/** Optimized version of GetValueEstimate() if RAVE and not other
estimators are used.
Previously there were more estimators than move value and RAVE value,
and in the future there may be again. GetValueEstimate() is easier to
extend, this function is more optimized for the special case. */
SgUctValue SgUctSearch::GetValueEstimateRave(const SgUctNode& child) const
{
SG_ASSERT(m_rave);
SgUctValue value;
SgUctStatistics uctStats;
if (child.HasMean())
{
uctStats.Initialize(child.Mean(), child.MoveCount());
}
SgUctStatistics raveStats;
if (child.HasRaveValue())
{
raveStats.Initialize(child.RaveValue(), child.RaveCount());
}
int virtualLossCount = child.VirtualLossCount();
if (virtualLossCount > 0)
{
uctStats.Add(InverseEstimate(0), SgUctValue(virtualLossCount));
raveStats.Add(0, SgUctValue(virtualLossCount));
}
bool hasRave = raveStats.IsDefined();
if (uctStats.IsDefined())
{
SgUctValue moveValue = InverseEstimate((SgUctValue)uctStats.Mean());
if (hasRave)
{
SgUctValue moveCount = uctStats.Count();
SgUctValue raveCount = raveStats.Count();
SgUctValue weight =
raveCount
/ (moveCount
* (m_raveWeightParam1 + m_raveWeightParam2 * raveCount)
+ raveCount);
value = weight * raveStats.Mean() + (1.f - weight) * moveValue;
}
else
{
// This can happen only in lock-free multi-threading. Normally,
// each move played in a position should also cause a RAVE value
// to be added. But in lock-free multi-threading it can happen
// that the move value was already updated but the RAVE value not
SG_ASSERT(m_numberThreads > 1 && m_lockFree);
value = moveValue;
}
}
else if (hasRave)
value = raveStats.Mean();
else
value = m_firstPlayUrgency;
SG_ASSERT(m_numberThreads > 1
|| fabs(value - GetValueEstimate(m_rave, child)) < 1e-3/*epsilon*/);
return value;
}
SgUctValue SgUctSearch::GetValueEstimate(bool useRave, const SgUctNode& child) const
{
SgUctValue value = 0;
SgUctValue weightSum = 0;
bool hasValue = false;
SgUctStatistics uctStats;
if (child.HasMean())
{
uctStats.Initialize(child.Mean(), child.MoveCount());
}
int virtualLossCount = child.VirtualLossCount();
if (virtualLossCount > 0)
{
uctStats.Add(InverseEstimate(0), SgUctValue(virtualLossCount));
}
if (uctStats.IsDefined())
{
SgUctValue weight = static_cast<SgUctValue>(uctStats.Count());
value += weight * InverseEstimate((SgUctValue)uctStats.Mean());
weightSum += weight;
hasValue = true;
}
if (useRave)
{
SgUctStatistics raveStats;
if (child.HasRaveValue())
{
raveStats.Initialize(child.RaveValue(), child.RaveCount());
}
if (virtualLossCount > 0)
{
raveStats.Add(0, SgUctValue(virtualLossCount));
}
if (raveStats.IsDefined())
{
SgUctValue raveCount = raveStats.Count();
SgUctValue weight =
raveCount
/ ( m_raveWeightParam1
+ m_raveWeightParam2 * raveCount
);
value += weight * raveStats.Mean();
weightSum += weight;
hasValue = true;
}
}
if (hasValue)
return value / weightSum;
else
return m_firstPlayUrgency;
}
