Weighted Random

Weighted random selection — pick a key from a weighted map with probability proportional to each entry’s float weight.
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RandomUtils (GS_Core::RandomUtils) provides a single templated static method for weighted random selection from a map. The caller provides their own AZ::SimpleLcgRandom instance for deterministic control over the random sequence.

Used by: RandomNodeData (dialogue random node), KlattVoiceComponent (phoneme selection), any system needing weighted random draws.

For usage guides and setup examples, see The Basics: GS_Core.

 

Contents

API Reference

template<typename T>
static T GetRandomWeighted(
    AZ::SimpleLcgRandom* rand,
    const AZStd::unordered_map<T, float>& weightedTable
);

Selects one key from weightedTable with probability proportional to its float weight value. Higher weights mean higher probability of selection.

ParameterDescription
randCaller-owned AZ::SimpleLcgRandom instance. The caller controls seeding and lifetime.
weightedTableMap of candidates to weights. Keys are the items to select from; values are their relative weights.

Returns: The selected key of type T.

Edge cases:

  • Falls back to the last entry on floating-point precision edge cases.
  • Asserts if weightedTable is empty.

Usage Example

#include <GS_Core/Utility/Random/RandomUtils.h>
#include <AzCore/Math/Random.h>

// Member field — keep the random instance alive across calls
AZ::SimpleLcgRandom m_random;

// Build a weighted table: key = item, value = relative weight
AZStd::unordered_map<AZStd::string, float> lootTable;
lootTable["Common Sword"]    = 50.0f;
lootTable["Rare Shield"]     = 30.0f;
lootTable["Epic Helmet"]     = 15.0f;
lootTable["Legendary Ring"]  =  5.0f;

// Select an item — "Common Sword" is 10x more likely than "Legendary Ring"
AZStd::string selected = GS_Core::RandomUtils::GetRandomWeighted(&m_random, lootTable);

See Also

For related resources:

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