Changelog =========

Nutils is being actively developed and the API is continuously evolving. The following overview lists user facing changes as well as newly added features in inverse chronological order.

# Changes since version 5.0¶

• Fixed and fallback lengths in (namespace) expressions

The nutils.function.Namespace has two new arguments: length_<indices> and fallback_length. The former can be used to assign fixed lengths to specific indices in expressions, say index i should have length 2, which is used for verification and resolving undefined lengths. The latter is used to resolve remaining undefined lengths.

>>> ns = nutils.function.Namespace(length_i=2, fallback_length=3)
>>> ns.eval_ij('δ_ij') # using length_i
Array<2,2>
>>> ns.eval_jk('δ_jk') # using fallback_length
Array<3,3>

• Treelog update

Nutils now depends on treelog version 1.0b5, which brings improved iterators along with other enhancements. For transitional convenience the backwards incompatible changes have been backported in the nutils.log wrapper, which now emits a warning to indicate that the fallback is active. This wrapper is scheduled for deletion prior to the release of version 6.0. To update treelog to the most recent version use:

python -m pip install -U treelog

• Unit type

The new nutils.types.unit allows for the creation of a unit system for easy specification of physical quantities. Used in conjuction with nutils.cli.run() this facilitates specifying units from the command line, as well as providing a warning mechanism against incompatible units.

>>> U = types.unit.create(m=1, s=1, g=1e-3, N='kg*m/s2', Pa='N/m2')
>>> def main(length=U('2m'), F=U('5kN')):
...   topo, geom = mesh.rectilinear([numpy.linspace(0,length,10)])

$python myscript.py length=25cm # OK$ python myscript.py F=10Pa # error!
• Sample basis

Samples now provide a nutils.sample.Sample.basis(): an array that for any point in the sample evaluates to the unit vector corresponding to its index. This new underpinning of nutils.sample.Sample.asfunction() opens the way for sampled arguments, as demonstrated in the last example below:

>>> H1 = mysample.asfunction(mydata) # mysample.eval(H1) == mydata
>>> H2 = mysample.basis().dot(mydata) # mysample.eval(H2) == mydata
>>> ns.Hbasis = mysample.basis()
>>> H3 = 'Hbasis_n ?d_n' @ ns # mysample.eval(H3, d=mydata) == mydata

• Higher order gmsh geometries

Gmsh element support has been extended to include cubic and quartic meshes in 2D and quadratic meshes in 3D, and parsing the msh file is now a cacheable operation. Additionally, tetrahedra now define bezier points at any order.

• Repository location

The Nutils repository has moved to https://github.com/evalf/nutils.git. For the time being the old address is maintained by Github as an alias, but in the long term you are advised to update your remote as follows:

git remote set-url origin https://github.com/evalf/nutils.git