// Denominator, which is a constant value.
static const uint32_t D = 1u << 31;
+ static const uint32_t UnknownN = UINT32_MAX;
// Construct a BranchProbability with only numerator assuming the denominator
// is 1<<31. For internal use only.
explicit BranchProbability(uint32_t n) : N(n) {}
public:
- BranchProbability() : N(0) {}
+ BranchProbability() : N(UnknownN) {}
BranchProbability(uint32_t Numerator, uint32_t Denominator);
bool isZero() const { return N == 0; }
+ bool isUnknown() const { return N == UnknownN; }
static BranchProbability getZero() { return BranchProbability(0); }
static BranchProbability getOne() { return BranchProbability(D); }
+ static BranchProbability getUnknown() { return BranchProbability(UnknownN); }
// Create a BranchProbability object with the given numerator and 1<<31
// as denominator.
static BranchProbability getRaw(uint32_t N) { return BranchProbability(N); }
+ // Create a BranchProbability object from 64-bit integers.
+ static BranchProbability getBranchProbability(uint64_t Numerator,
+ uint64_t Denominator);
// Normalize given probabilties so that the sum of them becomes approximate
// one.
- template <class ProbabilityList>
- static void normalizeProbabilities(ProbabilityList &Probs);
+ template <class ProbabilityIter>
+ static void normalizeProbabilities(ProbabilityIter Begin,
+ ProbabilityIter End);
// Normalize a list of weights by scaling them down so that the sum of them
// doesn't exceed UINT32_MAX.
uint64_t scaleByInverse(uint64_t Num) const;
BranchProbability &operator+=(BranchProbability RHS) {
- assert(N <= D - RHS.N &&
- "The sum of branch probabilities should not exceed one!");
- N += RHS.N;
+ assert(N != UnknownN && RHS.N != UnknownN &&
+ "Unknown probability cannot participate in arithmetics.");
+ // Saturate the result in case of overflow.
+ N = (uint64_t(N) + RHS.N > D) ? D : N + RHS.N;
return *this;
}
BranchProbability &operator-=(BranchProbability RHS) {
- assert(N >= RHS.N &&
- "Can only subtract a smaller probability from a larger one!");
- N -= RHS.N;
+ assert(N != UnknownN && RHS.N != UnknownN &&
+ "Unknown probability cannot participate in arithmetics.");
+ // Saturate the result in case of underflow.
+ N = N < RHS.N ? 0 : N - RHS.N;
return *this;
}
BranchProbability &operator*=(BranchProbability RHS) {
+ assert(N != UnknownN && RHS.N != UnknownN &&
+ "Unknown probability cannot participate in arithmetics.");
N = (static_cast<uint64_t>(N) * RHS.N + D / 2) / D;
return *this;
}
+ BranchProbability &operator/=(uint32_t RHS) {
+ assert(N != UnknownN &&
+ "Unknown probability cannot participate in arithmetics.");
+ assert(RHS > 0 && "The divider cannot be zero.");
+ N /= RHS;
+ return *this;
+ }
+
BranchProbability operator+(BranchProbability RHS) const {
BranchProbability Prob(*this);
return Prob += RHS;
return Prob *= RHS;
}
+ BranchProbability operator/(uint32_t RHS) const {
+ BranchProbability Prob(*this);
+ return Prob /= RHS;
+ }
+
bool operator==(BranchProbability RHS) const { return N == RHS.N; }
bool operator!=(BranchProbability RHS) const { return !(*this == RHS); }
- bool operator<(BranchProbability RHS) const { return N < RHS.N; }
- bool operator>(BranchProbability RHS) const { return RHS < *this; }
- bool operator<=(BranchProbability RHS) const { return !(RHS < *this); }
- bool operator>=(BranchProbability RHS) const { return !(*this < RHS); }
+
+ bool operator<(BranchProbability RHS) const {
+ assert(N != UnknownN && RHS.N != UnknownN &&
+ "Unknown probability cannot participate in comparisons.");
+ return N < RHS.N;
+ }
+
+ bool operator>(BranchProbability RHS) const {
+ assert(N != UnknownN && RHS.N != UnknownN &&
+ "Unknown probability cannot participate in comparisons.");
+ return RHS < *this;
+ }
+
+ bool operator<=(BranchProbability RHS) const {
+ assert(N != UnknownN && RHS.N != UnknownN &&
+ "Unknown probability cannot participate in comparisons.");
+ return !(RHS < *this);
+ }
+
+ bool operator>=(BranchProbability RHS) const {
+ assert(N != UnknownN && RHS.N != UnknownN &&
+ "Unknown probability cannot participate in comparisons.");
+ return !(*this < RHS);
+ }
};
inline raw_ostream &operator<<(raw_ostream &OS, BranchProbability Prob) {
return Prob.print(OS);
}
-template <class ProbabilityList>
-void BranchProbability::normalizeProbabilities(ProbabilityList &Probs) {
- uint64_t Sum = 0;
- for (auto Prob : Probs)
- Sum += Prob.N;
- assert(Sum > 0);
- for (auto &Prob : Probs)
- Prob.N = (Prob.N * uint64_t(D) + Sum / 2) / Sum;
+template <class ProbabilityIter>
+void BranchProbability::normalizeProbabilities(ProbabilityIter Begin,
+ ProbabilityIter End) {
+ if (Begin == End)
+ return;
+
+ unsigned UnknownProbCount = 0;
+ uint64_t Sum = std::accumulate(Begin, End, uint64_t(0),
+ [&](uint64_t S, const BranchProbability &BP) {
+ if (!BP.isUnknown())
+ return S + BP.N;
+ UnknownProbCount++;
+ return S;
+ });
+
+ if (UnknownProbCount > 0) {
+ BranchProbability ProbForUnknown = BranchProbability::getZero();
+ // If the sum of all known probabilities is less than one, evenly distribute
+ // the complement of sum to unknown probabilities. Otherwise, set unknown
+ // probabilities to zeros and continue to normalize known probabilities.
+ if (Sum < BranchProbability::getDenominator())
+ ProbForUnknown = BranchProbability::getRaw(
+ (BranchProbability::getDenominator() - Sum) / UnknownProbCount);
+
+ std::replace_if(Begin, End,
+ [](const BranchProbability &BP) { return BP.isUnknown(); },
+ ProbForUnknown);
+
+ if (Sum <= BranchProbability::getDenominator())
+ return;
+ }
+
+ if (Sum == 0) {
+ BranchProbability BP(1, std::distance(Begin, End));
+ std::fill(Begin, End, BP);
+ return;
+ }
+
+ for (auto I = Begin; I != End; ++I)
+ I->N = (I->N * uint64_t(D) + Sum / 2) / Sum;
}
template <class WeightListIter>
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