Create README.md

#include <iomanip>
#include <iostream>
#include <sstream>
#include <string>

#include "evaluate.h"
#include "notation.h"
#include "position.h"
#include "search.h"
#include "thread.h"
#include "tt.h"
#include "ucioption.h"

using namespace std;

extern void benchmark(const Position& pos, istream& is);

namespace {

  // FEN string of the initial position, normal chess
  const char* StartFEN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";

  // Keep a track of the position keys along the setup moves (from the start position
  // to the position just before the search starts). This is needed by the repetition
  // draw detection code.
  Search::StateStackPtr SetupStates;
  Position currentPos;

  // position() is called when engine receives the "position" UCI command.
  // The function sets up the position described in the given FEN string ("fen")
  // or the starting position ("startpos") and then makes the moves given in the
  // following move list ("moves").

  void position(Position& pos, istringstream& is) {

    Move m;
    string token, fen;

    is >> token;

    if (token == "startpos")
    {
        fen = StartFEN;
        is >> token; // Consume "moves" token if any
    }
    else if (token == "fen")
        while (is >> token && token != "moves")
            fen += token + " ";
    else
        return;

    pos.set(fen, Options["UCI_Chess960"], Threads.main());
    SetupStates = Search::StateStackPtr(new std::stack<StateInfo>());

    // Parse move list (if any)
    while (is >> token && (m = move_from_uci(pos, token)) != MOVE_NONE)
    {
        SetupStates->push(StateInfo());
        pos.do_move(m, SetupStates->top());
    }
  }


  // setoption() is called when engine receives the "setoption" UCI command. The
  // function updates the UCI option ("name") to the given value ("value").

  void setoption(istringstream& is) {

    string token, name, value;

    is >> token; // Consume "name" token

    // Read option name (can contain spaces)
    while (is >> token && token != "value")
        name += string(" ", !name.empty()) + token;

    // Read option value (can contain spaces)
    while (is >> token)
        value += string(" ", !value.empty()) + token;

    if (Options.count(name))
        Options[name] = value;
    else
        sync_cout << "No such option: " << name << sync_endl;
  }


  // go() is called when engine receives the "go" UCI command. The function sets
  // the thinking time and other parameters from the input string, and starts
  // the search.

  void go(const Position& pos, istringstream& is) {

    Search::LimitsType limits;
    string token;

    while (is >> token)
    {
        if (token == "searchmoves")
            while (is >> token)
                limits.searchmoves.push_back(move_from_uci(pos, token));

        else if (token == "wtime")     is >> limits.time[WHITE];
        else if (token == "btime")     is >> limits.time[BLACK];
        else if (token == "winc")      is >> limits.inc[WHITE];
        else if (token == "binc")      is >> limits.inc[BLACK];
        else if (token == "movestogo") is >> limits.movestogo;
        else if (token == "depth")     is >> limits.depth;
        else if (token == "nodes")     is >> limits.nodes;
        else if (token == "movetime")  is >> limits.movetime;
        else if (token == "mate")      is >> limits.mate;
        else if (token == "infinite")  limits.infinite = true;
        else if (token == "ponder")    limits.ponder = true;
    }

    Threads.start_thinking(pos, limits, SetupStates);
  }

} // namespace


/// Wait for a command from the user, parse this text string as an UCI command,
/// and call the appropriate functions. Also intercepts EOF from stdin to ensure
/// that we exit gracefully if the GUI dies unexpectedly. In addition to the UCI
/// commands, the function also supports a few debug commands.

void UCI::commandInit() {
	currentPos = Position(StartFEN, false, Threads.main()); // The root position
}

void UCI::command(const string& cmd) {
  istringstream is(cmd);

  string token;
  is >> skipws >> token;

  if (token == "quit" || token == "stop" || token == "ponderhit")
  {
      // The GUI sends 'ponderhit' to tell us to ponder on the same move the
      // opponent has played. In case Signals.stopOnPonderhit is set we are
      // waiting for 'ponderhit' to stop the search (for instance because we
      // already ran out of time), otherwise we should continue searching but
      // switch from pondering to normal search.
      if (token != "ponderhit" || Search::Signals.stopOnPonderhit)
      {
          Search::Signals.stop = true;
          Threads.main()->notify_one(); // Could be sleeping
      }
      else
          Search::Limits.ponder = false;
  }
  else if (token == "perft" || token == "divide")
  {
      int depth;
      stringstream ss;

      is >> depth;
      ss << Options["Hash"]    << " "
         << Options["Threads"] << " " << depth << " current " << token;

      benchmark(currentPos, ss);
  }
  else if (token == "key")
      sync_cout << hex << uppercase << setfill('0')
                << "position key: "   << setw(16) << currentPos.key()
                << "\nmaterial key: " << setw(16) << currentPos.material_key()
                << "\npawn key:     " << setw(16) << currentPos.pawn_key()
                << dec << nouppercase << setfill(' ') << sync_endl;

  else if (token == "uci")
      sync_cout << "id name " << engine_info(true)
                << "\n"       << Options
                << "\nuciok"  << sync_endl;

  else if (token == "eval")
  {
      Search::RootColor = currentPos.side_to_move(); // Ensure it is set
      sync_cout << Eval::trace(currentPos) << sync_endl;
  }
  else if (token == "ucinewgame") TT.clear();
  else if (token == "go")         go(currentPos, is);
  else if (token == "position")   position(currentPos, is);
  else if (token == "setoption")  setoption(is);
  else if (token == "flip")       currentPos.flip();
  else if (token == "bench")      benchmark(currentPos, is);
  else if (token == "d")          sync_cout << currentPos.pretty() << sync_endl;
  else if (token == "isready")    sync_cout << "readyok" << sync_endl;
  else
      sync_cout << "Unknown command: " << cmd << sync_endl;
}