cpi

#!/bin/bash

LIMIT_METHOD=duration # set this to "quantity" or "duration"
#LIMIT_METHOD=quantity # set this to "quantity" or "duration"
TRIAL_LIMIT=100 # number of trials to evaluate (per core) if LIMIT_METHOD==quantity
DURATION_LIMIT=15 # duration in seconds to run if LIMIT_METHOD==duration
CACHE_SIZE=1200 # number of trials to cache before flushing to bc -- used for tuning; 1000 seems near-optimal
SCALE=10 # scale for bc

PROCS=$(grep -c "^processor[[:space:]]\+:" /proc/cpuinfo)

calc() {
	case $1 in
		quantity)
			while [[ ${counter} -lt ${TRIAL_LIMIT} ]]; do
				string+="(${RANDOM}/32768)^2+(${RANDOM}/32768)^2<=1;"
				if [[ $(( ++counter % CACHE_SIZE )) -eq 0 ]]; then
					echo "$(bc -l <<<"scale=${SCALE};${string}" | grep -c 1):${CACHE_SIZE}"
					unset string
				fi
			done
		;;
		duration)
			while [[ ${SECONDS} -lt ${DURATION_LIMIT} ]]; do
				string+="(${RANDOM}/32767)^2+(${RANDOM}/32767)^2<=1;"
				if [[ $(( ++counter % CACHE_SIZE )) -eq 0 ]]; then
					echo "$(bc -l <<<"scale=${SCALE};${string}" | grep -c 1):${CACHE_SIZE}"
					unset string
				fi
			done
		;;
		*)
			break
		;;
	esac
	[[ -n "${string}" ]] && echo "$(bc -l <<<"scale=${SCALE};${string}" | grep -c 1):$(( counter % CACHE_SIZE ))"
}

parallelCalc() {
	for (( proc=0; ${proc} < ${PROCS}; proc++ )); do
		calc ${LIMIT_METHOD} &
	done
	wait
}


for result in $(parallelCalc); do
	((results+=${result%:*}))
	((trials+=${result#*:}))
done
echo -ne "Trial count: ${trials}\nPi estimate: "
bc -l <<<"scale=${SCALE};${results}/(${trials})*4" | sed "s/0\+$//"