# ValueError: Symmetric part of tensor with rank != 2 is undefined **URL:** \ **Category:** General\ **Created:** [August 21, 2024, 8:30pm UTC](https://fenicsproject.discourse.group/t/valueerror-symmetric-part-of-tensor-with-rank-2-is-undefined/15602 "2024-08-21T20:30:47Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![prusso630](https://avatars.discourse-cdn.com/v4/letter/p/ba9def/32.png) [@prusso630](https://fenicsproject.discourse.group/u/prusso630)\ **Post date:** [August 21, 2024, 8:30pm UTC](https://fenicsproject.discourse.group/t/valueerror-symmetric-part-of-tensor-with-rank-2-is-undefined/15602/1 "2024-08-21T20:30:47Z")
```auto import numpy as np from mpi4py import MPI import ufl from dolfinx import fem, mesh import dolfinx.fem.petsc L = 120.0 W = 4.0 H = 8.0 Nx = 20 Ny = 5 Nz = 10 domain = mesh.create_box( MPI.COMM_WORLD, [(0.0, 0.0, 0.0), (L, W, H)], (Nx, Ny, Nz), cell_type=mesh.CellType.hexahedron ) E = fem.Constant(domain, 2000000.0) nu = fem.Constant(domain, 0.3) mu = E / 2 / (1 + nu) lmbda = E * nu / (1 + nu) / (1 - 2 * nu) def eps(v): return ufl.sym(ufl.grad(v)) def sigma(v): return lmbda * ufl.tr(eps(v)) * ufl.Identity(3) + 2.0 * mu * eps(v) fx = 0.1 fy = -1.0 f = fem.Constant(domain, (fx, fy)) V = fem.functionspace(domain, ("Lagrange", 1)) du = ufl.TrialFunction(V) u_ = ufl.TestFunction(V) a = ufl.inner(sigma(du), eps(u_)) * ufl.dx l = ufl.inner(f, u_) * ufl.dx ``` I modified the code from the computing reactions example where a 2D cantilever beam is set up and changed things over to a box because I would like to experiment a bit with how to take moment from a 3D mesh. This code also was modified in the hopes to create a stress tensor that can work with the 3D box: ```auto def sigma(v): return lmbda * ufl.tr(eps(v)) * ufl.Identity(3) + 2.0 * mu * eps(v) ``` So there seems to be a difficulty creating the bilinear form a… ```auto Traceback (most recent call last): File "/home/prusso/dolfinx-demos/Untitled-1", line 40, in a = ufl.inner(sigma(du), eps(u_)) * ufl.dx ^^^^^^^^^ File "/home/prusso/dolfinx-demos/Untitled-1", line 31, in sigma return lmbda * ufl.tr(eps(v)) * ufl.Identity(3) + 2.0 * mu * eps(v) ^^^^^^ File "/home/prusso/dolfinx-demos/Untitled-1", line 27, in eps return ufl.sym(ufl.grad(v)) ^^^^^^^^^^^^^^^^^^^^ File "/home/prusso/spack/var/spack/environments/fenicsx-env/.spack-env/view/lib/python3.11/site-packages/ufl/operators.py", line 337, in sym return Sym(A) ^^^^^^ File "/home/prusso/spack/var/spack/environments/fenicsx-env/.spack-env/view/lib/python3.11/site-packages/ufl/tensoralgebra.py", line 542, in __new__ raise ValueError("Symmetric part of tensor with rank != 2 is undefined.") ValueError: Symmetric part of tensor with rank != 2 is undefined. ``` I don’t really know what it means at this point. How should the code be set up in terms of finding the post processed stress for in terms of moment or Mz for the box? ---
**Author:** ![francesco-ballarin](https://avatars.discourse-cdn.com/v4/letter/f/f05b48/32.png) [@francesco-ballarin](https://fenicsproject.discourse.group/u/francesco-ballarin)\ **Post date:** [August 22, 2024, 5:16am UTC](https://fenicsproject.discourse.group/t/valueerror-symmetric-part-of-tensor-with-rank-2-is-undefined/15602/2 "2024-08-22T05:16:24Z")
> [@prusso630](#): > > ```auto > V = fem.functionspace(domain, ("Lagrange", 1)) > > ``` This generates a FE space for a scalar field. If you want a vector field you have to use ```auto V = fem.functionspace(domain, ("Lagrange", 1, (3, ))) ``` or ```auto V = fem.functionspace(domain, ("Lagrange", 1, (domain.topology.dim, ))) ``` ---
**Author:** ![prusso630](https://avatars.discourse-cdn.com/v4/letter/p/ba9def/32.png) [@prusso630](https://fenicsproject.discourse.group/u/prusso630)\ **Post date:** [August 22, 2024, 5:31am UTC](https://fenicsproject.discourse.group/t/valueerror-symmetric-part-of-tensor-with-rank-2-is-undefined/15602/3 "2024-08-22T05:31:20Z")
If I change only these lines to: ```auto f = fem.Constant(domain, (fx, fy, 0.0)) V = fem.functionspace(domain, ("Lagrange", 1), (3, )) ``` There will be a traceback: ```auto Traceback (most recent call last): File "/home/prusso/dolfinx-demos/Untitled-1.py", line 37, in V = fem.functionspace(domain, ("Lagrange", 1), (3, )) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/home/prusso/spack/var/spack/environments/fenicsx-env/.spack-env/view/lib/python3.11/site-packages/dolfinx/fem/function.py", line 654, in functionspace form_compiler_options["scalar_type"] = dtype ~~~~~~~~~~~~~~~~~~~~~ ^^^^^^^^^^^^^^^ TypeError: 'tuple' object does not support item assignment ``` A tuples item is being assigned somehow in a way that is throwing exception. Some information about a scalar\_type is given. Beyond that I really am not sure yet what to make of it… ---
**Author:** ![francesco-ballarin](https://avatars.discourse-cdn.com/v4/letter/f/f05b48/32.png) [@francesco-ballarin](https://fenicsproject.discourse.group/u/francesco-ballarin)\ **Post date:** [August 22, 2024, 6:01am UTC](https://fenicsproject.discourse.group/t/valueerror-symmetric-part-of-tensor-with-rank-2-is-undefined/15602/4 "2024-08-22T06:01:06Z")
Sorry, I was going by heart and messed up the syntax. I am editing now the post with the correct syntax. ---
**Author:** ![dokken](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/dokken/32/1560_2.png) [@dokken](https://fenicsproject.discourse.group/u/dokken)\ **Post date:** [August 22, 2024, 3:02pm UTC](https://fenicsproject.discourse.group/t/valueerror-symmetric-part-of-tensor-with-rank-2-is-undefined/15602/5 "2024-08-22T15:02:31Z")
> [@francesco-ballarin](#): > > `V = fem.functionspace(domain, ("Lagrange", 1, (domain.topology.dim, )))` This should probably be `V = fem.functionspace(domain, ("Lagrange", 1, (domain.geometry.dim, )))` if you want the space to be compatible with a `ufl.grad` object on a potential manifold:)