Due Diligence

• General:
  • title of the PR is suitable to appear in the Release Notes
• Implementation:
  • unit tests: all split configurations tested
  • unit tests: multiple dtypes tested
  • NEW unit tests: MPS tested (1 MPI process, 1 GPU)
  • benchmarks: created for new functionality
  • benchmarks: performance improved or maintained
  • documentation updated where needed

Description

Python uses __repr__ and __str__ to give textual information about objects. The intention is that __repr__ gives output for developers and __str__ gives output for users. In heat arrays, this means __repr__ tells you, for each MPI rank, what kind of data is contained in the array, while __str__ tells you the actual data.

This is all well and good but the problem is when people are using heat interactively, in which case they get the __repr__ if they just print the array, but if they are users, they want to know the data and not the local shape.
For example:

python
import heat as ht
a = ht.arange(4)
a  # prints a.__repr__()
f"{a}"  # prints a.__str__()

when doing something like this, you tend to want to know the contents of the array in both cases.

In this PR, information about the contents of the array is appended. Before you got

$ mpirun -np 2 python -c "import heat as ht; a = ht.arange(3 * 4, split=0).reshape((3, 2, 2)); print(a.__repr__())"
<DNDarray(MPI-rank: 0, Shape: (3, 2, 2), Split: 0, Local Shape: (2, 2, 2), Device: cpu:0, Dtype: int32)>
<DNDarray(MPI-rank: 1, Shape: (3, 2, 2), Split: 0, Local Shape: (1, 2, 2), Device: cpu:0, Dtype: int32)>

with the changes introduced here, you get

$ mpirun -np 2 python -c "import heat as ht; a = ht.arange(3 * 4, split=0).reshape((3, 2, 2)); print(a.__repr__())" 
DNDarray(MPI-rank: 1, Shape: (3, 2, 2), Split: 0, Local Shape: (1, 2, 2), Device: cpu:0, Dtype: int32
         [[[ 8,  9],
           [10, 11]]])
DNDarray(MPI-rank: 0, Shape: (3, 2, 2), Split: 0, Local Shape: (2, 2, 2), Device: cpu:0, Dtype: int32
         [[[0, 1],
           [2, 3]],

          [[4, 5],
           [6, 7]]])

Compare this to the __str__ output

$ mpirun -np 2 python -c "import heat as ht; a = ht.arange(3 * 4, split=0).reshape((3, 2, 2)); print(a)"           
DNDarray([[[ 0,  1],
           [ 2,  3]],

          [[ 4,  5],
           [ 6,  7]],

          [[ 8,  9],
           [10, 11]]], dtype=ht.int32, device=cpu:0, split=0)

Let me know what you think about this.

Issue/s resolved: #2018

Changes proposed:

• Print both debug information and content information in interactive sessions
• Test for correct output in __repr__ with multiple processes