mirror of
https://source.quilibrium.com/quilibrium/ceremonyclient.git
synced 2024-12-28 01:25:18 +00:00
78 lines
2.0 KiB
Go
78 lines
2.0 KiB
Go
// Copyright 2018 The Cockroach Authors.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
|
|
// implied. See the License for the specific language governing
|
|
// permissions and limitations under the License. See the AUTHORS file
|
|
// for names of contributors.
|
|
|
|
package randvar
|
|
|
|
import (
|
|
"sync"
|
|
|
|
"golang.org/x/exp/rand"
|
|
)
|
|
|
|
// SkewedLatest is a random number generator that generates numbers in
|
|
// the range [min, max], but skews it towards max using a zipfian
|
|
// distribution.
|
|
type SkewedLatest struct {
|
|
mu struct {
|
|
sync.RWMutex
|
|
max uint64
|
|
zipf *Zipf
|
|
}
|
|
}
|
|
|
|
// NewDefaultSkewedLatest constructs a new SkewedLatest generator with the
|
|
// default parameters.
|
|
func NewDefaultSkewedLatest() (*SkewedLatest, error) {
|
|
return NewSkewedLatest(1, defaultMax, defaultTheta)
|
|
}
|
|
|
|
// NewSkewedLatest constructs a new SkewedLatest generator with the given
|
|
// parameters. It returns an error if the parameters are outside the accepted
|
|
// range.
|
|
func NewSkewedLatest(min, max uint64, theta float64) (*SkewedLatest, error) {
|
|
z := &SkewedLatest{}
|
|
z.mu.max = max
|
|
zipf, err := NewZipf(0, max-min, theta)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
z.mu.zipf = zipf
|
|
return z, nil
|
|
}
|
|
|
|
// IncMax increments max.
|
|
func (z *SkewedLatest) IncMax(delta int) {
|
|
z.mu.Lock()
|
|
z.mu.zipf.IncMax(delta)
|
|
z.mu.max += uint64(delta)
|
|
z.mu.Unlock()
|
|
}
|
|
|
|
// Max returns max.
|
|
func (z *SkewedLatest) Max() uint64 {
|
|
z.mu.Lock()
|
|
defer z.mu.Unlock()
|
|
return z.mu.zipf.Max()
|
|
}
|
|
|
|
// Uint64 returns a random Uint64 between min and max, where keys near max are
|
|
// most likely to be drawn.
|
|
func (z *SkewedLatest) Uint64(rng *rand.Rand) uint64 {
|
|
z.mu.RLock()
|
|
result := z.mu.max - z.mu.zipf.Uint64(rng)
|
|
z.mu.RUnlock()
|
|
return result
|
|
}
|