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common/rand: Remove exponential distribution functions (#1979)

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We were computing these functions incorrectly.
I'm not sure what distribution these numbers are, but it isn't the
normal exponential distribution. (We're making the probability of
getting a number of a particular bitlength equal, but the number in
that bitlength thats gets chosen is uniformly chosen)

We weren't using these functions anywhere in our codebase, and they
had a nomenclature error. (There aren't exponentially distributed
integers, instead they would be geometrically distributed)
This commit is contained in:
Dev Ojha
2018-07-16 00:19:08 -07:00
committed by Anton Kaliaev
parent a3df06d081
commit 71859f8f3b
3 changed files with 5 additions and 50 deletions
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47
libs/common/random.go
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@@ -109,18 +109,6 @@ func RandInt63n(n int64) int64 {
return grand.Int63n(n)
}
func RandUint16Exp() uint16 {
return grand.Uint16Exp()
}
func RandUint32Exp() uint32 {
return grand.Uint32Exp()
}
func RandUint64Exp() uint64 {
return grand.Uint64Exp()
}
func RandFloat32() float32 {
return grand.Float32()
}
@@ -247,39 +235,6 @@ func (r *Rand) Int63n(n int64) int64 {
return i63n
}
// Distributed pseudo-exponentially to test for various cases
func (r *Rand) Uint16Exp() uint16 {
bits := r.Uint32() % 16
if bits == 0 {
return 0
}
n := uint16(1 << (bits - 1))
n += uint16(r.Int31()) & ((1 << (bits - 1)) - 1)
return n
}
// Distributed pseudo-exponentially to test for various cases
func (r *Rand) Uint32Exp() uint32 {
bits := r.Uint32() % 32
if bits == 0 {
return 0
}
n := uint32(1 << (bits - 1))
n += uint32(r.Int31()) & ((1 << (bits - 1)) - 1)
return n
}
// Distributed pseudo-exponentially to test for various cases
func (r *Rand) Uint64Exp() uint64 {
bits := r.Uint32() % 64
if bits == 0 {
return 0
}
n := uint64(1 << (bits - 1))
n += uint64(r.Int63()) & ((1 << (bits - 1)) - 1)
return n
}
func (r *Rand) Float32() float32 {
r.Lock()
f32 := r.rand.Float32()
@@ -295,7 +250,7 @@ func (r *Rand) Float64() float64 {
}
func (r *Rand) Time() time.Time {
return time.Unix(int64(r.Uint64Exp()), 0)
return time.Unix(int64(r.Uint64()), 0)
}
// Bytes returns n random bytes generated from the internal