forked from nytlabs/streamtools
/
zipf.go
86 lines (81 loc) · 2.13 KB
/
zipf.go
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package library
import (
"errors"
"github.com/nytlabs/streamtools/st/blocks" // blocks
"github.com/nytlabs/streamtools/st/util" // util
"math/rand"
)
// specify those channels we're going to use to communicate with streamtools
type Zipf struct {
blocks.Block
queryrule chan chan interface{}
inrule chan interface{}
inpoll chan interface{}
out chan interface{}
quit chan interface{}
}
// we need to build a simple factory so that streamtools can make new blocks of this kind
func NewZipf() blocks.BlockInterface {
return &Zipf{}
}
// Setup is called once before running the block. We build up the channels and specify what kind of block this is.
func (b *Zipf) Setup() {
b.Kind = "Zipf"
b.Desc = "draws a random number from a Zipf-Mandelbrot distribution when polled"
b.inrule = b.InRoute("rule")
b.queryrule = b.QueryRoute("rule")
b.inpoll = b.InRoute("poll")
b.quit = b.Quit()
b.out = b.Broadcast()
}
// Run is the block's main loop. Here we listen on the different channels we set up.
// this is actually the Zipf-Manadlebrot "law".
// http://en.wikipedia.org/wiki/Zipf%E2%80%93Mandelbrot_law
// the parameter `v` is denoted `q` on wikipedia.
func (b *Zipf) Run() {
var err error
var s, v, imax float64
s = 2.0
v = 5.0
imax = 99.0
r := rand.New(rand.NewSource(12345))
sampler := rand.NewZipf(r, s, v, uint64(imax))
for {
select {
case ruleI := <-b.inrule:
// set a parameter of the block
rule, ok := ruleI.(map[string]interface{})
if !ok {
b.Error(errors.New("couldn't assert rule to map"))
}
s, err = util.ParseFloat(rule, "s")
if err != nil {
b.Error(err)
}
v, err = util.ParseFloat(rule, "v")
if err != nil {
b.Error(err)
}
imax, err = util.ParseFloat(rule, "N")
if err != nil {
b.Error(err)
}
sampler = rand.NewZipf(r, s, v, uint64(imax))
case <-b.quit:
// quit the block
return
case <-b.inpoll:
// deal with a poll request
b.out <- map[string]interface{}{
"sample": float64(sampler.Uint64()),
}
case c := <-b.queryrule:
// deal with a query request
c <- map[string]interface{}{
"s": s,
"v": v,
"N": imax,
}
}
}
}