/*
  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
  Copyright (C) 2008-2009 Marco Costalba

  Stockfish is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Stockfish is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/


/*
  The code in this file is based on the opening book code in PolyGlot
  by Fabien Letouzey.  PolyGlot is available under the GNU General
  Public License, and can be downloaded from http://wbec-ridderkerk.nl
*/


////
//// Includes
////

#include <cassert>

#include "book.h"
#include "mersenne.h"
#include "movegen.h"

using namespace std;

////
//// Global variables
////

Book OpeningBook;


////
//// Local definitions
////

namespace {

  /// Book entry size in bytes
  const int EntrySize = 16;


  /// Random numbers from PolyGlot, used to compute book hash keys

  const uint64_t Random64[781] = {
    0x9D39247E33776D41ULL, 0x2AF7398005AAA5C7ULL, 0x44DB015024623547ULL,
    0x9C15F73E62A76AE2ULL, 0x75834465489C0C89ULL, 0x3290AC3A203001BFULL,
    0x0FBBAD1F61042279ULL, 0xE83A908FF2FB60CAULL, 0x0D7E765D58755C10ULL,
    0x1A083822CEAFE02DULL, 0x9605D5F0E25EC3B0ULL, 0xD021FF5CD13A2ED5ULL,
    0x40BDF15D4A672E32ULL, 0x011355146FD56395ULL, 0x5DB4832046F3D9E5ULL,
    0x239F8B2D7FF719CCULL, 0x05D1A1AE85B49AA1ULL, 0x679F848F6E8FC971ULL,
    0x7449BBFF801FED0BULL, 0x7D11CDB1C3B7ADF0ULL, 0x82C7709E781EB7CCULL,
    0xF3218F1C9510786CULL, 0x331478F3AF51BBE6ULL, 0x4BB38DE5E7219443ULL,
    0xAA649C6EBCFD50FCULL, 0x8DBD98A352AFD40BULL, 0x87D2074B81D79217ULL,
    0x19F3C751D3E92AE1ULL, 0xB4AB30F062B19ABFULL, 0x7B0500AC42047AC4ULL,
    0xC9452CA81A09D85DULL, 0x24AA6C514DA27500ULL, 0x4C9F34427501B447ULL,
    0x14A68FD73C910841ULL, 0xA71B9B83461CBD93ULL, 0x03488B95B0F1850FULL,
    0x637B2B34FF93C040ULL, 0x09D1BC9A3DD90A94ULL, 0x3575668334A1DD3BULL,
    0x735E2B97A4C45A23ULL, 0x18727070F1BD400BULL, 0x1FCBACD259BF02E7ULL,
    0xD310A7C2CE9B6555ULL, 0xBF983FE0FE5D8244ULL, 0x9F74D14F7454A824ULL,
    0x51EBDC4AB9BA3035ULL, 0x5C82C505DB9AB0FAULL, 0xFCF7FE8A3430B241ULL,
    0x3253A729B9BA3DDEULL, 0x8C74C368081B3075ULL, 0xB9BC6C87167C33E7ULL,
    0x7EF48F2B83024E20ULL, 0x11D505D4C351BD7FULL, 0x6568FCA92C76A243ULL,
    0x4DE0B0F40F32A7B8ULL, 0x96D693460CC37E5DULL, 0x42E240CB63689F2FULL,
    0x6D2BDCDAE2919661ULL, 0x42880B0236E4D951ULL, 0x5F0F4A5898171BB6ULL,
    0x39F890F579F92F88ULL, 0x93C5B5F47356388BULL, 0x63DC359D8D231B78ULL,
    0xEC16CA8AEA98AD76ULL, 0x5355F900C2A82DC7ULL, 0x07FB9F855A997142ULL,
    0x5093417AA8A7ED5EULL, 0x7BCBC38DA25A7F3CULL, 0x19FC8A768CF4B6D4ULL,
    0x637A7780DECFC0D9ULL, 0x8249A47AEE0E41F7ULL, 0x79AD695501E7D1E8ULL,
    0x14ACBAF4777D5776ULL, 0xF145B6BECCDEA195ULL, 0xDABF2AC8201752FCULL,
    0x24C3C94DF9C8D3F6ULL, 0xBB6E2924F03912EAULL, 0x0CE26C0B95C980D9ULL,
    0xA49CD132BFBF7CC4ULL, 0xE99D662AF4243939ULL, 0x27E6AD7891165C3FULL,
    0x8535F040B9744FF1ULL, 0x54B3F4FA5F40D873ULL, 0x72B12C32127FED2BULL,
    0xEE954D3C7B411F47ULL, 0x9A85AC909A24EAA1ULL, 0x70AC4CD9F04F21F5ULL,
    0xF9B89D3E99A075C2ULL, 0x87B3E2B2B5C907B1ULL, 0xA366E5B8C54F48B8ULL,
    0xAE4A9346CC3F7CF2ULL, 0x1920C04D47267BBDULL, 0x87BF02C6B49E2AE9ULL,
    0x092237AC237F3859ULL, 0xFF07F64EF8ED14D0ULL, 0x8DE8DCA9F03CC54EULL,
    0x9C1633264DB49C89ULL, 0xB3F22C3D0B0B38EDULL, 0x390E5FB44D01144BULL,
    0x5BFEA5B4712768E9ULL, 0x1E1032911FA78984ULL, 0x9A74ACB964E78CB3ULL,
    0x4F80F7A035DAFB04ULL, 0x6304D09A0B3738C4ULL, 0x2171E64683023A08ULL,
    0x5B9B63EB9CEFF80CULL, 0x506AACF489889342ULL, 0x1881AFC9A3A701D6ULL,
    0x6503080440750644ULL, 0xDFD395339CDBF4A7ULL, 0xEF927DBCF00C20F2ULL,
    0x7B32F7D1E03680ECULL, 0xB9FD7620E7316243ULL, 0x05A7E8A57DB91B77ULL,
    0xB5889C6E15630A75ULL, 0x4A750A09CE9573F7ULL, 0xCF464CEC899A2F8AULL,
    0xF538639CE705B824ULL, 0x3C79A0FF5580EF7FULL, 0xEDE6C87F8477609DULL,
    0x799E81F05BC93F31ULL, 0x86536B8CF3428A8CULL, 0x97D7374C60087B73ULL,
    0xA246637CFF328532ULL, 0x043FCAE60CC0EBA0ULL, 0x920E449535DD359EULL,
    0x70EB093B15B290CCULL, 0x73A1921916591CBDULL, 0x56436C9FE1A1AA8DULL,
    0xEFAC4B70633B8F81ULL, 0xBB215798D45DF7AFULL, 0x45F20042F24F1768ULL,
    0x930F80F4E8EB7462ULL, 0xFF6712FFCFD75EA1ULL, 0xAE623FD67468AA70ULL,
    0xDD2C5BC84BC8D8FCULL, 0x7EED120D54CF2DD9ULL, 0x22FE545401165F1CULL,
    0xC91800E98FB99929ULL, 0x808BD68E6AC10365ULL, 0xDEC468145B7605F6ULL,
    0x1BEDE3A3AEF53302ULL, 0x43539603D6C55602ULL, 0xAA969B5C691CCB7AULL,
    0xA87832D392EFEE56ULL, 0x65942C7B3C7E11AEULL, 0xDED2D633CAD004F6ULL,
    0x21F08570F420E565ULL, 0xB415938D7DA94E3CULL, 0x91B859E59ECB6350ULL,
    0x10CFF333E0ED804AULL, 0x28AED140BE0BB7DDULL, 0xC5CC1D89724FA456ULL,
    0x5648F680F11A2741ULL, 0x2D255069F0B7DAB3ULL, 0x9BC5A38EF729ABD4ULL,
    0xEF2F054308F6A2BCULL, 0xAF2042F5CC5C2858ULL, 0x480412BAB7F5BE2AULL,
    0xAEF3AF4A563DFE43ULL, 0x19AFE59AE451497FULL, 0x52593803DFF1E840ULL,
    0xF4F076E65F2CE6F0ULL, 0x11379625747D5AF3ULL, 0xBCE5D2248682C115ULL,
    0x9DA4243DE836994FULL, 0x066F70B33FE09017ULL, 0x4DC4DE189B671A1CULL,
    0x51039AB7712457C3ULL, 0xC07A3F80C31FB4B4ULL, 0xB46EE9C5E64A6E7CULL,
    0xB3819A42ABE61C87ULL, 0x21A007933A522A20ULL, 0x2DF16F761598AA4FULL,
    0x763C4A1371B368FDULL, 0xF793C46702E086A0ULL, 0xD7288E012AEB8D31ULL,
    0xDE336A2A4BC1C44BULL, 0x0BF692B38D079F23ULL, 0x2C604A7A177326B3ULL,
    0x4850E73E03EB6064ULL, 0xCFC447F1E53C8E1BULL, 0xB05CA3F564268D99ULL,
    0x9AE182C8BC9474E8ULL, 0xA4FC4BD4FC5558CAULL, 0xE755178D58FC4E76ULL,
    0x69B97DB1A4C03DFEULL, 0xF9B5B7C4ACC67C96ULL, 0xFC6A82D64B8655FBULL,
    0x9C684CB6C4D24417ULL, 0x8EC97D2917456ED0ULL, 0x6703DF9D2924E97EULL,
    0xC547F57E42A7444EULL, 0x78E37644E7CAD29EULL, 0xFE9A44E9362F05FAULL,
    0x08BD35CC38336615ULL, 0x9315E5EB3A129ACEULL, 0x94061B871E04DF75ULL,
    0xDF1D9F9D784BA010ULL, 0x3BBA57B68871B59DULL, 0xD2B7ADEEDED1F73FULL,
    0xF7A255D83BC373F8ULL, 0xD7F4F2448C0CEB81ULL, 0xD95BE88CD210FFA7ULL,
    0x336F52F8FF4728E7ULL, 0xA74049DAC312AC71ULL, 0xA2F61BB6E437FDB5ULL,
    0x4F2A5CB07F6A35B3ULL, 0x87D380BDA5BF7859ULL, 0x16B9F7E06C453A21ULL,
    0x7BA2484C8A0FD54EULL, 0xF3A678CAD9A2E38CULL, 0x39B0BF7DDE437BA2ULL,
    0xFCAF55C1BF8A4424ULL, 0x18FCF680573FA594ULL, 0x4C0563B89F495AC3ULL,
    0x40E087931A00930DULL, 0x8CFFA9412EB642C1ULL, 0x68CA39053261169FULL,
    0x7A1EE967D27579E2ULL, 0x9D1D60E5076F5B6FULL, 0x3810E399B6F65BA2ULL,
    0x32095B6D4AB5F9B1ULL, 0x35CAB62109DD038AULL, 0xA90B24499FCFAFB1ULL,
    0x77A225A07CC2C6BDULL, 0x513E5E634C70E331ULL, 0x4361C0CA3F692F12ULL,
    0xD941ACA44B20A45BULL, 0x528F7C8602C5807BULL, 0x52AB92BEB9613989ULL,
    0x9D1DFA2EFC557F73ULL, 0x722FF175F572C348ULL, 0x1D1260A51107FE97ULL,
    0x7A249A57EC0C9BA2ULL, 0x04208FE9E8F7F2D6ULL, 0x5A110C6058B920A0ULL,
    0x0CD9A497658A5698ULL, 0x56FD23C8F9715A4CULL, 0x284C847B9D887AAEULL,
    0x04FEABFBBDB619CBULL, 0x742E1E651C60BA83ULL, 0x9A9632E65904AD3CULL,
    0x881B82A13B51B9E2ULL, 0x506E6744CD974924ULL, 0xB0183DB56FFC6A79ULL,
    0x0ED9B915C66ED37EULL, 0x5E11E86D5873D484ULL, 0xF678647E3519AC6EULL,
    0x1B85D488D0F20CC5ULL, 0xDAB9FE6525D89021ULL, 0x0D151D86ADB73615ULL,
    0xA865A54EDCC0F019ULL, 0x93C42566AEF98FFBULL, 0x99E7AFEABE000731ULL,
    0x48CBFF086DDF285AULL, 0x7F9B6AF1EBF78BAFULL, 0x58627E1A149BBA21ULL,
    0x2CD16E2ABD791E33ULL, 0xD363EFF5F0977996ULL, 0x0CE2A38C344A6EEDULL,
    0x1A804AADB9CFA741ULL, 0x907F30421D78C5DEULL, 0x501F65EDB3034D07ULL,
    0x37624AE5A48FA6E9ULL, 0x957BAF61700CFF4EULL, 0x3A6C27934E31188AULL,
    0xD49503536ABCA345ULL, 0x088E049589C432E0ULL, 0xF943AEE7FEBF21B8ULL,
    0x6C3B8E3E336139D3ULL, 0x364F6FFA464EE52EULL, 0xD60F6DCEDC314222ULL,
    0x56963B0DCA418FC0ULL, 0x16F50EDF91E513AFULL, 0xEF1955914B609F93ULL,
    0x565601C0364E3228ULL, 0xECB53939887E8175ULL, 0xBAC7A9A18531294BULL,
    0xB344C470397BBA52ULL, 0x65D34954DAF3CEBDULL, 0xB4B81B3FA97511E2ULL,
    0xB422061193D6F6A7ULL, 0x071582401C38434DULL, 0x7A13F18BBEDC4FF5ULL,
    0xBC4097B116C524D2ULL, 0x59B97885E2F2EA28ULL, 0x99170A5DC3115544ULL,
    0x6F423357E7C6A9F9ULL, 0x325928EE6E6F8794ULL, 0xD0E4366228B03343ULL,
    0x565C31F7DE89EA27ULL, 0x30F5611484119414ULL, 0xD873DB391292ED4FULL,
    0x7BD94E1D8E17DEBCULL, 0xC7D9F16864A76E94ULL, 0x947AE053EE56E63CULL,
    0xC8C93882F9475F5FULL, 0x3A9BF55BA91F81CAULL, 0xD9A11FBB3D9808E4ULL,
    0x0FD22063EDC29FCAULL, 0xB3F256D8ACA0B0B9ULL, 0xB03031A8B4516E84ULL,
    0x35DD37D5871448AFULL, 0xE9F6082B05542E4EULL, 0xEBFAFA33D7254B59ULL,
    0x9255ABB50D532280ULL, 0xB9AB4CE57F2D34F3ULL, 0x693501D628297551ULL,
    0xC62C58F97DD949BFULL, 0xCD454F8F19C5126AULL, 0xBBE83F4ECC2BDECBULL,
    0xDC842B7E2819E230ULL, 0xBA89142E007503B8ULL, 0xA3BC941D0A5061CBULL,
    0xE9F6760E32CD8021ULL, 0x09C7E552BC76492FULL, 0x852F54934DA55CC9ULL,
    0x8107FCCF064FCF56ULL, 0x098954D51FFF6580ULL, 0x23B70EDB1955C4BFULL,
    0xC330DE426430F69DULL, 0x4715ED43E8A45C0AULL, 0xA8D7E4DAB780A08DULL,
    0x0572B974F03CE0BBULL, 0xB57D2E985E1419C7ULL, 0xE8D9ECBE2CF3D73FULL,
    0x2FE4B17170E59750ULL, 0x11317BA87905E790ULL, 0x7FBF21EC8A1F45ECULL,
    0x1725CABFCB045B00ULL, 0x964E915CD5E2B207ULL, 0x3E2B8BCBF016D66DULL,
    0xBE7444E39328A0ACULL, 0xF85B2B4FBCDE44B7ULL, 0x49353FEA39BA63B1ULL,
    0x1DD01AAFCD53486AULL, 0x1FCA8A92FD719F85ULL, 0xFC7C95D827357AFAULL,
    0x18A6A990C8B35EBDULL, 0xCCCB7005C6B9C28DULL, 0x3BDBB92C43B17F26ULL,
    0xAA70B5B4F89695A2ULL, 0xE94C39A54A98307FULL, 0xB7A0B174CFF6F36EULL,
    0xD4DBA84729AF48ADULL, 0x2E18BC1AD9704A68ULL, 0x2DE0966DAF2F8B1CULL,
    0xB9C11D5B1E43A07EULL, 0x64972D68DEE33360ULL, 0x94628D38D0C20584ULL,
    0xDBC0D2B6AB90A559ULL, 0xD2733C4335C6A72FULL, 0x7E75D99D94A70F4DULL,
    0x6CED1983376FA72BULL, 0x97FCAACBF030BC24ULL, 0x7B77497B32503B12ULL,
    0x8547EDDFB81CCB94ULL, 0x79999CDFF70902CBULL, 0xCFFE1939438E9B24ULL,
    0x829626E3892D95D7ULL, 0x92FAE24291F2B3F1ULL, 0x63E22C147B9C3403ULL,
    0xC678B6D860284A1CULL, 0x5873888850659AE7ULL, 0x0981DCD296A8736DULL,
    0x9F65789A6509A440ULL, 0x9FF38FED72E9052FULL, 0xE479EE5B9930578CULL,
    0xE7F28ECD2D49EECDULL, 0x56C074A581EA17FEULL, 0x5544F7D774B14AEFULL,
    0x7B3F0195FC6F290FULL, 0x12153635B2C0CF57ULL, 0x7F5126DBBA5E0CA7ULL,
    0x7A76956C3EAFB413ULL, 0x3D5774A11D31AB39ULL, 0x8A1B083821F40CB4ULL,
    0x7B4A38E32537DF62ULL, 0x950113646D1D6E03ULL, 0x4DA8979A0041E8A9ULL,
    0x3BC36E078F7515D7ULL, 0x5D0A12F27AD310D1ULL, 0x7F9D1A2E1EBE1327ULL,
    0xDA3A361B1C5157B1ULL, 0xDCDD7D20903D0C25ULL, 0x36833336D068F707ULL,
    0xCE68341F79893389ULL, 0xAB9090168DD05F34ULL, 0x43954B3252DC25E5ULL,
    0xB438C2B67F98E5E9ULL, 0x10DCD78E3851A492ULL, 0xDBC27AB5447822BFULL,
    0x9B3CDB65F82CA382ULL, 0xB67B7896167B4C84ULL, 0xBFCED1B0048EAC50ULL,
    0xA9119B60369FFEBDULL, 0x1FFF7AC80904BF45ULL, 0xAC12FB171817EEE7ULL,
    0xAF08DA9177DDA93DULL, 0x1B0CAB936E65C744ULL, 0xB559EB1D04E5E932ULL,
    0xC37B45B3F8D6F2BAULL, 0xC3A9DC228CAAC9E9ULL, 0xF3B8B6675A6507FFULL,
    0x9FC477DE4ED681DAULL, 0x67378D8ECCEF96CBULL, 0x6DD856D94D259236ULL,
    0xA319CE15B0B4DB31ULL, 0x073973751F12DD5EULL, 0x8A8E849EB32781A5ULL,
    0xE1925C71285279F5ULL, 0x74C04BF1790C0EFEULL, 0x4DDA48153C94938AULL,
    0x9D266D6A1CC0542CULL, 0x7440FB816508C4FEULL, 0x13328503DF48229FULL,
    0xD6BF7BAEE43CAC40ULL, 0x4838D65F6EF6748FULL, 0x1E152328F3318DEAULL,
    0x8F8419A348F296BFULL, 0x72C8834A5957B511ULL, 0xD7A023A73260B45CULL,
    0x94EBC8ABCFB56DAEULL, 0x9FC10D0F989993E0ULL, 0xDE68A2355B93CAE6ULL,
    0xA44CFE79AE538BBEULL, 0x9D1D84FCCE371425ULL, 0x51D2B1AB2DDFB636ULL,
    0x2FD7E4B9E72CD38CULL, 0x65CA5B96B7552210ULL, 0xDD69A0D8AB3B546DULL,
    0x604D51B25FBF70E2ULL, 0x73AA8A564FB7AC9EULL, 0x1A8C1E992B941148ULL,
    0xAAC40A2703D9BEA0ULL, 0x764DBEAE7FA4F3A6ULL, 0x1E99B96E70A9BE8BULL,
    0x2C5E9DEB57EF4743ULL, 0x3A938FEE32D29981ULL, 0x26E6DB8FFDF5ADFEULL,
    0x469356C504EC9F9DULL, 0xC8763C5B08D1908CULL, 0x3F6C6AF859D80055ULL,
    0x7F7CC39420A3A545ULL, 0x9BFB227EBDF4C5CEULL, 0x89039D79D6FC5C5CULL,
    0x8FE88B57305E2AB6ULL, 0xA09E8C8C35AB96DEULL, 0xFA7E393983325753ULL,
    0xD6B6D0ECC617C699ULL, 0xDFEA21EA9E7557E3ULL, 0xB67C1FA481680AF8ULL,
    0xCA1E3785A9E724E5ULL, 0x1CFC8BED0D681639ULL, 0xD18D8549D140CAEAULL,
    0x4ED0FE7E9DC91335ULL, 0xE4DBF0634473F5D2ULL, 0x1761F93A44D5AEFEULL,
    0x53898E4C3910DA55ULL, 0x734DE8181F6EC39AULL, 0x2680B122BAA28D97ULL,
    0x298AF231C85BAFABULL, 0x7983EED3740847D5ULL, 0x66C1A2A1A60CD889ULL,
    0x9E17E49642A3E4C1ULL, 0xEDB454E7BADC0805ULL, 0x50B704CAB602C329ULL,
    0x4CC317FB9CDDD023ULL, 0x66B4835D9EAFEA22ULL, 0x219B97E26FFC81BDULL,
    0x261E4E4C0A333A9DULL, 0x1FE2CCA76517DB90ULL, 0xD7504DFA8816EDBBULL,
    0xB9571FA04DC089C8ULL, 0x1DDC0325259B27DEULL, 0xCF3F4688801EB9AAULL,
    0xF4F5D05C10CAB243ULL, 0x38B6525C21A42B0EULL, 0x36F60E2BA4FA6800ULL,
    0xEB3593803173E0CEULL, 0x9C4CD6257C5A3603ULL, 0xAF0C317D32ADAA8AULL,
    0x258E5A80C7204C4BULL, 0x8B889D624D44885DULL, 0xF4D14597E660F855ULL,
    0xD4347F66EC8941C3ULL, 0xE699ED85B0DFB40DULL, 0x2472F6207C2D0484ULL,
    0xC2A1E7B5B459AEB5ULL, 0xAB4F6451CC1D45ECULL, 0x63767572AE3D6174ULL,
    0xA59E0BD101731A28ULL, 0x116D0016CB948F09ULL, 0x2CF9C8CA052F6E9FULL,
    0x0B090A7560A968E3ULL, 0xABEEDDB2DDE06FF1ULL, 0x58EFC10B06A2068DULL,
    0xC6E57A78FBD986E0ULL, 0x2EAB8CA63CE802D7ULL, 0x14A195640116F336ULL,
    0x7C0828DD624EC390ULL, 0xD74BBE77E6116AC7ULL, 0x804456AF10F5FB53ULL,
    0xEBE9EA2ADF4321C7ULL, 0x03219A39EE587A30ULL, 0x49787FEF17AF9924ULL,
    0xA1E9300CD8520548ULL, 0x5B45E522E4B1B4EFULL, 0xB49C3B3995091A36ULL,
    0xD4490AD526F14431ULL, 0x12A8F216AF9418C2ULL, 0x001F837CC7350524ULL,
    0x1877B51E57A764D5ULL, 0xA2853B80F17F58EEULL, 0x993E1DE72D36D310ULL,
    0xB3598080CE64A656ULL, 0x252F59CF0D9F04BBULL, 0xD23C8E176D113600ULL,
    0x1BDA0492E7E4586EULL, 0x21E0BD5026C619BFULL, 0x3B097ADAF088F94EULL,
    0x8D14DEDB30BE846EULL, 0xF95CFFA23AF5F6F4ULL, 0x3871700761B3F743ULL,
    0xCA672B91E9E4FA16ULL, 0x64C8E531BFF53B55ULL, 0x241260ED4AD1E87DULL,
    0x106C09B972D2E822ULL, 0x7FBA195410E5CA30ULL, 0x7884D9BC6CB569D8ULL,
    0x0647DFEDCD894A29ULL, 0x63573FF03E224774ULL, 0x4FC8E9560F91B123ULL,
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    0x443F64EC5A371195ULL, 0x4112CF68649A260EULL, 0xD813F2FAB7F5C5CAULL,
    0x660D3257380841EEULL, 0x59AC2C7873F910A3ULL, 0xE846963877671A17ULL,
    0x93B633ABFA3469F8ULL, 0xC0C0F5A60EF4CDCFULL, 0xCAF21ECD4377B28CULL,
    0x57277707199B8175ULL, 0x506C11B9D90E8B1DULL, 0xD83CC2687A19255FULL,
    0x4A29C6465A314CD1ULL, 0xED2DF21216235097ULL, 0xB5635C95FF7296E2ULL,
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    0x944F6DE09134DFB6ULL, 0x6C47BEC883A7DE39ULL, 0x6AD047C430A12104ULL,
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    0x9338E69C052B8E7BULL, 0x455A4B4CFE30E3F5ULL, 0x6B02E63195AD0CF8ULL,
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    0x6DC93D9526A50E68ULL, 0xEE97F453F06791EDULL, 0x32AB0EDB696703D3ULL,
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    0x371F77E76BB8417EULL, 0x6BFA9AAE5EC05779ULL, 0xCD04F3FF001A4778ULL,
    0xE3273522064480CAULL, 0x9F91508BFFCFC14AULL, 0x049A7F41061A9E60ULL,
    0xFCB6BE43A9F2FE9BULL, 0x08DE8A1C7797DA9BULL, 0x8F9887E6078735A1ULL,
    0xB5B4071DBFC73A66ULL, 0x230E343DFBA08D33ULL, 0x43ED7F5A0FAE657DULL,
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    0x53C065C6C8E63528ULL, 0xE34A1D250E7A8D6BULL, 0xD6B04D3B7651DD7EULL,
    0x5E90277E7CB39E2DULL, 0x2C046F22062DC67DULL, 0xB10BB459132D0A26ULL,
    0x3FA9DDFB67E2F199ULL, 0x0E09B88E1914F7AFULL, 0x10E8B35AF3EEAB37ULL,
    0x9EEDECA8E272B933ULL, 0xD4C718BC4AE8AE5FULL, 0x81536D601170FC20ULL,
    0x91B534F885818A06ULL, 0xEC8177F83F900978ULL, 0x190E714FADA5156EULL,
    0xB592BF39B0364963ULL, 0x89C350C893AE7DC1ULL, 0xAC042E70F8B383F2ULL,
    0xB49B52E587A1EE60ULL, 0xFB152FE3FF26DA89ULL, 0x3E666E6F69AE2C15ULL,
    0x3B544EBE544C19F9ULL, 0xE805A1E290CF2456ULL, 0x24B33C9D7ED25117ULL,
    0xE74733427B72F0C1ULL, 0x0A804D18B7097475ULL, 0x57E3306D881EDB4FULL,
    0x4AE7D6A36EB5DBCBULL, 0x2D8D5432157064C8ULL, 0xD1E649DE1E7F268BULL,
    0x8A328A1CEDFE552CULL, 0x07A3AEC79624C7DAULL, 0x84547DDC3E203C94ULL,
    0x990A98FD5071D263ULL, 0x1A4FF12616EEFC89ULL, 0xF6F7FD1431714200ULL,
    0x30C05B1BA332F41CULL, 0x8D2636B81555A786ULL, 0x46C9FEB55D120902ULL,
    0xCCEC0A73B49C9921ULL, 0x4E9D2827355FC492ULL, 0x19EBB029435DCB0FULL,
    0x4659D2B743848A2CULL, 0x963EF2C96B33BE31ULL, 0x74F85198B05A2E7DULL,
    0x5A0F544DD2B1FB18ULL, 0x03727073C2E134B1ULL, 0xC7F6AA2DE59AEA61ULL,
    0x352787BAA0D7C22FULL, 0x9853EAB63B5E0B35ULL, 0xABBDCDD7ED5C0860ULL,
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    0x4E4B705B92903BA4ULL, 0xFF577222C14F0A3AULL, 0x55B6344CF97AAFAEULL,
    0xB862225B055B6960ULL, 0xCAC09AFBDDD2CDB4ULL, 0xDAF8E9829FE96B5FULL,
    0xB5FDFC5D3132C498ULL, 0x310CB380DB6F7503ULL, 0xE87FBB46217A360EULL,
    0x2102AE466EBB1148ULL, 0xF8549E1A3AA5E00DULL, 0x07A69AFDCC42261AULL,
    0xC4C118BFE78FEAAEULL, 0xF9F4892ED96BD438ULL, 0x1AF3DBE25D8F45DAULL,
    0xF5B4B0B0D2DEEEB4ULL, 0x962ACEEFA82E1C84ULL, 0x046E3ECAAF453CE9ULL,
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    0xD586BD01C5C217F6ULL, 0x5E5637885F29BC2BULL, 0x7EBA726D8C94094BULL,
    0x0A56A5F0BFE39272ULL, 0xD79476A84EE20D06ULL, 0x9E4C1269BAA4BF37ULL,
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    0x56986E2EF3ED091BULL, 0x917F1DD5F8886C61ULL, 0xD20D8C88C8FFE65FULL,
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    0x1EF6E6DBB1961EC9ULL, 0x70CC73D90BC26E24ULL, 0xE21A6B35DF0C3AD7ULL,
    0x003A93D8B2806962ULL, 0x1C99DED33CB890A1ULL, 0xCF3145DE0ADD4289ULL,
    0xD0E4427A5514FB72ULL, 0x77C621CC9FB3A483ULL, 0x67A34DAC4356550BULL,
    0xF8D626AAAF278509ULL
  };


  /// Indices to the Random64[] array

  const int RandomPiece     = 0;
  const int RandomCastle    = 768;
  const int RandomEnPassant = 772;
  const int RandomTurn      = 780;


  /// Prototypes

  uint64_t book_key(const Position& pos);
  uint64_t book_piece_key(Piece p, Square s);
  uint64_t book_castle_key(const Position& pos);
  uint64_t book_ep_key(const Position& pos);
  uint64_t book_color_key(const Position& pos);
}


////
//// Functions
////


/// Destructor. Be sure file is closed before we leave.

Book::~Book() {

  close();
}


/// Book::open() opens a book file with a given file name

void Book::open(const string& fName) {

  // Close old file before opening the new
  close();

  fileName = fName;
  ifstream::open(fileName.c_str(), ifstream::in | ifstream::binary);
  if (!is_open())
      return;

  // Get the book size in number of entries
  seekg(0, ios::end);
  bookSize = tellg() / EntrySize;
  seekg(0, ios::beg);

  if (!good())
  {
      cerr << "Failed to open book file " << fileName << endl;
      Application::exit_with_failure();
  }
}


/// Book::close() closes the file only if it is open, otherwise
/// we can end up in a little mess due to how std::ifstream works.

void Book::close() {

  if (is_open())
      ifstream::close();
}


/// Book::file_name() returns the file name of the currently active book,
/// or the empty string if no book is open.

const string Book::file_name() const {

  return is_open() ? fileName : "";
}


/// Book::get_move() gets a book move for a given position. Returns
/// MOVE_NONE if no book move is found.

Move Book::get_move(const Position& pos) {

  if (!is_open() || bookSize == 0)
      return MOVE_NONE;

  int bookMove = 0, scoresSum = 0;
  uint64_t key = book_key(pos);
  BookEntry entry;

  // Choose a book move among the possible moves for the given position
  for (int idx = find_key(key); idx < bookSize; idx++)
  {
      read_entry(entry, idx);
      if (entry.key != key)
          break;

      int score = entry.count;

      assert(score > 0);

      // Choose book move according to its score. If a move has a very
      // high score it has more probability to be choosen then a one with
      // lower score. Note that first entry is always chosen.
      scoresSum += score;
      if (int(genrand_int32() % scoresSum) < score)
          bookMove = entry.move;
  }
  if (!bookMove)
      return MOVE_NONE;

  MoveStack mlist[256];
  MoveStack* last = generate_moves(pos, mlist);
  for (MoveStack* cur = mlist; cur != last; cur++)
      if ((int(cur->move) & 07777) == bookMove)
          return cur->move;

  return MOVE_NONE;
}


/// Book::find_key() takes a book key as input, and does a binary search
/// through the book file for the given key. The index to the first book
/// entry with the same key as the input is returned. When the key is not
/// found in the book file, bookSize is returned.

int Book::find_key(uint64_t key) {

  int left, right, mid;
  BookEntry entry;

  // Binary search (finds the leftmost entry)
  left = 0;
  right = bookSize - 1;

  assert(left <= right);

  while (left < right)
  {
      mid = (left + right) / 2;

      assert(mid >= left && mid < right);

      read_entry(entry, mid);
      if (key <= entry.key)
          right = mid;
      else
          left = mid + 1;
  }

  assert(left == right);

  read_entry(entry, left);
  return (entry.key == key)? left : bookSize;
}


/// Book::read_entry() takes a BookEntry reference and an integer index as
/// input, and looks up the opening book entry at the given index in the book
/// file. The book entry is copied to the first input parameter.

void Book::read_entry(BookEntry& entry, int idx) {

  assert(idx >= 0 && idx < bookSize);
  assert(is_open());

  seekg(idx * EntrySize, ios_base::beg);
  *this >> entry;
  if (!good())
  {
      cerr << "Failed to read book entry at index " << idx << endl;
      Application::exit_with_failure();
  }
}


/// Book::read_integer() reads size chars from the file stream
/// and converts them in an integer number.

uint64_t Book::read_integer(int size) {

  char buf[8];
  read(buf, size);

  // Numbers are stored on disk as a binary byte stream
  uint64_t n = 0ULL;
  for (int i = 0; i < size; i++)
      n = (n << 8) + (unsigned char)buf[i];

  return n;
}


////
//// Local definitions
////

namespace {

  uint64_t book_key(const Position& pos) {

    uint64_t result = 0ULL;

    for (Color c = WHITE; c <= BLACK; c++)
    {
        Bitboard b = pos.pieces_of_color(c);

        while (b)
        {
            Square s = pop_1st_bit(&b);
            Piece p = pos.piece_on(s);

            assert(piece_is_ok(p));
            assert(color_of_piece(p) == c);

            result ^= book_piece_key(p, s);
        }
    }
    result ^= book_castle_key(pos);
    result ^= book_ep_key(pos);
    result ^= book_color_key(pos);
    return result;
  }


  uint64_t book_piece_key(Piece p, Square s) {

    /// Convert pieces to the range 0..11
    static const int PieceTo12[] = { 0, 0, 2, 4, 6, 8, 10, 0, 0, 1, 3, 5, 7, 9, 11 };

    return Random64[RandomPiece + (PieceTo12[int(p)]^1) * 64 + int(s)];
  }


  uint64_t book_castle_key(const Position& pos) {

    uint64_t result = 0ULL;

    if (pos.can_castle_kingside(WHITE))
        result ^= Random64[RandomCastle+0];

    if (pos.can_castle_queenside(WHITE))
        result ^= Random64[RandomCastle+1];

    if (pos.can_castle_kingside(BLACK))
        result ^= Random64[RandomCastle+2];

    if (pos.can_castle_queenside(BLACK))
        result ^= Random64[RandomCastle+3];

    return result;
  }


  uint64_t book_ep_key(const Position& pos) {
    return (pos.ep_square() == SQ_NONE ? 0ULL : Random64[RandomEnPassant + square_file(pos.ep_square())]);
  }


  uint64_t book_color_key(const Position& pos) {
    return (pos.side_to_move() == WHITE ? Random64[RandomTurn] : 0ULL);
  }
}
