added stddev stat

internal/reporter.go

@@ -49,6 +49,7 @@ func (trw *TextReportWriter) Write(ts pkg.TracerSummary, config *BenchmarkSpec)
 		trw.writeStatNano2Sec("mean", stats.Mean)
 		trw.writeStatNano2Sec("median", stats.Median)
 		trw.writeStatNano2Sec("p90", func() (float64, error) { return stats.Percentile(90) })
+		trw.writeStatNano2Sec("stddev", stats.StdDev)
 		trw.writeErrorRateStat("errors", stats.ErrorRate)
 		trw.writeNewLine()
 		trw.writer.Flush()
@@ -80,6 +81,16 @@ func (trw *TextReportWriter) writeStatNano2Sec(name string, f func() (float64, e
 	}
 }
 
+func (trw *TextReportWriter) writeNumericStat(name string, f func() (float64, error)) {
+	value, err := f()
+	if err == nil {
+		trw.writeStatTitle(name)
+		trw.writer.WriteString(fmt.Sprintf("%.3f\r\n", value))
+	} else {
+		trw.writeStatError(name)
+	}
+}
+
 func (trw *TextReportWriter) writeErrorRateStat(name string, f func() float64) {
 	trw.writeStatTitle(name)
 

internal/spec.go

@@ -3,10 +3,10 @@ package internal
 import (
 	"encoding/json"
 	"fmt"
+	log "github.com/sirupsen/logrus"
 	"io/ioutil"
 	"os"
 	"strings"
-	log "github.com/sirupsen/logrus"
 
 	"github.com/go-playground/locales/en"
 	ut "github.com/go-playground/universal-translator"

pkg/summary.go

@@ -11,6 +11,7 @@ type Stats interface {
 	Mean() (float64, error)
 	Median() (float64, error)
 	Percentile(percent float64) (float64, error)
+	StdDev() (float64, error)
 	ErrorRate() float64
 }
 
@@ -63,6 +64,10 @@ func (ss *sstats) Mean() (float64, error) {
 	return stats.Mean(ss.float64Samples)
 }
 
+func (ss *sstats) StdDev() (float64, error) {
+	return stats.StandardDeviation(ss.float64Samples)
+}
+
 func (ss *sstats) Median() (float64, error) {
 	return stats.Median(ss.float64Samples)
 }