forked from jaegertracing/jaeger
/
weightvectorcache.go
58 lines (52 loc) · 1.59 KB
/
weightvectorcache.go
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// Copyright (c) 2018 The Jaeger 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.
package adaptive
import (
"math"
"sync"
)
// WeightVectorCache stores normalizing weight vectors of different lengths.
// The head of each weight vector contains the largest weight.
type WeightVectorCache struct {
sync.Mutex
cache map[int][]float64
}
// NewWeightVectorCache returns a new weights vector cache.
func NewWeightVectorCache() *WeightVectorCache {
// TODO allow users to plugin different weighting algorithms
return &WeightVectorCache{
cache: make(map[int][]float64),
}
}
// GetWeights returns weights for the specified length { w(i) = i ^ 4, i=1..L }, normalized.
func (c *WeightVectorCache) GetWeights(length int) []float64 {
c.Lock()
defer c.Unlock()
if weights, ok := c.cache[length]; ok {
return weights
}
weights := make([]float64, 0, length)
var sum float64
for i := length; i > 0; i-- {
w := math.Pow(float64(i), 4)
weights = append(weights, w)
sum += w
}
// normalize
for i := 0; i < length; i++ {
weights[i] = weights[i] / sum
}
c.cache[length] = weights
return weights
}