Ignore main.exe if I'm lazy about go build

.gitignore

@@ -0,0 +1 @@
+main/main.exe

auctionsim/summary.go

@@ -0,0 +1,139 @@
+package auctionsim
+
+import (
+	"math"
+	"strconv"
+)
+
+// Digits of precision in floating-point values in CSVs.
+const CSVPrecision = 10
+
+/**
+ * ResultSummary contains notable results of an auction.
+ */
+type ResultSummary struct {
+	/// The number of bidders in the auction.
+	Bidders int
+	/// The price the item sold for.
+	Price float64
+	/// The amount of value the winner actually got out of the auctioned item.
+	WinnerValue float64
+	/// The highest bid the auction winner was willing to make.
+	WinnerMaxBid float64
+	/**
+	 * The amount by which the winner's value of the item exceeded the price
+	 * they paid. Often negative.
+	 */
+	WinnerProfit float64
+	/**
+	 * Number of losing bidders who had a "true value" of the item in excess
+	 * of the price paid.
+	 */
+	LosersWithRegrets int
+	/// The most the item was genuinely worth to any bidder.
+	HighestValue float64
+	/// The most the bidder with the highest value would have been willing to pay.
+	HighestValuatorBid float64
+	/**
+	 * How much the bidder with the highest value would have made in profit had
+	 * they won the auction for the price the auction's actual winner paid.
+	 * Often negative, indicating nobody would have made money on the auction.
+	 * If this is zero or negative, there are 0 losers with regrets.
+	 */
+	MissedProfit float64
+	/**
+	 * How much more valuable the item was to the bidder with the highest value
+	 * than it was to the auction's eventual winner, irrespective of winning bid.
+	 */
+	ValueDelta float64
+	/**
+	 * The rank of the bidder who actually had the highest value of the item.
+	 * The winner of the auction has rank 1. If all bidders had a true value of
+	 * negative infinity for the item, this will be greater than the number of
+	 * bidders.
+	 */
+	HighestValueRank int
+}
+
+/**
+ * Summarize takes an already-sorted list of bidders (see RunAuctionVerbosely)
+ * and the winning auction price, and calculates a ResultSummary for that auction.
+ */
+func Summarize(price float64, allBidders []Bidder) *ResultSummary {
+	regrets := 0
+	maxValue := math.Inf(-1)
+	maxIdx := -1
+
+	for i, b := range allBidders {
+		if b.Value > maxValue {
+			maxValue = b.Value
+			maxIdx = i
+		}
+		if b.Value > price {
+			regrets++
+		}
+	}
+
+	winner := allBidders[len(allBidders)-1]
+	rube := Bidder{Value: math.Inf(-1)}
+	if maxIdx >= 0 {
+		rube = allBidders[maxIdx]
+	}
+	return &ResultSummary{
+		Bidders:            len(allBidders),
+		Price:              price,
+		WinnerValue:        winner.Value,
+		WinnerMaxBid:       winner.BidCeiling(),
+		WinnerProfit:       winner.Value - price,
+		LosersWithRegrets:  regrets,
+		HighestValue:       maxValue,
+		HighestValuatorBid: rube.BidCeiling(),
+		MissedProfit:       rube.Value - price,
+		ValueDelta:         maxValue - winner.Value,
+		HighestValueRank:   len(allBidders) - maxIdx,
+	}
+}
+
+/**
+ * ResultSummaryCSVHeader returns column labels for the records emitted by
+ * (*ResultSummary).CSVRecord().
+ */
+func ResultSummaryCSVHeader() []string {
+	return []string{
+		"Bidders",
+		"Price",
+		"WinnerValue",
+		"WinnerMaxBid",
+		"WinnerProfit",
+		"LosersWithRegrets",
+		"HighestValue",
+		"HighestValuatorBid",
+		"MissedProfit",
+		"ValueDelta",
+		"HighestValueRank",
+	}
+}
+
+func csvFloat(f float64) string {
+	return strconv.FormatFloat(f, 'g', CSVPrecision, 64)
+}
+
+/**
+ * CSVRecord returns rows intended for use with encoding/csv.Writer, with
+ * columns in the order specified by ResultSummaryCSVHeader().
+ */
+func (s *ResultSummary) CSVRecord() []string {
+	return []string{
+		strconv.Itoa(s.Bidders),
+		csvFloat(s.Price),
+		csvFloat(s.WinnerValue),
+		csvFloat(s.WinnerMaxBid),
+		csvFloat(s.WinnerProfit),
+		strconv.Itoa(s.LosersWithRegrets),
+		csvFloat(s.HighestValue),
+		csvFloat(s.HighestValuatorBid),
+		csvFloat(s.MissedProfit),
+		csvFloat(s.ValueDelta),
+		strconv.Itoa(s.HighestValueRank),
+	}
+}

main/main.go

@@ -1,43 +1,130 @@
 package main
 
 import (
+	"encoding/csv"
+	"flag"
 	"fmt"
-	"log"
-	"os"
-	"strconv"
 	"git.chromaticdragon.app/kistaro/auctionsim/auctionsim"
+	"log"
+	"math"
+	"math/rand"
+	"os"
+	"strings"
 )
 
-func main() {
-	num := 1000
-	if len(os.Args) > 1 {
-		n, err := strconv.ParseInt(os.Args[1], 0, 64)
-		if err != nil {
-			log.Fatalf("can't parse %q as a number of bidders: %v", os.Args[1], err)
-		}
-		num = n
-	}
-	if num <= 1 {
-		log.Fatalf("can't run an auction with %d bidders", num)
-	}
+var (
+	bidders = flag.Int("b", 1000, "Number of bidders in each auction.")
+	runs    = flag.Int("r", 1, "Number of auctions to run.")
 
-	price, bidder := auctionsim.RunAuction(
-		auctionsim.CappedBidderGenerator{
-			G: auctionsim.NormalestBidderGenerator(),
-			Lim: num,
-		},
-	)
+	errorDev  = flag.Float64("d", 1.0, "Standard deviation of bidder irrationality.")
+	errorMean = flag.Float64("m", 0.0, "Mean of bidder irrationality. Negative values represent a bias towards underbidding.")
 
-	delta := bidder.Value - price
-	valueStr := "gaining nothing"
+	format = flag.String("f", "txt", "Output format: plain text (\"txt\") or CSV (\"csv\").")
+)
+
+func deltaStr(delta float64) string {
 	if delta > 0 {
-		valueStr = fmt.Sprintf("gaining ¤%f", delta)
+		return fmt.Sprintf("gained ¤%f", delta)
 	}
 	if delta < 0 {
-		valueStr = fmt.Sprintf("losing ¤%f", -delta)
+		return fmt.Sprintf("lost ¤%f", -delta)
+	}
+	return "broken even"
+}
+
+func normalizeFormat() error {
+	*format = strings.ToLower(*format)
+	if *format == "txt" {
+		return nil
+	}
+	if *format == "csv" {
+		return nil
+	}
+	return fmt.Errorf("unrecognized format: %q", *format)
+}
+
+type emitter interface {
+	Emit(*auctionsim.ResultSummary)
+	Flush()
+}
+
+type textEmitter struct {
+	notFirst bool
+}
+
+func (t *textEmitter) Emit(summary *auctionsim.ResultSummary) {
+	if t.notFirst {
+		fmt.Println()
+		fmt.Println("-----------------")
+		fmt.Println()
+	}
+	t.notFirst = true
+	fmt.Printf("The auction winner paid ¤%f. They have %s.\n", summary.Price, deltaStr(summary.WinnerProfit))
+	fmt.Printf("The item was worth ¤%f to them.\n", summary.WinnerValue)
+	fmt.Printf("They would have paid up to ¤%f for it.\n", summary.WinnerMaxBid)
+
+	fmt.Println()
+	if summary.LosersWithRegrets < 1 {
+		fmt.Println("The item was not worth that to anybody.")
+	} else {
+		fmt.Printf("The item was worth that to %d bidders, who stopped bidding too soon.\n", summary.LosersWithRegrets)
 	}
 
-	fmt.Printf("The auction winner paid ¤%f, %s.\n", price, valueStr)
-	fmt.Printf("The item was worth ¤%f to them.\n", bidder.Value)
-	fmt.Printf("They would have paid up to ¤%f for it.\n", bidder.BidCeiling())
+	fmt.Println()
+	if summary.HighestValueRank > summary.Bidders {
+		fmt.Println("Wow! It was infinitely beyond worthless to everybody.")
+	} else {
+		fmt.Printf("The bidder who would have gotten the most value was outbid by %d bidders.\n", summary.HighestValueRank-1)
+		fmt.Printf("The item was worth at most ¤%f to them. Their maximum bid was ¤%f.\n", summary.HighestValue, summary.HighestValuatorBid)
+		fmt.Printf("If they had paid the winning bid, they would have %s.\n", deltaStr(summary.MissedProfit))
+		fmt.Printf("They valued it ¤%f more than the winning bidder.\n", summary.ValueDelta)
+	}
+}
+
+func (*textEmitter) Flush() {}
+
+type csvEmitter struct {
+	w *csv.Writer
+}
+
+func (c *csvEmitter) Emit(summary *auctionsim.ResultSummary) {
+	c.w.Write(summary.CSVRecord())
+}
+
+func (c *csvEmitter) Flush() {
+	c.w.Flush()
+}
+
+func main() {
+	flag.Parse()
+
+	if err := normalizeFormat(); err != nil {
+		log.Fatal(err)
+	}
+
+	e := emitter(&textEmitter{})
+	if *format == "csv" {
+		w := csv.NewWriter(os.Stdout)
+		e = &csvEmitter{w}
+		w.Write(auctionsim.ResultSummaryCSVHeader())
+	}
+	defer e.Flush()
+
+	for i := 0; i < *runs; i++ {
+		g := &auctionsim.BiddersFromDistributions{
+			Values: auctionsim.NormalestDistribution(),
+			Irrationalities: &auctionsim.NormalDistribution{
+				Rand:   rand.New(rand.NewSource(int64(rand.Uint64()))),
+				StdDev: *errorDev,
+				Mean:   *errorMean,
+			},
+			Bankrolls: auctionsim.ConstDistribution(math.Inf(1)),
+		}
+		e.Emit(auctionsim.Summarize(auctionsim.RunAuctionVerbosely(
+			&auctionsim.CappedBidderGenerator{
+				G:   g,
+				Lim: int64(*bidders),
+			},
+		)))
+	}
 }