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Remove some difficult to understand C++11 constructs

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Code like this is more a case of showing off one's C++ knowledge, rather than
using it adequately, IMHO.

**First loop (std::generate)**

Iterators are inadequate here, because they lose the key information which is
idx. As a result, we need to carry a redundant idx variable, and increment it
along the way. Very clumsy.
Usage of std::generate and a lambda function only obfuscate the code, which is
merely a simple and stupid loop over the elements of a vector.

**Second loop (std::accumulate)**

This code is thoroughlly incomprehensible. Restore the original, which was much
simpler to understand.

**Third loop (range based loop)**

Again, a range based loop is inadequate, because we lose idx! To resolve this
artificially created problem, the data model was made redundant (idx is a data
member of db[] elements!?), which is ugly and unjustified. A simple and stupid
for loop with idx does the job much better.

No functional change.

Resolves #313
This commit is contained in:
lucasart 2015-03-27 09:44:57 +08:00 • committed by Joona Kiiski
parent 8463fa479e
commit 60beb18efc
1 changed files with 9 additions and 9 deletions
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18
src/bitbase.cpp
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@ -64,7 +64,6 @@ namespace {
template<Color Us> Result classify(const std::vector<KPKPosition>& db);
unsigned id;
Color us;
Square ksq[COLOR_NB], psq;
Result result;
@ -85,20 +84,22 @@ bool Bitbases::probe(Square wksq, Square wpsq, Square bksq, Color us) {
void Bitbases::init() {
std::vector<KPKPosition> db(MAX_INDEX);
unsigned id = 0;
unsigned idx, repeat = 1;
// Initialize db with known win / draw positions
std::generate(db.begin(), db.end(), [&id](){ return KPKPosition(id++); });
for (idx = 0; idx < MAX_INDEX; ++idx)
db[idx] = KPKPosition(idx);
// Iterate through the positions until none of the unknown positions can be
// changed to either wins or draws (15 cycles needed).
while (std::accumulate(db.begin(), db.end(), false, [&](bool repeat, KPKPosition& pos)
{ return (pos == UNKNOWN && pos.classify(db) != UNKNOWN) || repeat; })){}
while (repeat)
for (repeat = idx = 0; idx < MAX_INDEX; ++idx)
repeat |= (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN);
// Map 32 results into one KPKBitbase[] entry
for (auto& pos : db)
if (pos == WIN)
KPKBitbase[pos.id / 32] |= 1 << (pos.id & 0x1F);
for (idx = 0; idx < MAX_INDEX; ++idx)
if (db[idx] == WIN)
KPKBitbase[idx / 32] |= 1 << (idx & 0x1F);
}
@ -106,7 +107,6 @@ namespace {
KPKPosition::KPKPosition(unsigned idx) {
id = idx;
ksq[WHITE] = Square((idx >> 0) & 0x3F);
ksq[BLACK] = Square((idx >> 6) & 0x3F);
us = Color ((idx >> 12) & 0x01);