From 84f420e2c5f0626904e094ff93b3ce322780901e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Joakim=20Frosteg=C3=A5rd?= <joakim.frostegard@gmail.com>
Date: Wed, 26 Oct 2022 20:03:59 +0200
Subject: [PATCH] udp bench: use gamma distribution for torrent selection

---
 aquatic_udp_bench/src/announce.rs |  6 +++---
 aquatic_udp_bench/src/common.rs   | 10 ++++++----
 aquatic_udp_bench/src/scrape.rs   |  6 +++---
 3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/aquatic_udp_bench/src/announce.rs b/aquatic_udp_bench/src/announce.rs
index e048bf4..9302764 100644
--- a/aquatic_udp_bench/src/announce.rs
+++ b/aquatic_udp_bench/src/announce.rs
@@ -5,7 +5,7 @@ use aquatic_common::CanonicalSocketAddr;
 use crossbeam_channel::{Receiver, Sender};
 use indicatif::ProgressIterator;
 use rand::Rng;
-use rand_distr::Pareto;
+use rand_distr::Gamma;
 
 use aquatic_udp::common::*;
 use aquatic_udp_protocol::*;
@@ -81,14 +81,14 @@ pub fn create_requests(
     info_hashes: &[InfoHash],
     number: usize,
 ) -> Vec<(AnnounceRequest, CanonicalSocketAddr)> {
-    let pareto = Pareto::new(1., PARETO_SHAPE).unwrap();
+    let gamma = Gamma::new(GAMMA_SHAPE, GAMMA_SCALE).unwrap();
 
     let max_index = info_hashes.len() - 1;
 
     let mut requests = Vec::new();
 
     for _ in 0..number {
-        let info_hash_index = pareto_usize(rng, pareto, max_index);
+        let info_hash_index = gamma_usize(rng, gamma, max_index);
 
         let request = AnnounceRequest {
             connection_id: ConnectionId(0),
diff --git a/aquatic_udp_bench/src/common.rs b/aquatic_udp_bench/src/common.rs
index f444166..e3885d0 100644
--- a/aquatic_udp_bench/src/common.rs
+++ b/aquatic_udp_bench/src/common.rs
@@ -1,8 +1,10 @@
 use indicatif::{ProgressBar, ProgressStyle};
 use rand::Rng;
-use rand_distr::Pareto;
+use rand_distr::Gamma;
+
+pub const GAMMA_SHAPE: f64 = 0.2;
+pub const GAMMA_SCALE: f64 = 100.0;
 
-pub const PARETO_SHAPE: f64 = 0.1;
 pub const NUM_INFO_HASHES: usize = 10_000;
 
 pub fn create_progress_bar(name: &str, iterations: u64) -> ProgressBar {
@@ -12,8 +14,8 @@ pub fn create_progress_bar(name: &str, iterations: u64) -> ProgressBar {
     ProgressBar::new(iterations).with_style(style)
 }
 
-pub fn pareto_usize(rng: &mut impl Rng, pareto: Pareto<f64>, max: usize) -> usize {
-    let p: f64 = rng.sample(pareto);
+pub fn gamma_usize(rng: &mut impl Rng, gamma: Gamma<f64>, max: usize) -> usize {
+    let p: f64 = rng.sample(gamma);
     let p = (p.min(101.0f64) - 1.0) / 100.0;
 
     (p * max as f64) as usize
diff --git a/aquatic_udp_bench/src/scrape.rs b/aquatic_udp_bench/src/scrape.rs
index e233779..0a1229f 100644
--- a/aquatic_udp_bench/src/scrape.rs
+++ b/aquatic_udp_bench/src/scrape.rs
@@ -5,7 +5,7 @@ use aquatic_common::CanonicalSocketAddr;
 use crossbeam_channel::{Receiver, Sender};
 use indicatif::ProgressIterator;
 use rand::Rng;
-use rand_distr::Pareto;
+use rand_distr::Gamma;
 
 use aquatic_udp::common::*;
 use aquatic_udp_protocol::*;
@@ -93,7 +93,7 @@ pub fn create_requests(
     number: usize,
     hashes_per_request: usize,
 ) -> Vec<(ScrapeRequest, CanonicalSocketAddr)> {
-    let pareto = Pareto::new(1., PARETO_SHAPE).unwrap();
+    let gamma = Gamma::new(GAMMA_SHAPE, GAMMA_SCALE).unwrap();
 
     let max_index = info_hashes.len() - 1;
 
@@ -103,7 +103,7 @@ pub fn create_requests(
         let mut request_info_hashes = Vec::new();
 
         for _ in 0..hashes_per_request {
-            let info_hash_index = pareto_usize(rng, pareto, max_index);
+            let info_hash_index = gamma_usize(rng, gamma, max_index);
             request_info_hashes.push(info_hashes[info_hash_index])
         }