# What is problem?

**URL:** <https://fenicsproject.discourse.group/t/what-is-problem/13992>\
**Category:** mesh\
**Tags:** gmsh\
**Created:** [March 22, 2024, 10:46am UTC](https://fenicsproject.discourse.group/t/what-is-problem/13992 "2024-03-22T10:46:15Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![lllpp](https://avatars.discourse-cdn.com/v4/letter/l/ee7513/32.png) [@lllpp](https://fenicsproject.discourse.group/u/lllpp)\
**Post date:** [March 22, 2024, 10:46am UTC](https://fenicsproject.discourse.group/t/what-is-problem/13992/1 "2024-03-22T10:46:15Z")

</div>

this is my code ,but an error is  
cell = cpp.geometry.compute\_colliding\_cells(mesh, cell\_candidates, x)  
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  
TypeError: compute\_colliding\_cells(): incompatible function arguments.

x\_r = Function(W)  
xr.copy(x\_r.vector)  
x\_i = Function(W)  
xi.copy(x\_i.vector)

xt\_r, xz\_r = x\_r.split()  
xt\_i, xz\_i = x\_i.split()

print(xt\_r.vector.array.shape)  
print(xz\_r.vector.array.shape)  
x0 = [0, 0, 0]  
xs = np.array([[x, x, 0] for x in np.linspace(0, 10, 100000)])

tree = geometry.bb\_tree(mesh,mesh.geometry.dim)  
print(‘tree’,type(tree))

e\_ts =   
e\_zs =   
rs = (xs[:, 0]\*\*2 + xs[:, 1]\*\*2)\*\*0.5

for x in xs:  
print(‘xxx’,type(x))  
print(‘xxx’,x.dtype)

```
cell_candidates = geometry.compute_collisions_points(tree, x)
print(type(mesh))
print(type(cell_candidates))
print(type(x))
print(x.dtype)

#cell = cpp.geometry.compute_colliding_cells(mesh, cell_candidates, x, 1)
cell = cpp.geometry.compute_colliding_cells(mesh, cell_candidates, x)
e_t = xt_r.eval(x, cell)
e_t_abs = np.sqrt(np.sum(e_t*np.conj(e_t))).real
e_ts.append(e_t_abs)
e_zs.append(np.absolute(xz_r.eval(x, cell)))

```

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<div class="post-metadata">

**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:** [March 22, 2024, 11:59am UTC](https://fenicsproject.discourse.group/t/what-is-problem/13992/2 "2024-03-22T11:59:48Z")

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Please provide a minimal reproducible example, and ensure that the code is formatted with 3x` encapsulation, i.e.

````python
```python
# Add code here
```

````

````bash
```bash
Add full error message with trace here
```

````

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<div class="post-metadata">

**Author:** ![lllpp](https://avatars.discourse-cdn.com/v4/letter/l/ee7513/32.png) [@lllpp](https://fenicsproject.discourse.group/u/lllpp)\
**Post date:** [March 23, 2024, 1:11am UTC](https://fenicsproject.discourse.group/t/what-is-problem/13992/3 "2024-03-23T01:11:39Z")

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I am my first logged to this forum ,what is format with 3x ?

tree = geometry.BoundingBoxTree(mesh, mesh.geometry.dim)  
cell\_candidates = geometry.compute\_collisions\_point(tree, x)  
cell = cpp.geometry.select\_colliding\_cells(mesh, cell\_candidates, x, 1)

for the code above,  
why does it always show that the input parameter type does not match .

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<div class="post-metadata">

**Author:** ![AIJAZ\_NAZIR](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/aijaz_nazir/32/5690_2.png) [@AIJAZ\_NAZIR](https://fenicsproject.discourse.group/u/AIJAZ_NAZIR)\
**Post date:** [March 23, 2024, 4:17am UTC](https://fenicsproject.discourse.group/t/what-is-problem/13992/4 "2024-03-23T04:17:11Z")

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“3x” refers to shorthand for " **three backticks**" i.e., this symbol on keyboard ```````````````````, I have exaggerated the no. of backticks you just use three in the beginning and three in the end.  
like ```  
tree = geometry.BoundingBoxTree(mesh, mesh.geometry.dim)  
cell\_candidates = geometry.compute\_collisions\_point(tree, x)  
cell = cpp.geometry.select\_colliding\_cells(mesh, cell\_candidates, x, 1)

```auto

```