this will be the merge of a lifetime : SF 80 Elo+

[MikeB]

@deberger - what value should I use for NNUEThreshold2 in the updated code after today's "fallback to NNUE" push? 0? Infinite?

src/evaluate.cpp:

Code: Select all

-  constexpr Value NNUEThreshold1  =   Value(550);
+  constexpr Value NNUEThreshold1  =   VALUE_INFINITE;

There's no need to touch NNUEThreshold2 because the logical subexpression (classical && Eval::useNNUE) will always be false

Code: Select all

if (classical && Eval::useNNUE && abs(v) * 16 < NNUEThreshold2 * (16 + pos.rule50_count()))

please explain ..."There's no need to touch NNUEThreshold2 because the logical subexpression (classical && Eval::useNNUE) will always be false"

in light of the code preceding it ...

Code: Select all

Value Eval::evaluate(const Position& pos) {

  bool classical = !Eval::useNNUE
                ||  abs(eg_value(pos.psq_score())) * 16 > NNUEThreshold1 * (16 + pos.rule50_count());
  Value v = classical ? Evaluation<NO_TRACE>(pos).value()
                      : NNUE::evaluate(pos) * 5 / 4 + Tempo;

  if (classical && Eval::useNNUE && abs(v) * 16 < NNUEThreshold2 * (16 + pos.rule50_count()))
      v = NNUE::evaluate(pos) * 5 / 4 + Tempo;

  // Damp down the evaluation linearly when shuffling
  v = v * (100 - pos.rule50_count()) / 100;

  // Guarantee evalution outside of TB range
  v = Utility::clamp(v, VALUE_TB_LOSS_IN_MAX_PLY + 1, VALUE_TB_WIN_IN_MAX_PLY - 1);

  return v;
}

[Deberger]

@deberger - what value should I use for NNUEThreshold2 in the updated code after today's "fallback to NNUE" push? 0? Infinite?

There's no need to touch NNUEThreshold2 because the logical subexpression (classical && Eval::useNNUE) will always be false

Code: Select all

if (classical && Eval::useNNUE && abs(v) * 16 < NNUEThreshold2 * (16 + pos.rule50_count()))

please explain ..."There's no need to touch NNUEThreshold2 because the logical subexpression (classical && Eval::useNNUE) will always be false"

User schack was looking for a patch which uses NNUE without reverting to the classical evaluation.

With a trivial change to the source code, you can build your own executable which always uses NNUE.

Ok. What's the trivial change to the source code?

And this is the trivial change:

src/evaluate.cpp:

Code: Select all

-  constexpr Value NNUEThreshold1  =   Value(550);
+  constexpr Value NNUEThreshold1  =   VALUE_INFINITE;

If (NNUEThreshold1 == VALUE_INFINITE) then (classical == !Eval::useNNUE) and therefore (classical && Eval::useNNUE == false)

in light of the code preceding it ...

Code: Select all

Value Eval::evaluate(const Position& pos) {

  bool classical = !Eval::useNNUE
                ||  abs(eg_value(pos.psq_score())) * 16 > NNUEThreshold1 * (16 + pos.rule50_count());
  Value v = classical ? Evaluation<NO_TRACE>(pos).value()
                      : NNUE::evaluate(pos) * 5 / 4 + Tempo;

  if (classical && Eval::useNNUE && abs(v) * 16 < NNUEThreshold2 * (16 + pos.rule50_count()))
      v = NNUE::evaluate(pos) * 5 / 4 + Tempo;

  // Damp down the evaluation linearly when shuffling
  v = v * (100 - pos.rule50_count()) / 100;

  // Guarantee evalution outside of TB range
  v = Utility::clamp(v, VALUE_TB_LOSS_IN_MAX_PLY + 1, VALUE_TB_WIN_IN_MAX_PLY - 1);

  return v;
}