[iamnotempacc]

Are you trolling or what. Let's see what's written in the comment above.

> If A reduces to B, it means that an algorithm implementing B can be used (with some pre- and post-processing) to solve A.

Here we say that that we can solve a "hard problem" if we can express it in terms of the "Document Ranking" problem.

Let's rewrite that quoted sentence:

An algorithm implementing "Document Ranking" can be used (with some pre- and post-processing) to solve "Hard problem".

Let's do substitution in the first part of the sentence, "If A reduces to B", where A is "hard problem" and B is "Document Ranking":

Hard problem reduces to Document Ranking.

That means EXACTLY that we can USE Document Ranking to SOLVE the Hard Problem. Just as we wanted.

[moralestapia]

Ar-Curunir: If A reduces to B, it means that an algorithm implementing B can be used (with some pre- and post-processing) to solve A.

moralestapia: If I transform B to A and I know the solution to A, then I solved B.

Ar-Curunir: If A reduces to B, it means that B is at least as hard as A.

moralestapia: [...] B is at least as complex as A

Can you even read?