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Implementing Parallel search algorithm ABDADA #95
New TranspositionTableEntry type, concurrent read for ABDADA
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,98 @@ | ||
| package ai | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "github.com/Vadman97/ChessAI3/pkg/chessai/board" | ||
| "github.com/Vadman97/ChessAI3/pkg/chessai/color" | ||
| "github.com/Vadman97/ChessAI3/pkg/chessai/location" | ||
| "github.com/Vadman97/ChessAI3/pkg/chessai/transposition_table" | ||
| "time" | ||
| ) | ||
|
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| func (ab *ABDADA) ABDADA(root *board.Board, depth, alpha, beta int, exclusiveProbe bool, currentPlayer color.Color, previousMove *board.LastMove) *ScoredMove { | ||
| if depth == 0 { | ||
| return &ScoredMove{ | ||
| Score: ab.player.EvaluateBoard(root, ab.player.PlayerColor).TotalScore, | ||
| } | ||
| } else { | ||
| var best ScoredMove | ||
|
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| answerChan := ab.asyncTTRead(root, uint16(depth), alpha, beta, currentPlayer, exclusiveProbe) | ||
| // generate moves while waiting for the answer ... | ||
| moves := root.GetAllMoves(currentPlayer, previousMove) | ||
|
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| // block and grab the answer | ||
| ttAnswer := <-answerChan | ||
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| } | ||
| } | ||
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| type ABDADA struct { | ||
| player *AIPlayer | ||
| currentSearchDepth int | ||
| lastSearchDepth int | ||
| lastSearchTime time.Duration | ||
| } | ||
|
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| func (ab *ABDADA) GetName() string { | ||
| return fmt.Sprintf("%s,[D:%d;T:%s]", AlgorithmABDADA, ab.lastSearchDepth, ab.lastSearchTime) | ||
| } | ||
|
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| func (ab *ABDADA) GetBestMove(p *AIPlayer, b *board.Board, previousMove *board.LastMove) *ScoredMove { | ||
| ab.player = p | ||
| } | ||
|
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| type TTAnswer struct { | ||
| alpha, beta, score int | ||
| bestMove location.Move | ||
| onEvaluation bool | ||
| } | ||
|
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| func (ab *ABDADA) asyncTTRead(root *board.Board, depth uint16, alpha, beta int, currentPlayer color.Color, exclusiveProbe bool) chan TTAnswer { | ||
| answerChan := make(chan TTAnswer) | ||
| go func(answerChan chan TTAnswer) { | ||
| answer := TTAnswer{ | ||
| alpha: alpha, | ||
| beta: beta, | ||
| score: NegInf, | ||
| } | ||
| if ab.player.TranspositionTableEnabled { | ||
| // transposition table lookup | ||
| h := root.Hash() | ||
| if e, ok := ab.player.alphaBetaTable.Read(&h, currentPlayer); ok { | ||
| entry := e.(*transposition_table.TranspositionTableEntryABDADA) | ||
| entry.Lock.Lock() | ||
|
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| if entry.Depth == depth && exclusiveProbe && entry.NumProcessors > 0 { | ||
| answer.onEvaluation = true | ||
| } else if entry.Depth >= depth { | ||
| if entry.EntryType == transposition_table.TrueScore { | ||
| answer.score = entry.Score | ||
| answer.alpha = entry.Score | ||
| answer.beta = entry.Score | ||
| } else if entry.EntryType == transposition_table.UpperBound && entry.Score < beta { | ||
| answer.score = entry.Score | ||
| answer.beta = entry.Score | ||
| } else if entry.EntryType == transposition_table.LowerBound && entry.Score > alpha { | ||
| answer.score = entry.Score | ||
| answer.alpha = entry.Score | ||
| } | ||
|
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| if entry.Depth == depth && answer.alpha < answer.beta { | ||
| // Increment the number of processors evaluating this node | ||
| entry.NumProcessors++ | ||
| } | ||
| } else { | ||
| // This is the first processor to evaluate this node | ||
| entry.Depth = depth | ||
| entry.EntryType = transposition_table.Unset | ||
| entry.NumProcessors = 1 | ||
| } | ||
|
|
||
| entry.Lock.Unlock() | ||
| } | ||
| } | ||
| answerChan <- answer | ||
| }(answerChan) | ||
| return answerChan | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,83 @@ | ||
| package transposition_table | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "github.com/Vadman97/ChessAI3/pkg/chessai/location" | ||
| "github.com/Vadman97/ChessAI3/pkg/chessai/util" | ||
| "sync" | ||
| ) | ||
|
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| type TranspositionTableEntryABMemory struct { | ||
| Lower, Upper int | ||
| BestMove location.Move | ||
| } | ||
|
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| const ( | ||
| Unset = byte(iota) | ||
| UpperBound = byte(iota) | ||
| LowerBound = byte(iota) | ||
| TrueScore = byte(iota) | ||
| ) | ||
|
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| type TranspositionTableEntryABDADA struct { | ||
| Score int | ||
| BestMove location.Move | ||
|
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| // Flag that identifies the entry | ||
| EntryType byte | ||
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| // Length of subtree upon which score is based. | ||
| Depth uint16 | ||
|
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| // The number of processors currently evaluating the node related to the transposition table entry | ||
| NumProcessors uint16 | ||
|
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| Lock sync.Mutex | ||
| } | ||
|
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| type TranspositionTable struct { | ||
| entryMap map[util.BoardHash]map[byte]interface{} | ||
| numStored int | ||
| numReads, numHits int | ||
| } | ||
|
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| func NewTranspositionTable() *TranspositionTable { | ||
| var m TranspositionTable | ||
| if m.entryMap == nil { | ||
| m.entryMap = make(map[util.BoardHash]map[byte]interface{}) | ||
| } | ||
| return &m | ||
| } | ||
|
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| /* | ||
| Note: Transposition table does not support concurrent read/write at the moment | ||
| */ | ||
| func (m *TranspositionTable) Store(hash *util.BoardHash, currentTurn byte, entry interface{}) { | ||
| _, ok := m.entryMap[*hash] | ||
| if !ok { | ||
| m.entryMap[*hash] = make(map[byte]interface{}) | ||
| } | ||
| m.entryMap[*hash][currentTurn] = entry | ||
| m.numStored++ | ||
| } | ||
|
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| func (m *TranspositionTable) Read(hash *util.BoardHash, currentTurn byte) (interface{}, bool) { | ||
| m.numReads++ | ||
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| m1, ok := m.entryMap[*hash] | ||
| if ok { | ||
| v, ok := m1[currentTurn] | ||
| if ok { | ||
| m.numHits++ | ||
| return v, true | ||
| } | ||
| } | ||
| return nil, false | ||
| } | ||
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| func (m *TranspositionTable) PrintMetrics() (result string) { | ||
| result += fmt.Sprintf("\tTotal entries in transposition table %d\n", m.numStored) | ||
| result += fmt.Sprintf("\tHit ratio %f%% (%d/%d)\n", 100.0*float64(m.numHits)/float64(m.numReads), | ||
| m.numHits, m.numReads) | ||
| return | ||
| } |
43 changes: 43 additions & 0 deletions
43
pkg/chessai/transposition_table/transposition_table_test.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,43 @@ | ||
| package transposition_table | ||
|
|
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| import ( | ||
| "github.com/Vadman97/ChessAI3/pkg/chessai/board" | ||
| "github.com/Vadman97/ChessAI3/pkg/chessai/color" | ||
| "github.com/stretchr/testify/assert" | ||
| "testing" | ||
| ) | ||
|
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| func TestTranspositionTable_StoreUpdateReadABDADA(t *testing.T) { | ||
| tt := NewTranspositionTable() | ||
|
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| b := board.Board{} | ||
| b.ResetDefault() | ||
| b.RandomizeIllegal() | ||
| h := b.Hash() | ||
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| ttEntry := TranspositionTableEntryABDADA{} | ||
| tt.Store(&h, color.Black, &ttEntry) | ||
| ttEntry.NumProcessors++ | ||
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| assert.Equal(t, uint16(1), ttEntry.NumProcessors) | ||
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| e, _ := tt.Read(&h, color.Black) | ||
| readEntry := e.(*TranspositionTableEntryABDADA) | ||
|
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| assert.Equal(t, uint16(1), readEntry.NumProcessors) | ||
| readEntry.NumProcessors++ | ||
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| assert.Equal(t, uint16(2), readEntry.NumProcessors) | ||
| assert.Equal(t, uint16(2), ttEntry.NumProcessors) | ||
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| newEntry := TranspositionTableEntryABDADA{} | ||
| tt.Store(&h, color.Black, &newEntry) | ||
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| assert.Equal(t, uint16(2), readEntry.NumProcessors) | ||
| assert.Equal(t, uint16(2), ttEntry.NumProcessors) | ||
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| e, _ = tt.Read(&h, color.Black) | ||
| readEntry = e.(*TranspositionTableEntryABDADA) | ||
|
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| assert.Equal(t, uint16(0), readEntry.NumProcessors) | ||
| } |
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