// doTest checks that Sample picks items evenly. "n" samples are
// drawn from a list of numbers of length "space". This is repeated
// "iters" times. The number of times a particular number is drawn
// should be within "tolerance" of the expected number.
func doTest(t *testing.T, n, space, iters int, tolerance float64) {
count := make([]int, space)
for i := 0; i < iters; i++ {
s := stream.Sequence(
stream.Numbers(0, space-1),
stream.SampleWithSeed(n, int64(i)),
)
stream.ForEach(s, func(s string) {
num := -1 // Will cause panic below if Scan fails
fmt.Sscan(s, &num)
count[num]++
})
}
// Check that all counts are approximately equal.
expected := (float64(iters) * float64(n)) / float64(space)
minExpected := expected * (1.0 - tolerance)
maxExpected := expected * (1.0 + tolerance)
for i, n := range count {
if float64(n) < minExpected || float64(n) > maxExpected {
t.Errorf("%d has %d samples; expected range [%f,%f]\n",
i, n, minExpected, maxExpected)
}
}
}
func ExampleSampleWithSeed() {
stream.Run(
stream.Numbers(1, 100),
stream.SampleWithSeed(2, 100),
stream.Sort().Num(1),
stream.WriteLines(os.Stdout),
)
// Output:
// 11
// 46
}