original and optimized versions were run and benchmarked on the
following program:

```ocaml
let () =
  let open Codepi.Orthomam in
  let loggers = [ Bistro_utils.Console_logger.create () ] in
  let db = Codepitk.Orthomam_db.make "_runs/omm" in
  let q =
    search_alignments ~pat:"*GPR87" db
    |> List.hd
    |> query ~convergent_species:(Bistro.Workflow.data species_with_echolocation)
  in
  inhouse_tdg09 q
  |> Bistro.Workflow.path
  |> Bistro_engine.Scheduler.simple_eval_exn ~loggers
  |> print_endline
```

execution time got from 24min to 18s, apparently with very little
changes on pvalue results (after the 6th decimal)