[BUG] Cagra To hnsw, the search api not use search param ef

[Presburger]

We recently tried to convert CAGRA to HNSW using RAFT's built-in API. We found that the ef parameter was not passed to hnswlib. Moreover, even when using setEf to set the ef parameter, there are concurrency issues.

raft/cpp/include/raft/neighbors/hnsw.hpp

Line 122 in b66b269

const search_params& params,

[divyegala]

@Presburger thank you for bringing this up, I'll look into this.

Could you please describe the concurrency issues?

[Presburger]

@divyegala

raft/cpp/src/raft_runtime/neighbors/hnsw.cpp

Line 31 in b66b269

std::string filepath = "/tmp/cagra_index.bin"; \

The hardcoded file name here might not be concurrency-friendly?

[divyegala]

@Presburger thanks for pointing that out. I'll also add a random number to that file name so it is more concurrency friendly.