From: Matt Joiner <anacrolix@gmail.com>
Date: Fri, 19 Dec 2014 23:07:41 +0000 (+1100)
Subject: Add some tools for analysing bloom filter use
X-Git-Tag: v1.0.0~1391
X-Git-Url: http://www.git.stargrave.org/?a=commitdiff_plain;h=e6c93455b5b018ba40c5bad20717fa7e6e6660be;p=btrtrc.git

Add some tools for analysing bloom filter use
---

diff --git a/internal/cmd/bloom-estimate/main.go b/internal/cmd/bloom-estimate/main.go
new file mode 100644
index 00000000..e05071e1
--- /dev/null
+++ b/internal/cmd/bloom-estimate/main.go
@@ -0,0 +1,15 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"github.com/willf/bloom"
+)
+
+func main() {
+	n := flag.Int("n", 0, "expected number of items")
+	falsePositiveRate := flag.Float64("fpr", 0, "false positive rate")
+	flag.Parse()
+	filter := bloom.NewWithEstimates(uint(*n), *falsePositiveRate)
+	fmt.Printf("m: %d, k: %d\n", filter.Cap(), filter.K())
+}
diff --git a/internal/cmd/bloom-false-positives/main.go b/internal/cmd/bloom-false-positives/main.go
new file mode 100644
index 00000000..d25ea17e
--- /dev/null
+++ b/internal/cmd/bloom-false-positives/main.go
@@ -0,0 +1,30 @@
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"github.com/willf/bloom"
+	"os"
+)
+
+func main() {
+	m := flag.Uint("m", 0, "")
+	k := flag.Uint("k", 0, "")
+	flag.Parse()
+	filter := bloom.New(*m, *k)
+	scanner := bufio.NewScanner(os.Stdin)
+	n := 0
+	collisions := 0
+	for scanner.Scan() {
+		if filter.TestAndAdd(scanner.Bytes()) {
+			collisions++
+		}
+		n++
+	}
+	if err := scanner.Err(); err != nil {
+		fmt.Fprintf(os.Stderr, "error reading stdin: %s", err)
+		os.Exit(1)
+	}
+	fmt.Printf("collisions %d/%d (%f)\n", collisions, n, float64(collisions)/float64(n)*100)
+}