added FlameGraph run script

run

@@ -0,0 +1,103 @@
+#!/usr/bin/env bash
+#
+# profile_flamegraph.sh
+#
+# Runs ./build/nufi_poisson under `perf record`, then converts the
+# result into a flamegraph. Run this from the project root (".").
+#
+# All profiling artifacts are written to ./results/perf/ so they don't
+# collide with the simulation's own output files in ./results/
+# (nufi_poisson clears regular files in "results/" at the start of
+# main(), see main.cc's clear_results_directory()).
+
+set -euo pipefail
+
+# ---- config -----------------------------------------------------------
+BINARY="./build/nufi_poisson"
+FLAMEGRAPH_DIR="${HOME}/.local/bin/FlameGraph"
+OUT_DIR="./results/perf"
+PERF_FREQ=99
+
+# ---- checks -------------------------------------------------------------
+if [[ ! -x "${BINARY}" ]]; then
+  echo "error: ${BINARY} not found or not executable. Build the project first." >&2
+  exit 1
+fi
+
+if [[ ! -x "${FLAMEGRAPH_DIR}/stackcollapse-perf.pl" ]] || [[ ! -x "${FLAMEGRAPH_DIR}/flamegraph.pl" ]]; then
+  echo "error: FlameGraph scripts not found under ${FLAMEGRAPH_DIR}" >&2
+  exit 1
+fi
+
+if ! command -v perf >/dev/null 2>&1; then
+  echo "error: 'perf' not found on PATH." >&2
+  exit 1
+fi
+
+# perf needs kernel.perf_event_paranoid low enough to record kernel symbols
+# and full call graphs. -1 is fully open; most distros default to 1-4.
+# This only sets it for the current boot (same effect as writing directly
+# to /proc/sys/kernel/perf_event_paranoid) -- it does NOT persist, and does
+# NOT touch /etc/sysctl.conf. Override the target with:
+#   PERF_EVENT_PARANOID=0 ./profile_flamegraph.sh
+PARANOID_PATH="/proc/sys/kernel/perf_event_paranoid"
+DESIRED_PARANOID="${PERF_EVENT_PARANOID:--1}"
+
+if [[ -r "${PARANOID_PATH}" ]]; then
+  CURRENT_PARANOID="$(cat "${PARANOID_PATH}")"
+  if [[ "${CURRENT_PARANOID}" -gt "${DESIRED_PARANOID}" ]]; then
+    echo "==> kernel.perf_event_paranoid is ${CURRENT_PARANOID}, lowering to ${DESIRED_PARANOID} (needs sudo) ..."
+    if ! sudo sysctl -w "kernel.perf_event_paranoid=${DESIRED_PARANOID}" >/dev/null; then
+      echo "warning: could not lower kernel.perf_event_paranoid -- kernel symbols/call graphs may be incomplete." >&2
+      echo "         you can set it manually with: sudo sysctl -w kernel.perf_event_paranoid=${DESIRED_PARANOID}" >&2
+    fi
+  fi
+fi
+
+mkdir -p "${OUT_DIR}"
+
+PERF_DATA="${OUT_DIR}/perf.data"
+PERF_SCRIPT_OUT="${OUT_DIR}/out.perf"
+FOLDED_OUT="${OUT_DIR}/out.folded"
+FLAMEGRAPH_OUT="${OUT_DIR}/flamegraph.svg"
+
+# ---- run ----------------------------------------------------------------
+echo "==> Recording with perf (-F ${PERF_FREQ}) ..."
+echo "    (Ctrl+C stops the binary early and still runs the rest of the pipeline)"
+
+# perf record catches SIGINT itself, finalizes perf.data, and exits -- but
+# bash's default non-interactive behavior is to terminate the *script* the
+# moment it sees SIGINT, and `set -e` would abort on perf record's non-zero
+# exit status anyway. Temporarily ignore SIGINT at the script level and
+# capture the exit code manually so an early Ctrl+C just moves on to
+# generating the flamegraph from whatever was captured.
+set +e
+trap '' SIGINT
+perf record -F "${PERF_FREQ}" -g -o "${PERF_DATA}" -- "${BINARY}"
+PERF_EXIT=$?
+trap - SIGINT
+set -e
+
+if [[ ${PERF_EXIT} -ne 0 ]]; then
+  echo "    (perf record exited with code ${PERF_EXIT}, likely from an interrupt -- continuing anyway)"
+fi
+
+if [[ ! -s "${PERF_DATA}" ]]; then
+  echo "error: ${PERF_DATA} is missing or empty, nothing to process." >&2
+  exit 1
+fi
+
+echo "==> Generating perf script output ..."
+perf script -i "${PERF_DATA}" > "${PERF_SCRIPT_OUT}"
+
+echo "==> Collapsing stacks ..."
+"${FLAMEGRAPH_DIR}/stackcollapse-perf.pl" "${PERF_SCRIPT_OUT}" > "${FOLDED_OUT}"
+
+echo "==> Building flamegraph ..."
+"${FLAMEGRAPH_DIR}/flamegraph.pl" "${FOLDED_OUT}" > "${FLAMEGRAPH_OUT}"
+
+echo "==> Done."
+echo "    perf.data   : ${PERF_DATA}"
+echo "    out.perf    : ${PERF_SCRIPT_OUT}"
+echo "    out.folded  : ${FOLDED_OUT}"
+echo "    flamegraph  : ${FLAMEGRAPH_OUT}"