From 4634ac484a03f88f716429712504e7c354441c0b Mon Sep 17 00:00:00 2001
From: Tyler Neely <tylerneely@gmail.com>
Date: Wed, 12 Oct 2022 18:19:06 +0200
Subject: [PATCH] Optimize simulator RNG usage (#590)
This causes instructions for `basic_request.cpp` to drop from 281 million to 28 million
---
src/io/simulator/simulator_handle.cpp | 6 ++----
src/io/simulator/simulator_handle.hpp | 2 ++
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/src/io/simulator/simulator_handle.cpp b/src/io/simulator/simulator_handle.cpp
index fe4bc8c1f..9fa16fae3 100644
--- a/src/io/simulator/simulator_handle.cpp
+++ b/src/io/simulator/simulator_handle.cpp
@@ -73,8 +73,7 @@ bool SimulatorHandle::MaybeTickSimulator() {
// We tick the clock forward when all servers are blocked but
// there are no in-flight messages to schedule delivery of.
- std::poisson_distribution<> time_distrib(50);
- Duration clock_advance = std::chrono::microseconds{time_distrib(rng_)};
+ const Duration clock_advance = std::chrono::microseconds{time_distrib_(rng_)};
cluster_wide_time_microseconds_ += clock_advance;
MG_ASSERT(cluster_wide_time_microseconds_ < config_.abort_time,
@@ -93,8 +92,7 @@ bool SimulatorHandle::MaybeTickSimulator() {
auto [to_address, opaque_message] = std::move(in_flight_.back());
in_flight_.pop_back();
- std::uniform_int_distribution<int> drop_distrib(0, 99);
- const int drop_threshold = drop_distrib(rng_);
+ const int drop_threshold = drop_distrib_(rng_);
const bool should_drop = drop_threshold < config_.drop_percent;
if (should_drop) {
diff --git a/src/io/simulator/simulator_handle.hpp b/src/io/simulator/simulator_handle.hpp
index 7ad1d795a..3adf2b7b0 100644
--- a/src/io/simulator/simulator_handle.hpp
+++ b/src/io/simulator/simulator_handle.hpp
@@ -51,6 +51,8 @@ class SimulatorHandle {
std::set<Address> blocked_on_receive_;
std::set<Address> server_addresses_;
std::mt19937 rng_;
+ std::uniform_int_distribution<int> time_distrib_{5, 50};
+ std::uniform_int_distribution<int> drop_distrib_{0, 99};
SimulatorConfig config_;
void TimeoutPromisesPastDeadline() {