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// Copyright 2021 the Blobloom authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Bloomstat is a utility for estimating Bloom filter sizes.
package main
import (
"fmt"
"io"
"log"
"os"
"strconv"
"strings"
"github.com/greatroar/blobloom"
)
const usage = `usage: bloomstat capacity false-positive-rate [max-memory]
The maximum memory may be specified as "10MB", "1.5GiB", etc.`
func main() {
if len(os.Args) < 2 {
fmt.Fprintln(os.Stderr, usage)
os.Exit(1)
}
var (
capacity = parse("capacity", os.Args[1])
fpr = parse("false positive rate", os.Args[2])
maxsize float64
)
if len(os.Args) > 3 {
maxsize = parseMem(os.Args[3])
}
bits, hashes := blobloom.Optimize(blobloom.Config{
Capacity: uint64(capacity),
FPRate: fpr,
MaxBits: uint64(8 * maxsize),
})
size, unit := memsize(float64(bits))
bitsPerKey := float64(bits) / capacity
expectedFpr := blobloom.FPRate(uint64(capacity), bits, hashes)
fmt.Printf("%d bits, %.02f %s\n"+
"%.02f bits/%.02f B per key\n"+
"%d hashes\n"+
"%.04f expected false positive rate\n",
bits, size, unit, bitsPerKey, bitsPerKey/8, hashes, expectedFpr)
}
const (
kiB = 1 << 10
MiB = 1 << 20
GiB = 1 << 30
)
func memsize(bits float64) (size float64, unit string) {
size = float64(bits) / 8
switch {
case size >= GiB:
size /= GiB
unit = "GiB"
case size >= MiB:
size /= MiB
unit = "MiB"
case size >= kiB:
size /= kiB
unit = "kiB"
default:
unit = "B"
}
return
}
func parse(name, num string) float64 {
v, err := strconv.ParseFloat(num, 64)
switch e := err.(type) {
case nil:
case *strconv.NumError:
log.Fatalf("%s %q: %v", name, e.Num, e.Err)
default:
log.Fatalf("%s: %v", name, err)
}
if v < 0 {
log.Fatalf("%s must be >= 0", name)
}
return v
}
func parseMem(s string) float64 {
var (
size float64
unit string
)
n, err := fmt.Sscanf(s, "%f%s", &size, &unit)
switch err {
case nil:
case io.EOF:
if n == 1 {
// Default to bytes.
unit = "b"
} else {
log.Fatal("max memory: invalid input")
}
default:
log.Fatal("max memory:", err)
}
switch strings.ToLower(unit) {
case "kb", "kib":
size *= kiB
case "mb", "mib":
size *= MiB
case "gb", "gib":
size *= GiB
}
return size
}
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