# Pass the command you want to benchmark with various numbers of CPU cores on the command line.
#
# Examples
#
#   $ how_fast_do_various_numbers_of_cores_run "ffmpeg -f lavfi -i mandelbrot=s=1920x1080 -frames 50 -c:v libvpx -f null -"
#
#   $ how_fast_do_various_numbers_of_cores_run "ffmpeg -y -f lavfi -i mandelbrot=s=1920x1080 -threads 1 -row-mt 1 -frames 50 -c:v libvpx /tmp/bench.webm"
#
#   $ how_fast_do_various_numbers_of_cores_run "7z b"
# 
echo "CPU cores, elapsed time in seconds" > /tmp/core_benchmark.out             # Initialize report with column headings.
for CPU_cores in $( seq $( nproc) ) ; do                                        # Measure how long the command takes with different numbers of CPU cores.
    /usr/bin/time   -o /tmp/time.out                            \
                    -f "%e"                                     \
                    taskset -c 0-$(( $CPU_cores - 1 )) $@                       # Actually run the command on a certain number of cores.
    echo $CPU_cores,$(cat /tmp/time.out) >> /tmp/core_benchmark.out             # Record elapsed time for this many CPU cores.
    rm /tmp/time.out                                                            # Delete the file containing the elapsed time.
done
cat /tmp/core_benchmark.out                                                     # Report all results.