search_multiclasstask.cc

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/*
  CoPyright (c) by respective owners including Yahoo!, Microsoft, and
  individual contributors. All rights reserved.  Released under a BSD (revised)
  license as described in the file LICENSE.
*/
#include "search_multiclasstask.h"

namespace MulticlassTask
{
Search::search_task task = {"multiclasstask", run, initialize, finish, nullptr, nullptr};
}

namespace MulticlassTask
{
struct task_data
{
  size_t max_label;
  size_t num_level;
  v_array<uint32_t> y_allowed;
};

void initialize(Search::search& sch, size_t& num_actions, VW::config::options_i& /*vm*/)
{
  task_data* my_task_data = new task_data();
  sch.set_options(0);
  sch.set_num_learners(num_actions);
  my_task_data->max_label = num_actions;
  my_task_data->num_level = (size_t)ceil(log(num_actions) / log(2));
  my_task_data->y_allowed.push_back(1);
  my_task_data->y_allowed.push_back(2);
  sch.set_task_data(my_task_data);
}

void finish(Search::search& sch)
{
  task_data* my_task_data = sch.get_task_data<task_data>();
  my_task_data->y_allowed.delete_v();
  delete my_task_data;
}

void run(Search::search& sch, multi_ex& ec)
{
  task_data* my_task_data = sch.get_task_data<task_data>();
  size_t gold_label = ec[0]->l.multi.label;
  size_t label = 0;
  size_t learner_id = 0;

  for (size_t i = 0; i < my_task_data->num_level; i++)
  {
    size_t mask = UINT64_ONE << (my_task_data->num_level - i - 1);
    size_t y_allowed_size = (label + mask + 1 <= my_task_data->max_label) ? 2 : 1;
    action oracle = (((gold_label - 1) & mask) > 0) + 1;
    size_t prediction = sch.predict(*ec[0], 0, &oracle, 1, nullptr, nullptr, my_task_data->y_allowed.begin(),
        y_allowed_size, nullptr, learner_id);  // TODO: do we really need y_allowed?
    learner_id = (learner_id << 1) + prediction;
    if (prediction == 2)
      label += mask;
  }
  label += 1;
  sch.loss(!(label == gold_label));
  if (sch.output().good())
    sch.output() << label << ' ';
}
}  // namespace MulticlassTask