feat: pert calculation

attr.go

@@ -40,10 +40,18 @@ func (a Attrs) SetTitle(title string) Attrs {
 }
 
 func (a Attrs) SetPert(opt, real, pess float64) Attrs {
-	a["pert"] = PertAttrs{
+	a["pert"] = &PertAttrs{
 		Optimistic:  opt,
 		Realistic:   real,
 		Pessimistic: pess,
 	}
 	return a
 }
+
+func (a Attrs) GetPert() *PertAttrs {
+	pa, found := a["pert"]
+	if !found {
+		return nil
+	}
+	return pa.(*PertAttrs)
+}

edge.go

@@ -17,6 +17,8 @@ func newEdge(src, dst *Vertex, attrs ...Attrs) *Edge {
 	var a Attrs
 	if len(attrs) > 0 {
 		a = attrs[0]
+	} else {
+		a = make(map[string]interface{})
 	}
 	return &Edge{
 		src:   src,

pert.go

@@ -2,6 +2,7 @@ package graphman
 
 import (
 	"fmt"
+	"math"
 	"strconv"
 	"strings"
 	"time"
@@ -47,3 +48,42 @@ func prettyFloat(f float64) string {
 	out = strings.TrimRight(out, ".")
 	return out
 }
+
+type PertResult struct {
+	CriticalPathVariance          float64
+	CriticalPathStandardDeviation float64
+}
+
+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.SetPert(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
+}

pert_test.go

@@ -4,28 +4,58 @@ import (
 	"fmt"
 )
 
-func Example_pert() {
+func ExamplePertResult_withValue() {
 	graph := New()
-	graph.AddEdge("1", "2", Attrs{}.SetTitle("a").SetPert(3, 6, 15))
-	graph.AddEdge("1", "3", Attrs{}.SetTitle("b").SetPert(2, 5, 14))
-	graph.AddEdge("1", "4", Attrs{}.SetTitle("c").SetPert(6, 12, 30))
-	graph.AddEdge("2", "5", Attrs{}.SetTitle("d").SetPert(2, 5, 8))
-	graph.AddEdge("2", "6", Attrs{}.SetTitle("e").SetPert(5, 11, 17))
-	graph.AddEdge("3", "6", Attrs{}.SetTitle("f").SetPert(3, 6, 15))
-	graph.AddEdge("4", "7", Attrs{}.SetTitle("g").SetPert(3, 9, 27))
-	graph.AddEdge("5", "7", Attrs{}.SetTitle("h").SetPert(1, 4, 7))
-	graph.AddEdge("6", "7", Attrs{}.SetTitle("i").SetPert(4, 19, 28))
+	graph.AddEdge("1", "2", Attrs{}.SetPert(3, 6, 15))
+	graph.AddEdge("1", "3", Attrs{}.SetPert(2, 5, 14))
+	graph.AddEdge("1", "4", Attrs{}.SetPert(6, 12, 30))
+	graph.AddEdge("2", "5", Attrs{}.SetPert(2, 5, 8))
+	graph.AddEdge("2", "6", Attrs{}.SetPert(5, 11, 17))
+	graph.AddEdge("3", "6", Attrs{}.SetPert(3, 6, 15))
+	graph.AddEdge("4", "7", Attrs{}.SetPert(3, 9, 27))
+	graph.AddEdge("5", "7", Attrs{}.SetPert(1, 4, 7))
+	graph.AddEdge("6", "7", Attrs{}.SetPert(4, 19, 28))
+
+	fmt.Println("graph before computing:")
+	for _, e := range graph.Edges() {
+		fmt.Println("*", e)
+	}
+	fmt.Println()
+
+	result := ComputePert(graph)
+	fmt.Println("graph after computing:")
 	for _, e := range graph.Edges() {
 		fmt.Println("*", e)
 	}
+	fmt.Println("result:", result)
+
+	// Output:
+}
+
+func ExamplePertResult_withoutValue() {
+	graph := New()
+	graph.AddEdge("1", "2")
+	graph.AddEdge("1", "3")
+	graph.AddEdge("1", "4")
+	graph.AddEdge("2", "5")
+	graph.AddEdge("2", "6")
+	graph.AddEdge("3", "6")
+	graph.AddEdge("4", "7")
+	graph.AddEdge("5", "7")
+	graph.AddEdge("6", "7")
+
+	fmt.Println("graph before computing:")
+	for _, e := range graph.Edges() {
+		fmt.Println("*", e)
+	}
+	fmt.Println()
+
+	result := ComputePert(graph)
+	fmt.Println("graph after computing:")
+	fmt.Println(result)
+	for _, e := range graph.Edges() {
+		fmt.Println("*", e)
+	}
+
 	// Output:
-	// * (1,2)[[pert:To=3,Tm=6,Tp=15,Te=7,σe=2,Ve=4,title:a]]
-	// * (1,3)[[pert:To=2,Tm=5,Tp=14,Te=6,σe=2,Ve=4,title:b]]
-	// * (1,4)[[pert:To=6,Tm=12,Tp=30,Te=14,σe=4,Ve=16,title:c]]
-	// * (2,5)[[pert:To=2,Tm=5,Tp=8,Te=5,σe=1,Ve=1,title:d]]
-	// * (2,6)[[pert:To=5,Tm=11,Tp=17,Te=11,σe=2,Ve=4,title:e]]
-	// * (3,6)[[pert:To=3,Tm=6,Tp=15,Te=7,σe=2,Ve=4,title:f]]
-	// * (4,7)[[pert:To=3,Tm=9,Tp=27,Te=11,σe=4,Ve=16,title:g]]
-	// * (5,7)[[pert:To=1,Tm=4,Tp=7,Te=4,σe=1,Ve=1,title:h]]
-	// * (6,7)[[pert:To=4,Tm=19,Tp=28,Te=18,σe=4,Ve=16,title:i]]
 }

vertex.go

@@ -26,6 +26,8 @@ func newVertex(id string, attrs ...Attrs) *Vertex {
 	var a Attrs
 	if len(attrs) > 0 {
 		a = attrs[0]
+	} else {
+		a = make(map[string]interface{})
 	}
 	return &Vertex{
 		id:           id,