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128 lines
2.1 KiB
128 lines
2.1 KiB
package simd
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import (
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"fmt"
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"runtime"
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"sort"
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"sync"
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)
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// Search finds the key using the naive way
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func Naive(xs []uint64, k uint64) int16 {
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var i int
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for i = 0; i < len(xs); i += 2 {
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x := xs[i]
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if x >= k {
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return int16(i / 2)
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}
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}
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return int16(i / 2)
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}
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func Clever(xs []uint64, k uint64) int16 {
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if len(xs) < 8 {
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return Naive(xs, k)
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}
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var twos, pk [4]uint64
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pk[0] = k
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pk[1] = k
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pk[2] = k
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pk[3] = k
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for i := 0; i < len(xs); i += 8 {
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twos[0] = xs[i]
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twos[1] = xs[i+2]
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twos[2] = xs[i+4]
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twos[3] = xs[i+6]
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if twos[0] >= pk[0] {
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return int16(i / 2)
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}
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if twos[1] >= pk[1] {
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return int16((i + 2) / 2)
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}
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if twos[2] >= pk[2] {
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return int16((i + 4) / 2)
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}
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if twos[3] >= pk[3] {
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return int16((i + 6) / 2)
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}
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}
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return int16(len(xs) / 2)
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}
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func Parallel(xs []uint64, k uint64) int16 {
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cpus := runtime.NumCPU()
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if cpus%2 != 0 {
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panic(fmt.Sprintf("odd number of CPUs %v", cpus))
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}
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sz := len(xs)/cpus + 1
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var wg sync.WaitGroup
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retChan := make(chan int16, cpus)
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for i := 0; i < len(xs); i += sz {
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end := i + sz
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if end >= len(xs) {
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end = len(xs)
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}
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chunk := xs[i:end]
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wg.Add(1)
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go func(hd int16, xs []uint64, k uint64, wg *sync.WaitGroup, ch chan int16) {
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for i := 0; i < len(xs); i += 2 {
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if xs[i] >= k {
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ch <- (int16(i) + hd) / 2
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break
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}
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}
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wg.Done()
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}(int16(i), chunk, k, &wg, retChan)
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}
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wg.Wait()
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close(retChan)
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var min int16 = (1 << 15) - 1
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for i := range retChan {
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if i < min {
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min = i
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}
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}
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if min == (1<<15)-1 {
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return int16(len(xs) / 2)
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}
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return min
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}
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func Binary(keys []uint64, key uint64) int16 {
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return int16(sort.Search(len(keys), func(i int) bool {
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if i*2 >= len(keys) {
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return true
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}
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return keys[i*2] >= key
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}))
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}
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func cmp2_native(twos, pk [2]uint64) int16 {
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if twos[0] == pk[0] {
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return 0
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}
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if twos[1] == pk[1] {
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return 1
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}
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return 2
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}
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func cmp4_native(fours, pk [4]uint64) int16 {
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for i := range fours {
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if fours[i] >= pk[i] {
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return int16(i)
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}
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}
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return 4
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}
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func cmp8_native(a [8]uint64, pk [4]uint64) int16 {
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for i := range a {
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if a[i] >= pk[0] {
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return int16(i)
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}
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}
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return 8
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}
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