Browse Source

Rm functions related to Old AddBatch

master
arnaucube 3 years ago
parent
commit
d16ebd0c80
4 changed files with 210 additions and 1075 deletions
  1. +0
    -821
      addbatch.go
  2. +43
    -191
      addbatch_test.go
  3. +71
    -0
      tree.go
  4. +96
    -63
      vt.go

+ 0
- 821
addbatch.go

@ -1,821 +0,0 @@
package arbo
import (
"bytes"
"fmt"
"math"
"runtime"
"sort"
"sync"
"github.com/iden3/go-merkletree/db"
)
/*
AddBatch design
===============
CASE A: Empty Tree --> if tree is empty (root==0)
=================================================
- Build the full tree from bottom to top (from all the leaf to the root)
CASE B: ALMOST CASE A, Almost empty Tree --> if Tree has numLeafs < minLeafsThreshold
==============================================================================
- Get the Leafs (key & value) (iterate the tree from the current root getting
the leafs)
- Create a new empty Tree
- Do CASE A for the new Tree, giving the already existing key&values (leafs)
from the original Tree + the new key&values to be added from the AddBatch call
R R
/ \ / \
A * / \
/ \ / \
B C * *
/ | / \
/ | / \
/ | / \
L: A B G D
/ \
/ \
/ \
C *
/ \
/ \
/ \
... ... (nLeafs < minLeafsThreshold)
CASE C: ALMOST CASE B --> if Tree has few Leafs (but numLeafs>=minLeafsThreshold)
==============================================================================
- Use A, B, G, F as Roots of subtrees
- Do CASE B for each subtree
- Then go from L to the Root
R
/ \
/ \
/ \
* *
/ | / \
/ | / \
/ | / \
L: A B G D
/ \
/ \
/ \
C *
/ \
/ \
/ \
... ... (nLeafs >= minLeafsThreshold)
CASE D: Already populated Tree
==============================
- Use A, B, C, D as subtree
- Sort the Keys in Buckets that share the initial part of the path
- For each subtree add there the new leafs
R
/ \
/ \
/ \
* *
/ | / \
/ | / \
/ | / \
L: A B C D
/\ /\ / \ / \
... ... ... ... ... ...
CASE E: Already populated Tree Unbalanced
=========================================
- Need to fill M1 and M2, and then will be able to use CASE D
- Search for M1 & M2 in the inputed Keys
- Add M1 & M2 to the Tree
- From here can use CASE D
R
/ \
/ \
/ \
* *
| \
| \
| \
L: M1 * M2 * (where M1 and M2 are empty)
/ | /
/ | /
/ | /
A * *
/ \ | \
/ \ | \
/ \ | \
B * * C
/ \ |\
... ... | \
| \
D E
Algorithm decision
==================
- if nLeafs==0 (root==0): CASE A
- if nLeafs<minLeafsThreshold: CASE B
- if nLeafs>=minLeafsThreshold && (nLeafs/nBuckets) < minLeafsThreshold: CASE C
- else: CASE D & CASE E
- Multiple tree.Add calls: O(n log n)
- Used in: cases A, B, C
- Tree from bottom to top: O(log n)
- Used in: cases D, E
*/
const (
minLeafsThreshold = 100 // nolint:gomnd // TMP WIP this will be autocalculated
)
// AddBatch adds a batch of key-values to the Tree. Returns an array containing
// the indexes of the keys failed to add.
func (t *Tree) AddBatch(keys, values [][]byte) ([]int, error) {
t.updateAccessTime()
t.Lock()
defer t.Unlock()
vt, err := t.loadVT()
if err != nil {
return nil, err
}
invalids, err := vt.addBatch(keys, values)
if err != nil {
return nil, err
}
pairs, err := vt.computeHashes()
if err != nil {
return nil, err
}
t.root = vt.root.h
// store pairs in db
t.tx, err = t.db.NewTx()
if err != nil {
return nil, err
}
for i := 0; i < len(pairs); i++ {
if err := t.dbPut(pairs[i][0], pairs[i][1]); err != nil {
return nil, err
}
}
return t.finalizeAddBatch(len(keys), invalids)
}
// AddBatchOLD adds a batch of key-values to the Tree. Returns an array containing
// the indexes of the keys failed to add.
func (t *Tree) AddBatchOLD(keys, values [][]byte) ([]int, error) {
// TODO: support vaules=nil
t.updateAccessTime()
t.Lock()
defer t.Unlock()
kvs, err := t.keysValuesToKvs(keys, values)
if err != nil {
return nil, err
}
t.tx, err = t.db.NewTx()
if err != nil {
return nil, err
}
// if nCPU is not a power of two, cut at the highest power of two under
// nCPU
nCPU := flp2(runtime.NumCPU())
l := int(math.Log2(float64(nCPU)))
var invalids []int
// CASE A: if nLeafs==0 (root==0)
if bytes.Equal(t.root, t.emptyHash) {
invalids, err = t.caseA(nCPU, kvs)
if err != nil {
return nil, err
}
return t.finalizeAddBatch(len(keys), invalids)
}
// CASE B: if nLeafs<nBuckets
nLeafs, err := t.GetNLeafs()
if err != nil {
return nil, err
}
if nLeafs < minLeafsThreshold { // CASE B
invalids, err = t.caseB(nCPU, 0, kvs)
if err != nil {
return nil, err
}
return t.finalizeAddBatch(len(keys), invalids)
}
keysAtL, err := t.getKeysAtLevel(l + 1)
if err != nil {
return nil, err
}
// CASE C: if nLeafs>=minLeafsThreshold && (nLeafs/nBuckets) < minLeafsThreshold
// available parallelization, will need to be a power of 2 (2**n)
if nLeafs >= minLeafsThreshold &&
(nLeafs/nCPU) < minLeafsThreshold &&
len(keysAtL) == nCPU {
invalids, err = t.caseC(nCPU, l, keysAtL, kvs)
if err != nil {
return nil, err
}
return t.finalizeAddBatch(len(keys), invalids)
}
// CASE E
if len(keysAtL) != nCPU {
// CASE E: add one key at each bucket, and then do CASE D
buckets := splitInBuckets(kvs, nCPU)
kvs = []kv{}
for i := 0; i < len(buckets); i++ {
// add one leaf of the bucket, if there is an error when
// adding the k-v, try to add the next one of the bucket
// (until one is added)
var inserted int
for j := 0; j < len(buckets[i]); j++ {
if err := t.add(0, buckets[i][j].k, buckets[i][j].v); err == nil {
inserted = j
break
}
}
// put the buckets elements except the inserted one
kvs = append(kvs, buckets[i][:inserted]...)
kvs = append(kvs, buckets[i][inserted+1:]...)
}
keysAtL, err = t.getKeysAtLevel(l + 1)
if err != nil {
return nil, err
}
}
// CASE D
if len(keysAtL) == nCPU { // enter in CASE D if len(keysAtL)=nCPU, if not, CASE E
invalidsCaseD, err := t.caseD(nCPU, l, keysAtL, kvs)
if err != nil {
return nil, err
}
invalids = append(invalids, invalidsCaseD...)
return t.finalizeAddBatch(len(keys), invalids)
}
return nil, fmt.Errorf("UNIMPLEMENTED")
}
func (t *Tree) finalizeAddBatch(nKeys int, invalids []int) ([]int, error) {
// store root to db
if err := t.dbPut(dbKeyRoot, t.root); err != nil {
return nil, err
}
// update nLeafs
if err := t.incNLeafs(nKeys - len(invalids)); err != nil {
return nil, err
}
// commit db tx
if err := t.tx.Commit(); err != nil {
return nil, err
}
return invalids, nil
}
func (t *Tree) caseA(nCPU int, kvs []kv) ([]int, error) {
invalids, err := t.buildTreeFromLeafs(nCPU, kvs)
if err != nil {
return nil, err
}
return invalids, nil
}
func (t *Tree) caseB(nCPU, l int, kvs []kv) ([]int, error) {
// get already existing keys
aKs, aVs, err := t.getLeafs(t.root)
if err != nil {
return nil, err
}
aKvs, err := t.keysValuesToKvs(aKs, aVs)
if err != nil {
return nil, err
}
// add already existing key-values to the inputted key-values
// kvs = append(kvs, aKvs...)
kvs, invalids := combineInKVSet(aKvs, kvs)
// proceed with CASE A
sortKvs(kvs)
var invalids2 []int
if nCPU > 1 {
invalids2, err = t.buildTreeFromLeafs(nCPU, kvs)
if err != nil {
return nil, err
}
} else {
invalids2, err = t.buildTreeFromLeafsSingleThread(l, kvs)
if err != nil {
return nil, err
}
}
invalids = append(invalids, invalids2...)
return invalids, nil
}
func (t *Tree) caseC(nCPU, l int, keysAtL [][]byte, kvs []kv) ([]int, error) {
// 1. go down until level L (L=log2(nBuckets)): keysAtL
var excedents []kv
buckets := splitInBuckets(kvs, nCPU)
// 2. use keys at level L as roots of the subtrees under each one
subRoots := make([][]byte, nCPU)
dbgStatsPerBucket := make([]*dbgStats, nCPU)
txs := make([]db.Tx, nCPU)
var wg sync.WaitGroup
wg.Add(nCPU)
for i := 0; i < nCPU; i++ {
go func(cpu int) {
var err error
txs[cpu], err = t.db.NewTx()
if err != nil {
panic(err) // TODO WIP
}
if err := txs[cpu].Add(t.tx); err != nil {
panic(err) // TODO
}
bucketTree := Tree{tx: txs[cpu], db: t.db, maxLevels: t.maxLevels,
hashFunction: t.hashFunction, root: keysAtL[cpu],
emptyHash: t.emptyHash, dbg: newDbgStats()}
// 3. do CASE B (with 1 cpu) for each key at level L
_, err = bucketTree.caseB(1, l, buckets[cpu]) // TODO handle invalids
if err != nil {
panic(err) // TODO WIP
// return nil, err
}
subRoots[cpu] = bucketTree.root
dbgStatsPerBucket[cpu] = bucketTree.dbg
wg.Done()
}(i)
}
wg.Wait()
// merge buckets txs into Tree.tx
for i := 0; i < len(txs); i++ {
if err := t.tx.Add(txs[i]); err != nil {
return nil, err
}
}
// 4. go upFromKeys from the new roots of the subtrees
newRoot, err := t.upFromKeys(subRoots)
if err != nil {
return nil, err
}
t.root = newRoot
// add the key-values that have not been used yet
var invalids []int
for i := 0; i < len(excedents); i++ {
if err = t.add(0, excedents[i].k, excedents[i].v); err != nil {
invalids = append(invalids, excedents[i].pos)
}
}
for i := 0; i < len(dbgStatsPerBucket); i++ {
t.dbg.add(dbgStatsPerBucket[i])
}
return invalids, nil
}
func (t *Tree) caseD(nCPU, l int, keysAtL [][]byte, kvs []kv) ([]int, error) {
if nCPU == 1 { // CASE D, but with 1 cpu
var invalids []int
for i := 0; i < len(kvs); i++ {
if err := t.add(0, kvs[i].k, kvs[i].v); err != nil {
invalids = append(invalids, kvs[i].pos)
}
}
return invalids, nil
}
buckets := splitInBuckets(kvs, nCPU)
subRoots := make([][]byte, nCPU)
invalidsInBucket := make([][]int, nCPU)
dbgStatsPerBucket := make([]*dbgStats, nCPU)
txs := make([]db.Tx, nCPU)
var wg sync.WaitGroup
wg.Add(nCPU)
for i := 0; i < nCPU; i++ {
go func(cpu int) {
var err error
txs[cpu], err = t.db.NewTx()
if err != nil {
panic(err) // TODO WIP
}
// put already existing tx into txs[cpu], as txs[cpu]
// needs the pending key-values that are not in tree.db,
// but are in tree.tx
if err := txs[cpu].Add(t.tx); err != nil {
panic(err) // TODO WIP
}
bucketTree := Tree{tx: txs[cpu], db: t.db, maxLevels: t.maxLevels - l,
hashFunction: t.hashFunction, root: keysAtL[cpu],
emptyHash: t.emptyHash, dbg: newDbgStats()} // TODO bucketTree.dbg should be optional
for j := 0; j < len(buckets[cpu]); j++ {
if err = bucketTree.add(l, buckets[cpu][j].k, buckets[cpu][j].v); err != nil {
invalidsInBucket[cpu] = append(invalidsInBucket[cpu], buckets[cpu][j].pos)
}
}
subRoots[cpu] = bucketTree.root
dbgStatsPerBucket[cpu] = bucketTree.dbg
wg.Done()
}(i)
}
wg.Wait()
// merge buckets txs into Tree.tx
for i := 0; i < len(txs); i++ {
if err := t.tx.Add(txs[i]); err != nil {
return nil, err
}
}
newRoot, err := t.upFromKeys(subRoots)
if err != nil {
return nil, err
}
t.root = newRoot
var invalids []int
for i := 0; i < len(invalidsInBucket); i++ {
invalids = append(invalids, invalidsInBucket[i]...)
}
for i := 0; i < len(dbgStatsPerBucket); i++ {
t.dbg.add(dbgStatsPerBucket[i])
}
return invalids, nil
}
func splitInBuckets(kvs []kv, nBuckets int) [][]kv {
buckets := make([][]kv, nBuckets)
// 1. classify the keyvalues into buckets
for i := 0; i < len(kvs); i++ {
pair := kvs[i]
// bucketnum := keyToBucket(pair.k, nBuckets)
bucketnum := keyToBucket(pair.keyPath, nBuckets)
buckets[bucketnum] = append(buckets[bucketnum], pair)
}
return buckets
}
// TODO rename in a more 'real' name (calculate bucket from/for key)
func keyToBucket(k []byte, nBuckets int) int {
nLevels := int(math.Log2(float64(nBuckets)))
b := make([]int, nBuckets)
for i := 0; i < nBuckets; i++ {
b[i] = i
}
r := b
mid := len(r) / 2 //nolint:gomnd
for i := 0; i < nLevels; i++ {
if int(k[i/8]&(1<<(i%8))) != 0 {
r = r[mid:]
mid = len(r) / 2 //nolint:gomnd
} else {
r = r[:mid]
mid = len(r) / 2 //nolint:gomnd
}
}
return r[0]
}
type kv struct {
pos int // original position in the array
keyPath []byte
k []byte
v []byte
}
// compareBytes compares byte slices where the bytes are compared from left to
// right and each byte is compared by bit from right to left
func compareBytes(a, b []byte) bool {
// WIP
for i := 0; i < len(a); i++ {
for j := 0; j < 8; j++ {
aBit := a[i] & (1 << j)
bBit := b[i] & (1 << j)
if aBit > bBit {
return false
} else if aBit < bBit {
return true
}
}
}
return false
}
// sortKvs sorts the kv by path
func sortKvs(kvs []kv) {
sort.Slice(kvs, func(i, j int) bool {
return compareBytes(kvs[i].keyPath, kvs[j].keyPath)
})
}
func (t *Tree) keysValuesToKvs(ks, vs [][]byte) ([]kv, error) {
if len(ks) != len(vs) {
return nil, fmt.Errorf("len(keys)!=len(values) (%d!=%d)",
len(ks), len(vs))
}
kvs := make([]kv, len(ks))
for i := 0; i < len(ks); i++ {
keyPath := make([]byte, t.hashFunction.Len())
copy(keyPath[:], ks[i])
kvs[i].pos = i
kvs[i].keyPath = keyPath
kvs[i].k = ks[i]
kvs[i].v = vs[i]
}
return kvs, nil
}
/*
func (t *Tree) kvsToKeysValues(kvs []kv) ([][]byte, [][]byte) {
ks := make([][]byte, len(kvs))
vs := make([][]byte, len(kvs))
for i := 0; i < len(kvs); i++ {
ks[i] = kvs[i].k
vs[i] = kvs[i].v
}
return ks, vs
}
*/
// buildTreeFromLeafs splits the key-values into n Buckets (where n is the number
// of CPUs), in parallel builds a subtree for each bucket, once all the subtrees
// are built, uses the subtrees roots as keys for a new tree, which as result
// will have the complete Tree build from bottom to up, where until the
// log2(nCPU) level it has been computed in parallel.
func (t *Tree) buildTreeFromLeafs(nCPU int, kvs []kv) ([]int, error) {
l := int(math.Log2(float64(nCPU)))
buckets := splitInBuckets(kvs, nCPU)
subRoots := make([][]byte, nCPU)
invalidsInBucket := make([][]int, nCPU)
dbgStatsPerBucket := make([]*dbgStats, nCPU)
txs := make([]db.Tx, nCPU)
var wg sync.WaitGroup
wg.Add(nCPU)
for i := 0; i < nCPU; i++ {
go func(cpu int) {
sortKvs(buckets[cpu])
var err error
txs[cpu], err = t.db.NewTx()
if err != nil {
panic(err) // TODO
}
if err := txs[cpu].Add(t.tx); err != nil {
panic(err) // TODO
}
bucketTree := Tree{tx: txs[cpu], db: t.db, maxLevels: t.maxLevels,
hashFunction: t.hashFunction, root: t.emptyHash,
emptyHash: t.emptyHash, dbg: newDbgStats()}
currInvalids, err := bucketTree.buildTreeFromLeafsSingleThread(l, buckets[cpu])
if err != nil {
panic(err) // TODO
}
invalidsInBucket[cpu] = currInvalids
subRoots[cpu] = bucketTree.root
dbgStatsPerBucket[cpu] = bucketTree.dbg
wg.Done()
}(i)
}
wg.Wait()
// merge buckets txs into Tree.tx
for i := 0; i < len(txs); i++ {
if err := t.tx.Add(txs[i]); err != nil {
return nil, err
}
}
newRoot, err := t.upFromKeys(subRoots)
if err != nil {
return nil, err
}
t.root = newRoot
var invalids []int
for i := 0; i < len(invalidsInBucket); i++ {
invalids = append(invalids, invalidsInBucket[i]...)
}
for i := 0; i < len(dbgStatsPerBucket); i++ {
t.dbg.add(dbgStatsPerBucket[i])
}
return invalids, err
}
// buildTreeFromLeafsSingleThread builds the tree with the given []kv from bottom
// to the root
func (t *Tree) buildTreeFromLeafsSingleThread(l int, kvsRaw []kv) ([]int, error) {
// TODO check that log2(len(leafs)) < t.maxLevels, if not, maxLevels
// would be reached and should return error
if len(kvsRaw) == 0 {
return nil, nil
}
vt := newVT(t.maxLevels, t.hashFunction)
if t.dbg != nil {
vt.params.dbg = newDbgStats()
}
for i := 0; i < len(kvsRaw); i++ {
if err := vt.add(l, kvsRaw[i].k, kvsRaw[i].v); err != nil {
return nil, err
}
}
pairs, err := vt.computeHashes()
if err != nil {
return nil, err
}
// store pairs in db
for i := 0; i < len(pairs); i++ {
if err := t.dbPut(pairs[i][0], pairs[i][1]); err != nil {
return nil, err
}
}
t.dbg.add(vt.params.dbg)
// set tree.root from the virtual tree root
t.root = vt.root.h
return nil, nil // TODO invalids
}
// keys & values must be sorted by path, and the array ks must be length
// multiple of 2
func (t *Tree) upFromKeys(ks [][]byte) ([]byte, error) {
if len(ks) == 1 {
return ks[0], nil
}
var rKs [][]byte
for i := 0; i < len(ks); i += 2 {
if bytes.Equal(ks[i], t.emptyHash) && bytes.Equal(ks[i+1], t.emptyHash) {
// when both sub keys are empty, the key is also empty
rKs = append(rKs, t.emptyHash)
continue
}
k, v, err := newIntermediate(t.hashFunction, ks[i], ks[i+1])
if err != nil {
return nil, err
}
// store k-v to db
if err = t.dbPut(k, v); err != nil {
return nil, err
}
rKs = append(rKs, k)
}
return t.upFromKeys(rKs)
}
func (t *Tree) getLeafs(root []byte) ([][]byte, [][]byte, error) {
var ks, vs [][]byte
err := t.iter(root, func(k, v []byte) {
if v[0] != PrefixValueLeaf {
return
}
leafK, leafV := ReadLeafValue(v)
ks = append(ks, leafK)
vs = append(vs, leafV)
})
return ks, vs, err
}
func (t *Tree) getKeysAtLevel(l int) ([][]byte, error) {
var keys [][]byte
err := t.iterWithStop(t.root, 0, func(currLvl int, k, v []byte) bool {
if currLvl == l && !bytes.Equal(k, t.emptyHash) {
keys = append(keys, k)
}
if currLvl >= l {
return true // to stop the iter from going down
}
return false
})
return keys, err
}
// flp2 computes the floor power of 2, the highest power of 2 under the given
// value.
func flp2(n int) int {
res := 0
for i := n; i >= 1; i-- {
if (i & (i - 1)) == 0 {
res = i
break
}
}
return res
}
// combineInKVSet combines two kv array in one single array without repeated
// keys.
func combineInKVSet(base, toAdd []kv) ([]kv, []int) {
// TODO this is a naive version, this will be implemented in a more
// efficient way or through maps, or through sorted binary search
r := base
var invalids []int
for i := 0; i < len(toAdd); i++ {
e := false
// check if toAdd[i] exists in the base set
for j := 0; j < len(base); j++ {
if bytes.Equal(toAdd[i].k, base[j].k) {
e = true
}
}
if !e {
r = append(r, toAdd[i])
} else {
invalids = append(invalids, toAdd[i].pos)
}
}
return r, invalids
}
// loadVT loads a new virtual tree (vt) from the current Tree, which contains
// the same leafs.
func (t *Tree) loadVT() (vt, error) {
vt := newVT(t.maxLevels, t.hashFunction)
vt.params.dbg = t.dbg
err := t.Iterate(func(k, v []byte) {
switch v[0] {
case PrefixValueEmpty:
case PrefixValueLeaf:
leafK, leafV := ReadLeafValue(v)
if err := vt.add(0, leafK, leafV); err != nil {
panic(err)
}
case PrefixValueIntermediate:
default:
}
})
return vt, err
}
// func computeSimpleAddCost(nLeafs int) int {
// // nLvls 2^nLvls
// nLvls := int(math.Log2(float64(nLeafs)))
// return nLvls * int(math.Pow(2, float64(nLvls)))
// }
//
// func computeFromLeafsAddCost(nLeafs int) int {
// // 2^nLvls * 2 - 1
// nLvls := int(math.Log2(float64(nLeafs)))
// return (int(math.Pow(2, float64(nLvls))) * 2) - 1
// }

+ 43
- 191
addbatch_test.go

@ -6,6 +6,7 @@ import (
"fmt" "fmt"
"math/big" "math/big"
"runtime" "runtime"
"sort"
"testing" "testing"
"time" "time"
@ -31,7 +32,7 @@ func printRes(name string, duration time.Duration) {
func debugTime(descr string, time1, time2 time.Duration) { func debugTime(descr string, time1, time2 time.Duration) {
if debug { if debug {
fmt.Printf("%s was %f times faster than without AddBatch\n",
fmt.Printf("%s was %.02fx times faster than without AddBatch\n",
descr, float64(time1)/float64(time2)) descr, float64(time1)/float64(time2))
} }
} }
@ -151,7 +152,7 @@ func randomBytes(n int) []byte {
return b return b
} }
func TestBuildTreeFromLeafsSingleThread(t *testing.T) {
func TestAddBatchCaseATestVector(t *testing.T) {
c := qt.New(t) c := qt.New(t)
tree1, err := NewTree(memory.NewMemoryStorage(), 100, HashFunctionBlake2b) tree1, err := NewTree(memory.NewMemoryStorage(), 100, HashFunctionBlake2b)
c.Assert(err, qt.IsNil) c.Assert(err, qt.IsNil)
@ -161,6 +162,7 @@ func TestBuildTreeFromLeafsSingleThread(t *testing.T) {
c.Assert(err, qt.IsNil) c.Assert(err, qt.IsNil)
defer tree2.db.Close() defer tree2.db.Close()
// leafs in 2nd level subtrees: [ 6, 0, 1, 1]
testvectorKeys := []string{ testvectorKeys := []string{
"1c7c2265e368314ca58ed2e1f33a326f1220e234a566d55c3605439dbe411642", "1c7c2265e368314ca58ed2e1f33a326f1220e234a566d55c3605439dbe411642",
"2c9f0a578afff5bfa4e0992a43066460faaab9e8e500db0b16647c701cdb16bf", "2c9f0a578afff5bfa4e0992a43066460faaab9e8e500db0b16647c701cdb16bf",
@ -181,43 +183,33 @@ func TestBuildTreeFromLeafsSingleThread(t *testing.T) {
} }
} }
kvs, err := tree2.keysValuesToKvs(keys, values)
c.Assert(err, qt.IsNil)
sortKvs(kvs)
tree2.tx, err = tree2.db.NewTx()
c.Assert(err, qt.IsNil)
// indexes, err := tree2.buildTreeFromLeafsSingleThread(kvs)
indexes, err := tree2.buildTreeFromLeafs(4, kvs)
indexes, err := tree2.AddBatch(keys, values)
c.Assert(err, qt.IsNil) c.Assert(err, qt.IsNil)
// tree1.PrintGraphviz(nil)
// tree2.PrintGraphviz(nil)
c.Check(len(indexes), qt.Equals, 0) c.Check(len(indexes), qt.Equals, 0)
// check that both trees roots are equal // check that both trees roots are equal
c.Check(tree2.Root(), qt.DeepEquals, tree1.Root()) c.Check(tree2.Root(), qt.DeepEquals, tree1.Root())
// 15b6a23945ae6c81342b7eb14e70fff50812dc8791cb15ec791eb08f91784139
}
func TestAddBatchCaseATestVector(t *testing.T) {
c := qt.New(t)
tree1, err := NewTree(memory.NewMemoryStorage(), 100, HashFunctionBlake2b)
// 2nd test vectors
tree1, err = NewTree(memory.NewMemoryStorage(), 100, HashFunctionBlake2b)
c.Assert(err, qt.IsNil) c.Assert(err, qt.IsNil)
defer tree1.db.Close() defer tree1.db.Close()
tree2, err := NewTree(memory.NewMemoryStorage(), 100, HashFunctionBlake2b)
tree2, err = NewTree(memory.NewMemoryStorage(), 100, HashFunctionBlake2b)
c.Assert(err, qt.IsNil) c.Assert(err, qt.IsNil)
defer tree2.db.Close() defer tree2.db.Close()
// leafs in 2nd level subtrees: [ 6, 0, 1, 1]
testvectorKeys := []string{
testvectorKeys = []string{
"1c7c2265e368314ca58ed2e1f33a326f1220e234a566d55c3605439dbe411642", "1c7c2265e368314ca58ed2e1f33a326f1220e234a566d55c3605439dbe411642",
"2c9f0a578afff5bfa4e0992a43066460faaab9e8e500db0b16647c701cdb16bf", "2c9f0a578afff5bfa4e0992a43066460faaab9e8e500db0b16647c701cdb16bf",
"9cb87ec67e875c61390edcd1ab517f443591047709a4d4e45b0f9ed980857b8e",
"9b4e9e92e974a589f426ceeb4cb291dc24893513fecf8e8460992dcf52621d4d",
"1c45cb31f2fa39ec7b9ebf0fad40e0b8296016b5ce8844ae06ff77226379d9a5", "1c45cb31f2fa39ec7b9ebf0fad40e0b8296016b5ce8844ae06ff77226379d9a5",
"d8af98bbbb585129798ae54d5eabbc9d0561d583faf1663b3a3724d15bda4ec7", "d8af98bbbb585129798ae54d5eabbc9d0561d583faf1663b3a3724d15bda4ec7",
"3cd55dbfb8f975f20a0925dfbdabe79fa2d51dd0268afbb8ba6b01de9dfcdd3c",
"5d0a9d6d9f197c091bf054fac9cb60e11ec723d6610ed8578e617b4d46cb43d5",
} }
var keys, values [][]byte
keys = [][]byte{}
values = [][]byte{}
for i := 0; i < len(testvectorKeys); i++ { for i := 0; i < len(testvectorKeys); i++ {
key, err := hex.DecodeString(testvectorKeys[i]) key, err := hex.DecodeString(testvectorKeys[i])
c.Assert(err, qt.IsNil) c.Assert(err, qt.IsNil)
@ -230,69 +222,12 @@ func TestAddBatchCaseATestVector(t *testing.T) {
t.Fatal(err) t.Fatal(err)
} }
} }
// tree1.PrintGraphviz(nil)
indexes, err := tree2.AddBatch(keys, values)
indexes, err = tree2.AddBatch(keys, values)
c.Assert(err, qt.IsNil) c.Assert(err, qt.IsNil)
// tree1.PrintGraphviz(nil)
// tree2.PrintGraphviz(nil)
c.Check(len(indexes), qt.Equals, 0) c.Check(len(indexes), qt.Equals, 0)
// tree1.PrintGraphviz(nil)
// tree2.PrintGraphviz(nil)
// check that both trees roots are equal // check that both trees roots are equal
// fmt.Println(hex.EncodeToString(tree1.Root()))
c.Check(tree2.Root(), qt.DeepEquals, tree1.Root()) c.Check(tree2.Root(), qt.DeepEquals, tree1.Root())
// c.Assert(tree2.Root(), qt.DeepEquals, tree1.Root())
// fmt.Println("\n---2nd test vector---")
//
// // 2nd test vectors
// tree1, err = NewTree(memory.NewMemoryStorage(), 100, HashFunctionBlake2b)
// c.Assert(err, qt.IsNil)
// defer tree1.db.Close()
//
// tree2, err = NewTree(memory.NewMemoryStorage(), 100, HashFunctionBlake2b)
// c.Assert(err, qt.IsNil)
// defer tree2.db.Close()
//
// testvectorKeys = []string{
// "1c7c2265e368314ca58ed2e1f33a326f1220e234a566d55c3605439dbe411642",
// "2c9f0a578afff5bfa4e0992a43066460faaab9e8e500db0b16647c701cdb16bf",
// "9cb87ec67e875c61390edcd1ab517f443591047709a4d4e45b0f9ed980857b8e",
// "9b4e9e92e974a589f426ceeb4cb291dc24893513fecf8e8460992dcf52621d4d",
// "1c45cb31f2fa39ec7b9ebf0fad40e0b8296016b5ce8844ae06ff77226379d9a5",
// "d8af98bbbb585129798ae54d5eabbc9d0561d583faf1663b3a3724d15bda4ec7",
// "3cd55dbfb8f975f20a0925dfbdabe79fa2d51dd0268afbb8ba6b01de9dfcdd3c",
// "5d0a9d6d9f197c091bf054fac9cb60e11ec723d6610ed8578e617b4d46cb43d5",
// }
// keys = [][]byte{}
// values = [][]byte{}
// for i := 0; i < len(testvectorKeys); i++ {
// key, err := hex.DecodeString(testvectorKeys[i])
// c.Assert(err, qt.IsNil)
// keys = append(keys, key)
// values = append(values, []byte{0})
// }
//
// for i := 0; i < len(keys); i++ {
// if err := tree1.Add(keys[i], values[i]); err != nil {
// t.Fatal(err)
// }
// }
//
// indexes, err = tree2.AddBatch(keys, values)
// c.Assert(err, qt.IsNil)
// // tree1.PrintGraphviz(nil)
// // tree2.PrintGraphviz(nil)
//
// c.Check(len(indexes), qt.Equals, 0)
//
// // check that both trees roots are equal
// // fmt.Println(hex.EncodeToString(tree1.Root()))
// c.Check(tree2.Root(), qt.DeepEquals, tree1.Root())
} }
func TestAddBatchCaseARandomKeys(t *testing.T) { func TestAddBatchCaseARandomKeys(t *testing.T) {
@ -417,83 +352,6 @@ func TestAddBatchCaseBRepeatedLeafs(t *testing.T) {
c.Check(tree2.Root(), qt.DeepEquals, tree1.Root()) c.Check(tree2.Root(), qt.DeepEquals, tree1.Root())
} }
func TestCombineInKVSet(t *testing.T) {
c := qt.New(t)
var a, b, expected []kv
for i := 0; i < 10; i++ {
k := BigIntToBytes(big.NewInt(int64(i)))
kv := kv{k: k}
if i < 7 {
a = append(a, kv)
}
if i >= 4 {
b = append(b, kv)
}
expected = append(expected, kv)
}
r, invalids := combineInKVSet(a, b)
for i := 0; i < len(r); i++ {
c.Assert(r[i].k, qt.DeepEquals, expected[i].k)
}
c.Assert(len(invalids), qt.Equals, 7-4)
}
func TestGetKeysAtLevel(t *testing.T) {
c := qt.New(t)
tree, err := NewTree(memory.NewMemoryStorage(), 100, HashFunctionPoseidon)
c.Assert(err, qt.IsNil)
defer tree.db.Close()
for i := 0; i < 32; i++ {
k := BigIntToBytes(big.NewInt(int64(i)))
v := BigIntToBytes(big.NewInt(int64(i * 2)))
if err := tree.Add(k, v); err != nil {
t.Fatal(err)
}
}
keys, err := tree.getKeysAtLevel(2)
c.Assert(err, qt.IsNil)
expected := []string{
"a5d5f14fce7348e40751496cf25d107d91b0bd043435b9577d778a01f8aa6111",
"e9e8dd9b28a7f81d1ff34cb5cefc0146dd848b31031a427b79bdadb62e7f6910",
}
for i := 0; i < len(keys); i++ {
c.Assert(hex.EncodeToString(keys[i]), qt.Equals, expected[i])
}
keys, err = tree.getKeysAtLevel(3)
c.Assert(err, qt.IsNil)
expected = []string{
"9f12c13e52bca96ad4882a26558e48ab67ddd63e062b839207e893d961390f01",
"16d246dd6826ec7346c7328f11c4261facf82d4689f33263ff6e207956a77f21",
"4a22cc901c6337daa17a431fa20170684b710e5f551509511492ec24e81a8f2f",
"470d61abcbd154977bffc9a9ec5a8daff0caabcf2a25e8441f604c79daa0f82d",
}
for i := 0; i < len(keys); i++ {
c.Assert(hex.EncodeToString(keys[i]), qt.Equals, expected[i])
}
keys, err = tree.getKeysAtLevel(4)
c.Assert(err, qt.IsNil)
expected = []string{
"7a5d1c81f7b96318012de3417e53d4f13df5b1337718651cd29d0cb0a66edd20",
"3408213e4e844bdf3355eb8781c74e31626812898c2dbe141ed6d2c92256fc1c",
"dfd8a4d0b6954a3e9f3892e655b58d456eeedf9367f27dfdd9bc2dd6a5577312",
"9e99fbec06fb2a6725997c12c4995f62725eb4cce4808523a5a5e80cca64b007",
"0befa1e070231dbf4e8ff841c05878cdec823e0c09594c24910a248b3ff5a628",
"b7131b0a15c772a57005a4dc5d0d6dd4b3414f5d9ee7408ce5e86c5ab3520e04",
"6d1abe0364077846a56bab1deb1a04883eb796b74fe531a7676a9a370f83ab21",
"4270116394bede69cf9cd72069eca018238080380bef5de75be8dcbbe968e105",
}
for i := 0; i < len(keys); i++ {
c.Assert(hex.EncodeToString(keys[i]), qt.Equals, expected[i])
}
}
func TestSplitInBuckets(t *testing.T) { func TestSplitInBuckets(t *testing.T) {
c := qt.New(t) c := qt.New(t)
@ -563,11 +421,37 @@ func TestSplitInBuckets(t *testing.T) {
sortKvs(buckets[i]) sortKvs(buckets[i])
c.Assert(len(buckets[i]), qt.Equals, len(expected[i])) c.Assert(len(buckets[i]), qt.Equals, len(expected[i]))
for j := 0; j < len(buckets[i]); j++ { for j := 0; j < len(buckets[i]); j++ {
c.Check(hex.EncodeToString(buckets[i][j].k[:4]), qt.Equals, expected[i][j])
c.Check(hex.EncodeToString(buckets[i][j].k[:4]),
qt.Equals, expected[i][j])
} }
} }
} }
// compareBytes compares byte slices where the bytes are compared from left to
// right and each byte is compared by bit from right to left
func compareBytes(a, b []byte) bool {
// WIP
for i := 0; i < len(a); i++ {
for j := 0; j < 8; j++ {
aBit := a[i] & (1 << j)
bBit := b[i] & (1 << j)
if aBit > bBit {
return false
} else if aBit < bBit {
return true
}
}
}
return false
}
// sortKvs sorts the kv by path
func sortKvs(kvs []kv) {
sort.Slice(kvs, func(i, j int) bool {
return compareBytes(kvs[i].keyPath, kvs[j].keyPath)
})
}
func TestAddBatchCaseC(t *testing.T) { func TestAddBatchCaseC(t *testing.T) {
c := qt.New(t) c := qt.New(t)
@ -878,37 +762,5 @@ func TestLoadVT(t *testing.T) {
c.Check(tree.Root(), qt.DeepEquals, vt.root.h) c.Check(tree.Root(), qt.DeepEquals, vt.root.h)
} }
// func printLeafs(name string, t *Tree) {
// w := bytes.NewBufferString("")
//
// err := t.Iterate(func(k, v []byte) {
// if v[0] != PrefixValueLeaf {
// return
// }
// leafK, _ := readLeafValue(v)
// fmt.Fprintf(w, hex.EncodeToString(leafK[:4])+"\n")
// })
// if err != nil {
// panic(err)
// }
// err = ioutil.WriteFile(name, w.Bytes(), 0644)
// if err != nil {
// panic(err)
// }
//
// }
// func TestComputeCosts(t *testing.T) {
// fmt.Println(computeSimpleAddCost(10))
// fmt.Println(computeFromLeafsAddCost(10))
//
// fmt.Println(computeSimpleAddCost(1024))
// fmt.Println(computeFromLeafsAddCost(1024))
// }
// TODO test tree with nLeafs > minLeafsThreshold, but that at level L, there is
// less keys than nBuckets (so CASE C could be applied if first few leafs are
// added to balance the tree)
// TODO test adding batch with repeated keys in the batch // TODO test adding batch with repeated keys in the batch
// TODO test adding batch with multiple invalid keys // TODO test adding batch with multiple invalid keys

+ 71
- 0
tree.go

@ -116,6 +116,77 @@ func (t *Tree) HashFunction() HashFunction {
return t.hashFunction return t.hashFunction
} }
// AddBatch adds a batch of key-values to the Tree. Returns an array containing
// the indexes of the keys failed to add.
func (t *Tree) AddBatch(keys, values [][]byte) ([]int, error) {
t.updateAccessTime()
t.Lock()
defer t.Unlock()
vt, err := t.loadVT()
if err != nil {
return nil, err
}
// TODO check that keys & values is valid for Tree.hashFunction
invalids, err := vt.addBatch(keys, values)
if err != nil {
return nil, err
}
// once the VirtualTree is build, compute the hashes
pairs, err := vt.computeHashes()
if err != nil {
return nil, err
}
t.root = vt.root.h
// store pairs in db
t.tx, err = t.db.NewTx()
if err != nil {
return nil, err
}
for i := 0; i < len(pairs); i++ {
if err := t.dbPut(pairs[i][0], pairs[i][1]); err != nil {
return nil, err
}
}
// store root to db
if err := t.dbPut(dbKeyRoot, t.root); err != nil {
return nil, err
}
// update nLeafs
if err := t.incNLeafs(len(keys) - len(invalids)); err != nil {
return nil, err
}
// commit db tx
if err := t.tx.Commit(); err != nil {
return nil, err
}
return invalids, nil
}
// loadVT loads a new virtual tree (vt) from the current Tree, which contains
// the same leafs.
func (t *Tree) loadVT() (vt, error) {
vt := newVT(t.maxLevels, t.hashFunction)
vt.params.dbg = t.dbg
err := t.Iterate(func(k, v []byte) {
if v[0] != PrefixValueLeaf {
return
}
leafK, leafV := ReadLeafValue(v)
if err := vt.add(0, leafK, leafV); err != nil {
panic(err)
}
})
return vt, err
}
// Add inserts the key-value into the Tree. If the inputs come from a *big.Int, // Add inserts the key-value into the Tree. If the inputs come from a *big.Int,
// is expected that are represented by a Little-Endian byte array (for circom // is expected that are represented by a Little-Endian byte array (for circom
// compatibility). // compatibility).

+ 96
- 63
vt.go

@ -30,6 +30,13 @@ type params struct {
dbg *dbgStats dbg *dbgStats
} }
type kv struct {
pos int // original position in the inputted array
keyPath []byte
k []byte
v []byte
}
func (p *params) keysValuesToKvs(ks, vs [][]byte) ([]kv, error) { func (p *params) keysValuesToKvs(ks, vs [][]byte) ([]kv, error) {
if len(ks) != len(vs) { if len(ks) != len(vs) {
return nil, fmt.Errorf("len(keys)!=len(values) (%d!=%d)", return nil, fmt.Errorf("len(keys)!=len(values) (%d!=%d)",
@ -68,8 +75,12 @@ func newVT(maxLevels int, hash HashFunction) vt {
} }
} }
// addBatch adds a batch of key-values to the VirtualTree. Returns an array
// containing the indexes of the keys failed to add. Does not include the
// computation of hashes of the nodes neither the storage of the key-values of
// the tree into the db. After addBatch, vt.computeHashes should be called to
// compute the hashes of all the nodes of the tree.
func (t *vt) addBatch(ks, vs [][]byte) ([]int, error) { func (t *vt) addBatch(ks, vs [][]byte) ([]int, error) {
// parallelize adding leafs in the virtual tree
nCPU := flp2(runtime.NumCPU()) nCPU := flp2(runtime.NumCPU())
if nCPU == 1 || len(ks) < nCPU { if nCPU == 1 || len(ks) < nCPU {
var invalids []int var invalids []int
@ -95,7 +106,37 @@ func (t *vt) addBatch(ks, vs [][]byte) ([]int, error) {
return nil, err return nil, err
} }
if len(nodesAtL) != nCPU && t.root != nil { if len(nodesAtL) != nCPU && t.root != nil {
// CASE E: add one key at each bucket, and then do CASE D
/*
Already populated Tree but Unbalanced
- Need to fill M1 and M2, and then will be able to continue with the flow
- Search for M1 & M2 in the inputed Keys
- Add M1 & M2 to the Tree
- From here can continue with the flow
R
/ \
/ \
/ \
* *
| \
| \
| \
L: M1 * M2 * (where M1 and M2 are empty)
/ | /
/ | /
/ | /
A * *
/ \ | \
/ \ | \
/ \ | \
B * * C
/ \ |\
... ... | \
| \
D E
*/
// add one key at each bucket, and then continue with the flow
for i := 0; i < len(buckets); i++ { for i := 0; i < len(buckets); i++ {
// add one leaf of the bucket, if there is an error when // add one leaf of the bucket, if there is an error when
// adding the k-v, try to add the next one of the bucket // adding the k-v, try to add the next one of the bucket
@ -120,8 +161,7 @@ func (t *vt) addBatch(ks, vs [][]byte) ([]int, error) {
} }
} }
if len(nodesAtL) != nCPU { if len(nodesAtL) != nCPU {
fmt.Println("ASDF")
panic("should not happen")
panic("should not happen") // TODO TMP
} }
subRoots := make([]*node, nCPU) subRoots := make([]*node, nCPU)
@ -131,8 +171,6 @@ func (t *vt) addBatch(ks, vs [][]byte) ([]int, error) {
wg.Add(nCPU) wg.Add(nCPU)
for i := 0; i < nCPU; i++ { for i := 0; i < nCPU; i++ {
go func(cpu int) { go func(cpu int) {
sortKvs(buckets[cpu])
bucketVT := newVT(t.params.maxLevels-l, t.params.hashFunction) bucketVT := newVT(t.params.maxLevels-l, t.params.hashFunction)
bucketVT.root = nodesAtL[cpu] bucketVT.root = nodesAtL[cpu]
for j := 0; j < len(buckets[cpu]); j++ { for j := 0; j < len(buckets[cpu]); j++ {
@ -214,8 +252,8 @@ func upFromNodes(ns []*node) (*node, error) {
var res []*node var res []*node
for i := 0; i < len(ns); i += 2 { for i := 0; i < len(ns); i += 2 {
// if ns[i].typ() == vtEmpty && ns[i+1].typ() == vtEmpty {
if ns[i] == nil && ns[i+1] == nil {
if ns[i].typ() == vtEmpty && ns[i+1].typ() == vtEmpty {
// if ns[i] == nil && ns[i+1] == nil {
// when both sub nodes are empty, the node is also empty // when both sub nodes are empty, the node is also empty
res = append(res, ns[i]) // empty node res = append(res, ns[i]) // empty node
continue continue
@ -229,56 +267,6 @@ func upFromNodes(ns []*node) (*node, error) {
return upFromNodes(res) return upFromNodes(res)
} }
// func upFromNodesComputingHashes(p *params, ns []*node, pairs [][2][]byte) (
// [][2][]byte, *node, error) {
// if len(ns) == 1 {
// return pairs, ns[0], nil
// }
//
// var res []*node
// for i := 0; i < len(ns); i += 2 {
// if ns[i] == nil && ns[i+1] == nil {
// // when both sub nodes are empty, the node is also empty
// res = append(res, ns[i]) // empty node
// continue
// }
// n := &node{
// l: ns[i],
// r: ns[i+1],
// }
//
// if n.l == nil {
// n.l = &node{
// h: p.emptyHash,
// }
// }
// if n.r == nil {
// n.r = &node{
// h: p.emptyHash,
// }
// }
// if n.l.typ() == vtEmpty && n.r.typ() == vtLeaf {
// n = n.r
// }
// if n.r.typ() == vtEmpty && n.l.typ() == vtLeaf {
// n = n.l
// }
//
// // once the sub nodes are computed, can compute the current node
// // hash
// p.dbg.incHash()
// k, v, err := newIntermediate(p.hashFunction, n.l.h, n.r.h)
// if err != nil {
// return nil, nil, err
// }
// n.h = k
// kv := [2][]byte{k, v}
// pairs = append(pairs, kv)
// res = append(res, n)
// }
// return upFromNodesComputingHashes(p, res, pairs)
// }
func (t *vt) add(fromLvl int, k, v []byte) error { func (t *vt) add(fromLvl int, k, v []byte) error {
leaf := newLeafNode(t.params, k, v) leaf := newLeafNode(t.params, k, v)
if t.root == nil { if t.root == nil {
@ -320,8 +308,7 @@ func (t *vt) computeHashes() ([][2][]byte, error) {
t.params.maxLevels, bucketVT.params, bucketPairs[cpu]) t.params.maxLevels, bucketVT.params, bucketPairs[cpu])
if err != nil { if err != nil {
// TODO WIP // TODO WIP
fmt.Println("TODO ERR, err:", err)
panic(err)
panic("TODO" + err.Error())
} }
subRoots[cpu] = bucketVT.root subRoots[cpu] = bucketVT.root
@ -444,7 +431,7 @@ func (n *node) add(p *params, currLvl int, leaf *node) error {
case vtEmpty: case vtEmpty:
panic(fmt.Errorf("EMPTY %v", n)) // TODO TMP panic(fmt.Errorf("EMPTY %v", n)) // TODO TMP
default: default:
return fmt.Errorf("ERR")
return fmt.Errorf("ERR") // TODO TMP
} }
return nil return nil
@ -484,6 +471,53 @@ func (n *node) downUntilDivergence(p *params, currLvl int, oldLeaf, newLeaf *nod
return nil return nil
} }
func splitInBuckets(kvs []kv, nBuckets int) [][]kv {
buckets := make([][]kv, nBuckets)
// 1. classify the keyvalues into buckets
for i := 0; i < len(kvs); i++ {
pair := kvs[i]
// bucketnum := keyToBucket(pair.k, nBuckets)
bucketnum := keyToBucket(pair.keyPath, nBuckets)
buckets[bucketnum] = append(buckets[bucketnum], pair)
}
return buckets
}
// TODO rename in a more 'real' name (calculate bucket from/for key)
func keyToBucket(k []byte, nBuckets int) int {
nLevels := int(math.Log2(float64(nBuckets)))
b := make([]int, nBuckets)
for i := 0; i < nBuckets; i++ {
b[i] = i
}
r := b
mid := len(r) / 2 //nolint:gomnd
for i := 0; i < nLevels; i++ {
if int(k[i/8]&(1<<(i%8))) != 0 {
r = r[mid:]
mid = len(r) / 2 //nolint:gomnd
} else {
r = r[:mid]
mid = len(r) / 2 //nolint:gomnd
}
}
return r[0]
}
// flp2 computes the floor power of 2, the highest power of 2 under the given
// value.
func flp2(n int) int {
res := 0
for i := n; i >= 1; i-- {
if (i & (i - 1)) == 0 {
res = i
break
}
}
return res
}
// returns an array of key-values to store in the db // returns an array of key-values to store in the db
func (n *node) computeHashes(currLvl, maxLvl int, p *params, pairs [][2][]byte) ( func (n *node) computeHashes(currLvl, maxLvl int, p *params, pairs [][2][]byte) (
[][2][]byte, error) { [][2][]byte, error) {
@ -539,8 +573,7 @@ func (n *node) computeHashes(currLvl, maxLvl int, p *params, pairs [][2][]byte)
pairs = append(pairs, kv) pairs = append(pairs, kv)
case vtEmpty: case vtEmpty:
default: default:
fmt.Println("n.computeHashes type no match", t)
return nil, fmt.Errorf("ERR TMP") // TODO
return nil, fmt.Errorf("ERR:n.computeHashes type (%d) no match", t) // TODO TMP
} }
return pairs, nil return pairs, nil

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