[Bug]: Minor bugs regarding `IncrementalPCA()`

[LScheib]

1. There is a return error for IncrementalPCA() objects

For PCA() we can get an overview of the current variables:

>>> import heat as ht
>>> from heat.decomposition import pca
>>> pca = ht.decomposition.PCA()
>>> pca
PCA({
    "n_components": null,
    "copy": true,
    "whiten": false,
    "svd_solver": "hierarchical",
    "tol": null,
    "iterated_power": 0,
    "n_oversamples": 10,
    "power_iteration_normalizer": "qr",
    "random_state": null
})

Trying the same for IncrementalPCA() results in:

>>> import heat as ht
>>> from heat.decomposition import pca
>>> ipca = ht.decomposition.IncrementalPCA()
>>> ipca
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File ".../heat/heat/core/base.py", line 66, in __repr__
    return f"{self.__class__.__name__}({json.dumps(self.get_params(), indent=4)})"
  File ".../heat/heat/core/base.py", line 49, in get_params
    value = getattr(self, key)
AttributeError: 'IncrementalPCA' object has no attribute 'copy'

2. Possible error in unit test test_incrementalpca_truncation_happens_split1 or base functionality

Unit test fails for 16 processes (but works for 2, 4, 8).

HEAT_TEST_USE_DEVICE=cpu mpirun -n 16 python -m unittest -vf heat/decomposition/tests/test_pca.py

======================================================================
ERROR: test_incrementalpca_truncation_happens_split1 (heat.decomposition.tests.test_pca.TestIncrementalPCA)
----------------------------------------------------------------------
Traceback (most recent call last):
  File ".../heat/heat/decomposition/tests/test_pca.py", line 315, in test_incrementalpca_truncation_happens_split1
    pca.partial_fit(data1)
  File ".../heat/heat/decomposition/pca.py", line 453, in partial_fit
    U, S, mean = _isvd(
  File ".../heat/heat/core/linalg/svdtools.py", line 658, in _isvd
    new_data = new_data.resplit_(U_old.split) - U_old @ UtC
  File ".../heat/heat/core/linalg/basics.py", line 1291, in _matmul
    return matmul(self, other)
  File ".../heat/heat/core/linalg/basics.py", line 844, in matmul
    if b.lshape[-1] % nB != 0 or (kB == 1 and b.lshape[-1] != 1):
ZeroDivisionError: integer division or modulo by zero

In my implementation of the fit() method for IncrementalPCA() (see PR #2005) I treat similar cases with this check:

if shape[1] < ht.MPI_WORLD.size:
            raise ValueError(
                f"The number of columns ({shape[1]}) must be at least equal to the number of processes ({ht.MPI_WORLD.size})."
            )

Version

main (development branch)

Python version

None

PyTorch version

None

MPI version