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optimize_test.go
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optimize_test.go
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// Copyright 2020 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.
package blobloom
import (
"fmt"
"math"
"testing"
"github.com/stretchr/testify/assert"
)
func TestFPRate(t *testing.T) {
t.Parallel()
// FP rate is zero when no keys have been inserted.
assert.EqualValues(t, 0, FPRate(0, 100, 3))
// FP rate is close to one when the capacity is greatly exceeded.
nhashes := 100.0 * math.Ln2
assert.InDelta(t, 1.0, FPRate(1e9, 1e8, int(nhashes)), 1e-7)
// Examples from Putze et al., page 4.
// XXX We compute 0.023041, which is confirmed by PARI/GP and SciPy.
// Is the rounding in the paper off?
assert.InDelta(t, 0.0231, FPRate(1, 8, 5), 6e-5)
// XXX This one is only accurate to one digit.
// The required number does not occur in the series expansion either,
// the closest partial sum being 1.9536e-4.
assert.InDelta(t, 1.94e-4, FPRate(1, 20, 14), 3e-5)
}
func TestFPRateConvergence(t *testing.T) {
for _, c := range []struct {
c, k float64
iter int
}{
{.01, 1, 2500},
{.1, 1, 2000},
{3, 2, 200},
{4, 2, 200},
{6, 3, 200},
{8, 5, 200},
{20, 14, 100},
{30, 20, 100},
} {
t.Run(fmt.Sprintf("c=%f,k=%d", c.c, int(c.k)), func(t *testing.T) {
t.Parallel()
fpr, iterations := fpRate(c.c, c.k)
t.Logf("fpr = %f", fpr)
assert.Less(t, iterations, c.iter)
})
}
}
func TestFPRateCorrectC(t *testing.T) {
t.Parallel()
// Try to reconstruct the correction table. We may be one bit off.
for i, expect := range correctC[1:] {
c := float64(i + 1)
k := float64(c) * math.Ln2
fprBlock := math.Exp(logFprBlock(c, k))
cprime := c
for {
if p, _ := fpRate(cprime, k); p <= fprBlock {
break
}
cprime++
k = cprime * math.Ln2
}
assert.InDelta(t, float64(expect), cprime, 1)
}
}
func TestFPRateInvalidInput(t *testing.T) {
assert.Panics(t, func() { FPRate(10, 0, 2) })
assert.Panics(t, func() { FPRate(10, 2, 0) })
}
func TestNewOptimizedMaxFPR(t *testing.T) {
t.Parallel()
f := NewOptimized(Config{
Capacity: 0,
FPRate: 1,
})
assert.EqualValues(t, BlockBits, f.NumBits())
}
func TestMaxBits(t *testing.T) {
t.Parallel()
for _, c := range []struct {
want, expect uint64
}{
{1, BlockBits},
{BlockBits - 1, BlockBits},
{BlockBits + 1, BlockBits},
{2*BlockBits - 1, BlockBits},
{4<<20 - 1, 4<<20 - BlockBits},
{4<<20 + 1, 4 << 20},
{4<<20 + BlockBits, 4<<20 + BlockBits},
} {
nbits, nhashes := Optimize(Config{
// Ask for tiny FPR with a huge number of keys.
Capacity: 2 * c.want,
FPRate: 1e-10,
MaxBits: c.want,
})
// Optimize should round down to multiple of BlockBits.
assert.LessOrEqual(t, nbits, c.expect)
assert.EqualValues(t, 0, nbits%BlockBits)
f := New(nbits, nhashes)
assert.Equal(t, c.expect, f.NumBits())
}
}
func TestOptimizeFewBits(t *testing.T) {
t.Parallel()
for _, config := range []Config{
{
Capacity: 1,
FPRate: .99,
MaxBits: 1,
},
{
Capacity: 100000,
FPRate: 0.01,
MaxBits: 408,
},
} {
// Optimize should give nbits >= BlockBits.
nbits, nhashes := Optimize(config)
assert.EqualValues(t, BlockBits, nbits)
assert.Greater(t, nhashes, 0)
}
}
func TestOptimizeInvalidFPRate(t *testing.T) {
t.Parallel()
assert.Panics(t, func() { Optimize(Config{FPRate: 0}) })
assert.Panics(t, func() { Optimize(Config{FPRate: 1.0000001}) })
}