bel_hash.cpp

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/*---------------------------------------------------------------------+
 * File: bel_hash.cpp
 * Project: part of belofte - A Promising Chess Program
 * Author: yves
 * SPDX-License-Identifier: GPL-2.0-only
+----------------------------------------------------------------------*/
 
#include "belofte.h"
 
hashkey_t hashmultiplexer[tPiece::P_SIZE][64];
 
void bel_hash::delayed_ctor()
{
  if (!m_isFullInit) {
    // piece keys, special moves are in piece empty location
    for (int i = 0; i < tPiece::P_SIZE; ++i) {
      for (case_t iCase = 0; iCase < 64; ++iCase) {
        hashmultiplexer[i][iCase] = getRandom();
      }
    }
 
    m_isFullInit = true;
  }
}
 
/** return hashkey, as rand is giving by definition
 * result in between 0 and 32768, do not take the risk of zero bits
 * and shift possibly getting bits falling off
 * specification is only giving 15 significant bits, as we do not need
 * upper bits, take this into account
 */
hashkey_t bel_hash::getRandom(void) {
  hashkey_t r = (rand() & 0x8FFF); // ensure same result independent of platform
  r = (r << 15) + (rand() & 0x8FFF);
  r = (r << 15) + (rand() & 0x8FFF);
  r = (r << 15) + (rand() & 0x8FFF);
  r = r & 0x00FFFFFFFFFFFFFFLL; // strip off higher 8 bits
  return r;
}
 
// eof