MG Tests are Failing due to Neighbor Sampling Bug

[alexbarghi-nv]

Currently, the fix is not to use -1 in the MG tests, but this is not a permanent fix. The new primitive added in #2623 should resolve this issue once it is implemented @seunghwak . Once that happens, the tests should changed back to using -1.

MRE:

import cugraph

import cudf
import dask_cudf
import cupy

import dask

from dask.distributed import Client
from dask_cuda import LocalCUDACluster
from cugraph.experimental import MGPropertyGraph
import cugraph.dask.comms.comms as Comms

if __name__ == '__main__':
    # begin test
    dask.config.set({'temporary_directory': './dask_tmp'})

    cluster = LocalCUDACluster(
                n_workers=3,
                rmm_managed_memory=False
    )
    
    client = Client(cluster)

    Comms.initialize(p2p=True)

    ddf = dask_cudf.from_cudf(
            cudf.DataFrame({
                'src': cupy.array([
                    0,
                    0,
                    1,
                    2,
                    2,
                    3
                ], dtype='int32'),
                'dst': cupy.array([
                    1,
                    2,
                    4,
                    3,
                    4,
                    1
                ], dtype='int32')
            }),
            npartitions=3
    )

    G = cugraph.Graph(directed=True)
    G.from_dask_cudf_edgelist(ddf, source='src', destination='dst', legacy_renum_only=True)

    sampling_results = cugraph.dask.uniform_neighbor_sample(
        G,
        cudf.Series([0, 1, 2, 3, 4], dtype='int32'),
        [-1],
        with_replacement=True
    )

    print(sampling_results.compute())
    Comms.destroy()

Expected:

   sources  destinations  indices
0        0             1      1.0
1        1             4      1.0
2        2             4      1.0
3        3             1      1.0
0        0             2      1.0
1        2             3      1.0

Actual:

   sources  destinations        indices
0        0             0   0.000000e+00
1        0             1   0.000000e+00
2        0             1   1.000000e+00
3        0             3   0.000000e+00
4        1             4   1.000000e+00
0        0             0 -2.121996e-314
1        0             4  3.969731e-314
2        0             2   1.000000e+00