[c++] Fix fast path for SparseNDArray nnz
#6691
| Job | Run time |
|---|---|
| 22m 56s | |
| 5m 18s | |
| 15m 11s | |
| 43m 25s |
SparseNDArray nnz
#6691
| Job | Run time |
|---|---|
| 22m 56s | |
| 5m 18s | |
| 15m 11s | |
| 43m 25s |