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Check tablebase files

This addresses partially issue #1911 in that it documents in our
Readme the command that users can use to verifying the md5sum of
their downloaded tablebase files.

Additionally, a quick check of the file size (the size of each
tablebase file modulo 64 is 16 as pointed out by @syzygy1) has been
implemented at launch time in Stockfish.

Closes official-stockfish#1927
and official-stockfish#1911

No functional change.
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vondele authored and snicolet committed Jan 3, 2019
1 parent 3c576ef commit bb843a00c1ef381162dc9c2491b5436b6cf5563f
Showing with 29 additions and 9 deletions.
  1. +3 −1 Readme.md
  2. +26 −8 src/syzygy/tbprobe.cpp
@@ -86,7 +86,9 @@ Currently, Stockfish has the following UCI options:
Example: `C:\tablebases\wdl345;C:\tablebases\wdl6;D:\tablebases\dtz345;D:\tablebases\dtz6`

It is recommended to store .rtbw files on an SSD. There is no loss in storing
the .rtbz files on a regular HD.
the .rtbz files on a regular HD. It is recommended to verify all md5 checksums
of the downloaded tablebase files (`md5sum -c checksum.md5`) as corruption will
lead to engine crashes.

* #### SyzygyProbeDepth
Minimum remaining search depth for which a position is probed. Set this option
@@ -214,14 +214,22 @@ class TBFile : public std::ifstream {
return *baseAddress = nullptr, nullptr;

fstat(fd, &statbuf);

if (statbuf.st_size % 64 != 16)
{
std::cerr << "Corrupt tablebase file " << fname << std::endl;
exit(EXIT_FAILURE);
}

*mapping = statbuf.st_size;
*baseAddress = mmap(nullptr, statbuf.st_size, PROT_READ, MAP_SHARED, fd, 0);
madvise(*baseAddress, statbuf.st_size, MADV_RANDOM);
::close(fd);

if (*baseAddress == MAP_FAILED) {
if (*baseAddress == MAP_FAILED)
{
std::cerr << "Could not mmap() " << fname << std::endl;
exit(1);
exit(EXIT_FAILURE);
}
#else
// Note FILE_FLAG_RANDOM_ACCESS is only a hint to Windows and as such may get ignored.
@@ -233,29 +241,39 @@ class TBFile : public std::ifstream {

DWORD size_high;
DWORD size_low = GetFileSize(fd, &size_high);

if (size_low % 64 != 16)
{
std::cerr << "Corrupt tablebase file " << fname << std::endl;
exit(EXIT_FAILURE);
}

HANDLE mmap = CreateFileMapping(fd, nullptr, PAGE_READONLY, size_high, size_low, nullptr);
CloseHandle(fd);

if (!mmap) {
if (!mmap)
{
std::cerr << "CreateFileMapping() failed" << std::endl;
exit(1);
exit(EXIT_FAILURE);
}

*mapping = (uint64_t)mmap;
*baseAddress = MapViewOfFile(mmap, FILE_MAP_READ, 0, 0, 0);

if (!*baseAddress) {
if (!*baseAddress)
{
std::cerr << "MapViewOfFile() failed, name = " << fname
<< ", error = " << GetLastError() << std::endl;
exit(1);
exit(EXIT_FAILURE);
}
#endif
uint8_t* data = (uint8_t*)*baseAddress;

constexpr uint8_t Magics[][4] = { { 0xD7, 0x66, 0x0C, 0xA5 },
{ 0x71, 0xE8, 0x23, 0x5D } };

if (memcmp(data, Magics[type == WDL], 4)) {
if (memcmp(data, Magics[type == WDL], 4))
{
std::cerr << "Corrupted table in file " << fname << std::endl;
unmap(*baseAddress, *mapping);
return *baseAddress = nullptr, nullptr;
@@ -416,7 +434,7 @@ class TBTables {
}
}
std::cerr << "TB hash table size too low!" << std::endl;
exit(1);
exit(EXIT_FAILURE);
}

public:

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