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