github.com/m3db/m3@v1.5.0/src/aggregator/aggregation/common.go (about)

     1  // Copyright (c) 2017 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
     6  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package aggregation
    22  
    23  import (
    24  	"math"
    25  
    26  	"github.com/m3db/m3/src/metrics/aggregation"
    27  )
    28  
    29  func stdev(count int64, sumSq, sum float64) float64 {
    30  	div := count * (count - 1)
    31  	if div == 0 {
    32  		return 0.0
    33  	}
    34  	num := float64(count)*sumSq - sum*sum
    35  	return math.Sqrt(num / float64(div))
    36  }
    37  
    38  func isExpensive(aggTypes aggregation.Types) bool {
    39  	for _, aggType := range aggTypes {
    40  		if aggType == aggregation.SumSq || aggType == aggregation.Stdev {
    41  			return true
    42  		}
    43  	}
    44  	return false
    45  }
    46  
    47  // MaybeReplaceAnnotation replaces the current annotation with the new annotation, returning the updated ref for
    48  // current annotation.
    49  func MaybeReplaceAnnotation(currentAnnotation, newAnnotation []byte) []byte {
    50  	if len(newAnnotation) == 0 {
    51  		return currentAnnotation
    52  	}
    53  	// Keep the last annotation which was set. Reuse any previous allocation while taking a copy.
    54  	result := currentAnnotation[:0]
    55  	if cap(result) < len(newAnnotation) {
    56  		// Twice as long in case another one comes in
    57  		// and we could avoid realloc as long as less than this first alloc.
    58  		result = make([]byte, 0, 2*len(newAnnotation))
    59  	}
    60  	return append(result, newAnnotation...)
    61  }