Fastest way to find position of elements in a list

Question

I need to identify the position inside list of the elements in target. Straightforward solution:

Timing[target // Map[Position[list, #] &] ;

15s

I needed a faster algorithm for my real case. Here is my try but any completely different solution is also very welcome. I assigned a score to each element, compared scores first, then look for the specific element within the candidates.

Timing[target // Map[identifyTerms];]

2.5s

But this is still not fast enough (in the real case)

Here my dummy example I made for this question:

(*list and target*)

list = {a, b, c, d, e, f, g, h} // Permutations[#, {2, 7}] & // 
    RandomSample // Map[Dot @@ # &];

target = {a, b, c, d, e, f} // Permutations[#, {2, 5}] & // 
   Map[Dot @@ # &];

(*simple target: target={a.b.c}*)
(*simple list: list={a, b.f, a.b.c}*)


(*functions*)

getScore[expr_] := 
 expr /. {a -> 1, b -> 2, c -> 3, d -> 4, e -> 5, f -> 6, g -> 7, 
    h -> 8} /. Dot -> Times

listScores = list // getScore;
identifyTerms[expr_] := Module[{cand, p},
   cand = Position[listScores, getScore[expr]] // Flatten;
   p = Position[list[[cand]], expr] // Flatten;
   cand[[p]]];

Answer 1

As discussed in the comments, the best way to solve this problem is to first use PositionIndex to create a hash table up front so WL doesn't have to keep doing the same thing over and over:

posInd = PositionIndex[list];
Lookup[posInd, target]

or

Lookup[posInd, #]& /@ target