#!/usr/bin/env bash
# Keep some cores busy, standing in for heat and work competing with the program
# (a hot afternoon, the modem, something else running).
#
#   tools/thermal-sim/heat-load.sh 2 600     # 2 cores flat out for 10 minutes
#
# Uses stress-ng when installed; otherwise one busy shell loop per core. Ctrl-C
# stops it early. Needs no root.
set -euo pipefail

[[ $# -eq 2 && $1 =~ ^[0-9]+$ && $2 =~ ^[0-9]+$ ]] || {
    echo "usage: $0 <cores> <seconds>" >&2; exit 2; }
cores=$1 secs=$2

if command -v stress-ng >/dev/null; then
    exec stress-ng --cpu "$cores" --timeout "${secs}s" --metrics-brief
fi

echo "stress-ng not found; using $cores busy loop(s) for $secs s"
pids=()
trap 'kill "${pids[@]}" 2>/dev/null' EXIT INT TERM
for _ in $(seq "$cores"); do
    ( end=$((SECONDS + secs)); while (( SECONDS < end )); do :; done ) &
    pids+=($!)
done
wait