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pert.go
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pert.go
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package graphman
import (
"fmt"
"math"
"strconv"
"strings"
"time"
)
const (
Day = 24 * time.Hour
Week = 7 * Day
)
type PertAttrs struct {
Pessimistic, Realistic, Optimistic float64
IsZeroTimeActivity bool // a.k.a DummyActivity
IsUntitled bool
IsAction, IsState bool
IsNonStandardGraph bool
IsStart, IsFinish bool
IsUndefinedDependency bool
}
func (pa PertAttrs) WeightedEstimate() float64 {
return (pa.Pessimistic + pa.Optimistic + 4*pa.Realistic) / 6
}
func (pa PertAttrs) StandardDeviation() float64 {
return (pa.Pessimistic - pa.Optimistic) / 6
}
func (pa PertAttrs) Variance() float64 {
sd := pa.StandardDeviation()
return sd * sd
}
func (pa PertAttrs) AverageEstimate() float64 {
return (pa.Pessimistic + pa.Optimistic + pa.Realistic) / 3
}
func (pa PertAttrs) String() string {
if pa.Optimistic == 0 || pa.Realistic == 0 || pa.Pessimistic == 0 {
return ""
}
return fmt.Sprintf(
"To=%s,Tm=%s,Tp=%s,Te=%s,σe=%s,Ve=%s",
prettyFloat(pa.Optimistic),
prettyFloat(pa.Realistic),
prettyFloat(pa.Pessimistic),
prettyFloat(pa.WeightedEstimate()),
prettyFloat(pa.StandardDeviation()),
prettyFloat(pa.Variance()),
)
}
func prettyFloat(f float64) string {
out := strconv.FormatFloat(f, 'f', 2, 64)
out = strings.TrimRight(out, "0")
out = strings.TrimRight(out, ".")
return out
}
type PertResult struct {
CriticalPathVariance float64
CriticalPathStandardDeviation float64
CriticalPath Path
}
func (pr PertResult) String() string {
return fmt.Sprintf(
"Tσe=%s,TVe=%s",
prettyFloat(pr.CriticalPathStandardDeviation),
prettyFloat(pr.CriticalPathVariance),
)
}
func ComputePert(g *Graph) PertResult {
result := PertResult{}
// apply pert defaults before computing
for _, edge := range g.edges {
pa := edge.GetPert()
if pa == nil {
if edge.Attrs == nil {
edge.Attrs = make(map[string]interface{})
}
edge.SetPertEstimates(1, 1, 1)
pa = edge.GetPert()
}
if pa.Realistic == 0 {
pa.Realistic = 1
}
if pa.Pessimistic == 0 && pa.Optimistic == 0 {
pa.Pessimistic = pa.Realistic
pa.Optimistic = pa.Realistic
}
result.CriticalPathVariance += pa.Variance()
}
result.CriticalPathStandardDeviation = math.Sqrt(result.CriticalPathVariance)
return result
}