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/* NOTE: Requires mongo shell to be built with V8 javascript engine,
which implements concurrent threads via fork() */
// Fork and start
function fork_(thunk) {
thread = fork(thunk)
thread.start()
return thread
}
// In functional form, useful for high-order functions like map in fun.js
function join_(thread) {thread.join()}
// Fork a loop on each one-arg block and wait for all of them to terminate. Foreground blocks are executed n times, background blocks are executed repeatedly until all forground loops finish. If any fail, stop all loops and reraise exception in main thread
function parallel(n, foregroundBlock1s, backgroundBlock1s) {
var err = null
var stop = false
function loop(m) {return function(block1) {return function() {
for (var i = 0; i < m; i++) {if (stop) break; block1(i)} }}}
function watch(block) {return function() {
try {block()} catch(e) {err = e; stop = true}}}
foreThunks = map(watch, map(loop(n), foregroundBlock1s))
backThunks = map(watch, map(loop(Infinity), backgroundBlock1s))
foreThreads = map(fork_, foreThunks)
backThreads = map(fork_, backThunks)
map(join_, foreThreads)
stop = true
map(join_, backThreads)
if (err != null) throw err
}
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