#!/bin/bash

# smpqueue: Simple queue-based SMP shell scheduler
# Written by Patrice Levesque in 2008
# License: Public domain
#
# Invoke without arguments to get usage information
#
# Note that the scheduling queue is checked every second,
# so if execution time of your tasks is very short, this
# script will make total execution time higher.

SYSCPU='/sys/class/cpuid/'
WHICH=`which which 2> /dev/null` || { echo "Couldn't find 'which'.  Exiting"; exit 1; }
WC=`${WHICH} wc 2> /dev/null` || { echo "Couldn't find 'wc'.  Exiting"; exit 1; }
LS=`${WHICH} ls 2> /dev/null` || { echo "Couldn't find 'ls'.  Exiting"; exit 1; }
SLEEP=`${WHICH} sleep 2> /dev/null` || { echo "Couldn't find 'sleep'.  Exiting"; exit 1; }

NUMBER_OF_THREADS=`${LS} ${SYSCPU} | ${WC} -w`

PROGRAM_NAME=`basename "${0}"`

COMMAND="${1}"
shift
ALLARGS=''

# Help
if [ -z "${1}" -o "${1}" = "-h" -o "${1}" = "--help" ]; then
	echo -e "${PROGRAM_NAME}: Schedules repetitive tasks on SMP"
	echo
	echo -e "Usage:"
	echo -e "\t${PROGRAM_NAME} program arguments -- files"
	echo
	echo -e "Examples:"
	echo -e "\t${PROGRAM_NAME} oggenc --bitrate=192 -- *.wav"
	echo -e "\t${PROGRAM_NAME} md5sum -- *"
	echo -e "\t${PROGRAM_NAME} mogrify -resize 640x480 -- *.jpg"
	echo
	echo -e "(${NUMBER_OF_THREADS} processors detected on this machine)"
	exit 1;
fi

# Parse arguments
while true; do
	ARGS=${1}
	if [ ${ARGS} = '--' ]; then
		break;
	fi
	ALLARGS="${ALLARGS} ${ARGS}"
	shift
done

# Schedule the tasks
while true; do
	shift
	[ -z "${1}" ] && { wait; exit; }
	ENQUEUED=1
	while [ ${ENQUEUED} -eq 1 ]; do
		CURRENT_PROCESSES=`jobs | ${WC} -l`
		if [ ${CURRENT_PROCESSES} -lt ${NUMBER_OF_THREADS} ]; then
			${COMMAND} ${ALLARGS} "${1}" &
			ENQUEUED=0
		else
			${SLEEP} 1s
		fi
	done;
done;