Energy classroom exercise

[mattagape]

1. likelyhood should be likelihood

2. The text says "Given a vector n of positive integers, and of arbitrary length" <-- what do these integers represent? Number of particles at each position (vector index)? (we have to look at the code to see what he means)

3. The starting point is given as: def energy(density, coeff=1.0): But I don't think coefficient is used anywhere. It isn't defined properly either. It made me look ahead to the solution to see what it was used for (it wasn't).

4. Not sure what the point of def test_derivative(): is. I understand d(n^2-1)/dn = 2n but why are we doing this at all?

5. Test coverage. When I ran it I got:

   
   eduroam-int-dhcp-97-231-100:diffusion matthewgillman$ py.test --cov
   ================================================= test session starts =================================================
   platform darwin -- Python 3.6.5, pytest-3.5.1, py-1.5.3, pluggy-0.6.0
   rootdir: /Users/matthewgillman/Desktop/MPHYG001/rsd-engineeringcourse/diffusion, inifile:
   plugins: remotedata-0.2.1, openfiles-0.3.0, doctestplus-0.1.3, cov-2.5.1, arraydiff-0.2
   collected 6 items                                                                                                     

test_model.py ...... [100%]

---------- coverage: platform darwin, python 3.6.5-final-0 ----------- Name Stmts Miss Cover

init.py 0 0 100% model.py 10 0 100% test_model.py 32 0 100%

TOTAL 42 0 100%

============================================== 6 passed in 0.03 seconds ===============================================

I didn't get all the extra output in the notes.

[ageorgou]

• The description is literally synonymous to the title! Should we add some more text?
• Starting point:
  • Thecoeff parameter is neither explained nor used again in the solution
  • Maybe say that we will look at and explain the __init__.py file and .model syntax in a future lesson (packaging)
  • It may be useful to give some hints of things they could/should test, e.g. that the input is correct, that we get the correct result in a sample case, ... Otherwise it seems too open-ended and it may be hard to start.
  • In particular, the last two tests (checking the difference in energy if the count is increased by one) make no sense without some more explanation of why we might want them.
• Solution:
  • Error message under if density.ndim != 1:: extra "an"
  • test_energy_fails_on_negative_density: fix formatting (energy should be under with ...)
  • and the same in the next test
  • test_derivative: I don't see what the d.../dn expression contributes, or where it comes from
  • test_derivative (again): The 2 * [...] if [...] > 0 else 0 isn't needed, since the numbers will be non-negative and the result for 0 will be the same either way

[dpshelio]

• [ ] (3) remove coeff.