Mercurial > lbo > hg > localmr
view src/map.rs @ 50:603c38d64cd5
Experiment: Pre-fetch larger buffers from shards
author | Lewin Bormann <lbo@spheniscida.de> |
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date | Wed, 03 Feb 2016 21:15:39 +0000 |
parents | ab7d19e012e0 |
children | 07095d20ba5c |
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//! Implements the mapping phase. //! #![allow(dead_code)] use std::fmt; use std::io::Write; use std::collections::{LinkedList, BTreeMap}; use mapreducer::MapReducer; use record_types::{Record, MEmitter}; use parameters::MRParameters; use formats::util::MRSinkGenerator; type MapInput = LinkedList<Record>; /// This is the base of the mapping phase. It contains an input /// and intermediary input and output forms. /// Mapper threads run on this. Every mapper thread has one MapPartition /// instance per input chunk. struct MapPartition<MR: MapReducer, SinkGen: MRSinkGenerator> { mr: MR, params: MRParameters, input: MapInput, sink: SinkGen, sorted_input: BTreeMap<String, String>, sorted_output: BTreeMap<String, Vec<String>>, } impl<MR: MapReducer, SinkGen: MRSinkGenerator> MapPartition<MR, SinkGen> { pub fn _new(params: MRParameters, input: MapInput, mr: MR, output: SinkGen) -> MapPartition<MR, SinkGen> { MapPartition { mr: mr, params: params, input: input, sink: output, sorted_input: BTreeMap::new(), sorted_output: BTreeMap::new(), } } pub fn _run(mut self) { self.sort_input(); self.do_map(); self.write_output(); } /// Sorts input into the sorted_input map, moving the records on the way /// (so no copying happens and memory consumption stays low-ish) fn sort_input(&mut self) { loop { match self.input.pop_front() { None => break, Some(record) => { self.sorted_input.insert(record.key, record.value); } } } } /// Executes the mapping phase. fn do_map(&mut self) { let mut key_buffer = Vec::with_capacity(self.params.key_buffer_size); loop { for k in self.sorted_input.keys().take(self.params.key_buffer_size) { key_buffer.push(k.clone()) } for k in &key_buffer[..] { let val; match self.sorted_input.remove(k) { None => continue, Some(v) => val = v, } let mut e = MEmitter::new(); self.mr.map(&mut e, Record { key: k.clone(), value: val, }); self.insert_result(e); } if key_buffer.len() < self.params.key_buffer_size { break; } key_buffer.clear(); } } fn setup_output(&mut self) -> Vec<SinkGen::Sink> { // Set up sharded outputs. let mut outputs = Vec::new(); for i in 0..self.params.reducers { let out = self.sink.new_output(&fmt::format(format_args!("mapout_{}.{}", self.params.shard_id, i))); outputs.push(out); } assert_eq!(outputs.len(), self.params.reducers); outputs } fn write_output(&mut self) { let mut outputs = self.setup_output(); for (k, vs) in self.sorted_output.iter() { let shard = self.mr.shard(self.params.reducers, k); for v in vs { let r1 = outputs[shard].write(k.as_bytes()); match r1 { Err(e) => panic!("couldn't write map output: {}", e), Ok(_) => (), } let r2 = outputs[shard].write(v.as_bytes()); match r2 { Err(e) => panic!("couldn't write map output: {}", e), Ok(_) => (), } } } } fn insert_result(&mut self, emitter: MEmitter) { for r in emitter._get() { let e; { e = self.sorted_output.remove(&r.key); } match e { None => { self.sorted_output.insert(r.key, vec![r.value]); } Some(mut v) => { v.push(r.value); self.sorted_output.insert(r.key, v); } } } } } #[cfg(test)] mod tests { use closure_mr::ClosureMapReducer; use formats::util::RecordIterator; use formats::lines::LinesSinkGenerator; use map::MapPartition; use record_types::{MEmitter, REmitter, Record, MultiRecord}; use parameters::MRParameters; use std::collections::LinkedList; fn mapper_func(e: &mut MEmitter, r: Record) { for w in r.value.split_whitespace() { e.emit(String::from(w), String::from("1")); } } fn reducer_func(_: &mut REmitter, _: MultiRecord) { // no-op } fn get_mr() -> ClosureMapReducer { ClosureMapReducer::new(mapper_func, reducer_func) } fn get_input() -> LinkedList<Record> { let inp: Vec<String> = vec!["abc def", "xy yz za", "hello world", "let's do this", "foo bar baz"] .iter() .map(move |s| String::from(*s)) .collect(); let ri: RecordIterator<_> = RecordIterator::new(inp.into_iter()); ri.collect() } fn get_output() -> LinesSinkGenerator { LinesSinkGenerator::new(&String::from("test_map_")) } #[test] fn test_map_partition() { use std::fmt::format; use std::fs; let reducers = 3; let mp = MapPartition::_new(MRParameters::new().set_concurrency(4, reducers), get_input(), get_mr(), get_output()); mp._run(); for i in 0..reducers { let filename = format(format_args!("test_map_mapout_0.{}", i)); let _ = fs::remove_file(filename); } } }