigma',(2,2))
theta = Symbol('theta')
q[0,0]=cos(theta)
q[0,1]=-sin(theta)
q[1,0]=sin(theta)
q[1,1]=cos(theta)
x = Function(mydomain).getX()
q=q.subs(theta,(3.14/4)*whereNonNegative(x[1]-.30)*whereNegative(x[1]-.70))
epsilon0 = symmetric(grad(u))
epsilon = matrixmult(matrixmult(q,epsilon0),q.transpose(1))
c00 = 10
c01 = 8; c11 = 10
c05 = 0; c15 = 0; c55 = 1
sigma[0,0] = c00*epsilon[0,0]+c01*epsilon[1,1]+c05*2*epsilon[1,0]
sigma[1,1] = c01*epsilon[0,0]+c11*epsilon[1,1]+c15*2*epsilon[1,0]
sigma[0,1] = c05*epsilon[0,0]+c15*epsilon[1,1]+c55*2*epsilon[1,0]
sigma[1,0] = sigma[0,1]
sigma0=matrixmult(matrixmult(q.transpose(1),sigma),q)
x=mydomain.getX()
gammaD=whereZero(x[1])*[1,1]
yconstraint = FunctionOnBoundary(mydomain).getX()[1]
p = NonlinearPDE(mydomain, u, debug=NonlinearPDE.DEBUG0)
p.setValue(X=sigma0,q=gammaD,y=[-50,0]*whereZero(yconstraint-1),r=[1,1])
v = p.getSolution(u=[0,0])

The error output is as follows:

Traceback (most recent call last):
  File "esNLTest.py", line 19, in <module>
    q=q.subs(theta,(3.14/4)*whereNonNegative(x[1]-.30)*whereNegative(x[1]-.70))
  File "escriptcore/py_src/symbolic/symbol.py", line 412, in subs
IndexError: too many indices for array

Are the package version I have installed correct? Thanks.