go back to swap, fix igl's usage of pred in learn

vowpalwabbit/core/include/vw/core/example.h

@@ -83,7 +83,7 @@ class polyprediction
 };
 
 std::string to_string(const v_array<float>& scalars, int decimal_precision = details::DEFAULT_FLOAT_PRECISION);
-void move_pred_to(polyprediction& src, polyprediction& dest, prediction_type_t prediction_type);
+void swap_prediction(polyprediction& a, polyprediction& b, prediction_type_t prediction_type);
 
 class example : public example_predict  // core example datatype.
 {

vowpalwabbit/core/src/example.cc

@@ -16,45 +16,45 @@
 #include <climits>
 #include <cstdint>
 
-void VW::move_pred_to(VW::polyprediction& src, VW::polyprediction& dest, VW::prediction_type_t prediction_type)
+void VW::swap_prediction(VW::polyprediction& a, VW::polyprediction& b, VW::prediction_type_t prediction_type)
 {
   switch (prediction_type)
   {
     case VW::prediction_type_t::SCALAR:
-      dest.scalar = std::move(src.scalar);
+      std::swap(b.scalar, a.scalar);
       break;
     case VW::prediction_type_t::SCALARS:
-      dest.scalars = std::move(src.scalars);
+      std::swap(b.scalars, a.scalars);
       break;
     case VW::prediction_type_t::ACTION_SCORES:
-      dest.a_s = std::move(src.a_s);
+      std::swap(b.a_s, a.a_s);
       break;
     case VW::prediction_type_t::PDF:
-      dest.pdf = std::move(src.pdf);
+      std::swap(b.pdf, a.pdf);
       break;
     case VW::prediction_type_t::ACTION_PROBS:
-      dest.a_s = std::move(src.a_s);
+      std::swap(b.a_s, a.a_s);
       break;
     case VW::prediction_type_t::MULTICLASS:
-      dest.multiclass = std::move(src.multiclass);
+      std::swap(b.multiclass, a.multiclass);
       break;
     case VW::prediction_type_t::MULTILABELS:
-      dest.multilabels = std::move(src.multilabels);
+      std::swap(b.multilabels, a.multilabels);
       break;
     case VW::prediction_type_t::PROB:
-      dest.prob = std::move(src.prob);
+      std::swap(b.prob, a.prob);
       break;
     case VW::prediction_type_t::MULTICLASS_PROBS:
-      dest.scalars = std::move(src.scalars);
+      std::swap(b.scalars, a.scalars);
       break;
     case VW::prediction_type_t::DECISION_PROBS:
-      dest.decision_scores = std::move(src.decision_scores);
+      std::swap(b.decision_scores, a.decision_scores);
       break;
     case VW::prediction_type_t::ACTION_PDF_VALUE:
-      dest.pdf_value = std::move(src.pdf_value);
+      std::swap(b.pdf_value, a.pdf_value);
       break;
     case VW::prediction_type_t::ACTIVE_MULTICLASS:
-      dest.active_multiclass = std::move(src.active_multiclass);
+      std::swap(b.active_multiclass, a.active_multiclass);
       break;
     case VW::prediction_type_t::NOPRED:
       // Noop

vowpalwabbit/core/src/global_data.cc

@@ -93,10 +93,9 @@ void workspace::learn(example& ec)
     {
       VW::LEARNER::require_singleline(l)->predict(ec);
       VW::polyprediction saved_prediction;
-      // VW::move_pred_to(ec.pred, saved_prediction, l->get_output_prediction_type());
-      // new (&ec.pred) VW::polyprediction();
+      VW::swap_prediction(ec.pred, saved_prediction, l->get_output_prediction_type());
       VW::LEARNER::require_singleline(l)->learn(ec);
-      // VW::move_pred_to(saved_prediction, ec.pred, l->get_output_prediction_type());
+      VW::swap_prediction(saved_prediction, ec.pred, l->get_output_prediction_type());
     }
   }
 }
@@ -113,10 +112,9 @@ void workspace::learn(multi_ex& ec)
     {
       VW::LEARNER::require_multiline(l)->predict(ec);
       VW::polyprediction saved_prediction;
-      // VW::move_pred_to(ec[0]->pred, saved_prediction, l->get_output_prediction_type());
-      // new (&ec[0]->pred) VW::polyprediction();
+      VW::swap_prediction(ec[0]->pred, saved_prediction, l->get_output_prediction_type());
       VW::LEARNER::require_multiline(l)->learn(ec);
-      // VW::move_pred_to(saved_prediction, ec[0]->pred, l->get_output_prediction_type());
+      VW::swap_prediction(saved_prediction, ec[0]->pred, l->get_output_prediction_type());
     }
   }
 }

vowpalwabbit/core/src/reductions/interaction_ground.cc

@@ -122,8 +122,42 @@ void add_obs_features_to_ik_ex(VW::example& ik_ex, const VW::example& obs_ex)
   }
 }
 
+void predict(VW::reductions::igl::igl_data& igl, learner& base, VW::multi_ex& ec_seq)
+{
+  VW::example* observation_ex = nullptr;
+
+  if (ec_seq.size() > 0 && ec_seq.back()->l.cb_with_observations.is_observation)
+  {
+    observation_ex = ec_seq.back();
+    ec_seq.pop_back();
+  }
+
+  std::swap(*igl.pi_ftrl.get(), *igl.ik_ftrl);
+
+  for (auto& ex : ec_seq)
+  {
+    ex->l.cb = ex->l.cb_with_observations.event;
+    ex->l.cb_with_observations.event.reset_to_default();
+  }
+
+  base.predict(ec_seq, 1);
+  std::swap(*igl.pi_ftrl.get(), *igl.ik_ftrl);
+
+  for (auto& ex : ec_seq)
+  {
+    ex->l.cb_with_observations.event = ex->l.cb;
+    ex->l.cb.reset_to_default();
+  }
+
+  if (observation_ex != nullptr) { ec_seq.push_back(observation_ex); }
+}
+
 void learn(VW::reductions::igl::igl_data& igl, learner& base, VW::multi_ex& ec_seq)
 {
+  predict(igl, base, ec_seq);
+
+  auto stashed_prediction = ec_seq[0]->pred.a_s;
+
   float p_unlabeled_prior = 0.5f;
 
   std::swap(igl.ik_ftrl->all->loss_config.loss, igl.ik_all->loss_config.loss);
@@ -212,36 +246,7 @@ void learn(VW::reductions::igl::igl_data& igl, learner& base, VW::multi_ex& ec_s
   }
 
   ec_seq.push_back(observation_ex);
-}
-
-void predict(VW::reductions::igl::igl_data& igl, learner& base, VW::multi_ex& ec_seq)
-{
-  VW::example* observation_ex = nullptr;
-
-  if (ec_seq.size() > 0 && ec_seq.back()->l.cb_with_observations.is_observation)
-  {
-    observation_ex = ec_seq.back();
-    ec_seq.pop_back();
-  }
-
-  std::swap(*igl.pi_ftrl.get(), *igl.ik_ftrl);
-
-  for (auto& ex : ec_seq)
-  {
-    ex->l.cb = ex->l.cb_with_observations.event;
-    ex->l.cb_with_observations.event.reset_to_default();
-  }
-
-  base.predict(ec_seq, 1);
-  std::swap(*igl.pi_ftrl.get(), *igl.ik_ftrl);
-
-  for (auto& ex : ec_seq)
-  {
-    ex->l.cb_with_observations.event = ex->l.cb;
-    ex->l.cb.reset_to_default();
-  }
-
-  if (observation_ex != nullptr) { ec_seq.push_back(observation_ex); }
+  ec_seq[0]->pred.a_s = std::move(stashed_prediction);
 }
 
 void save_load_igl(VW::reductions::igl::igl_data& igl, VW::io_buf& io, bool read, bool text)
@@ -415,6 +420,7 @@ std::shared_ptr<VW::LEARNER::learner> VW::reductions::interaction_ground_setup(V
   auto l = make_reduction_learner(
       std::move(ld), pi_learner, learn, predict, stack_builder.get_setupfn_name(interaction_ground_setup))
                .set_feature_width(feature_width)
+               .set_learn_returns_prediction(true)
                .set_input_label_type(label_type_t::CB_WITH_OBSERVATIONS)
                .set_output_label_type(label_type_t::CB)
                .set_input_prediction_type(pred_type)