Parallelize search using multiple processes

This commit is a proof-of-concept implementation of parallelized search
to take advantage of multiple cores of the system. A multi-threaded
program written in Ruby cannot saturate more than a single core of CPU
because of GIL. So the only way we can use multiple cores is to spawn
multiple processes, split the work, and merge the partial results. The
result of each child process is passed to the parent via pipe in a
serialized form. This serialization and deserialization of the result is
the unavoidable overhead of using multiple processes instead of multiple
threads. Unfortunately, Ruby's default serialization method,
Marshal.dump is found to be so slow that it often shadows the gain
especially when the selectivity of the query is not very good. So in
this implementation I chose to use MessagePack which is at least 5-times
faster than Marshal. However, this will make installing fzf much
trickier for many people. So I'm not sure if I want to merge this code
into the master branch considering that fzf is already pretty fast in
most cases thanks to its caching scheme and the benefit of
parallelization is only noticeable when the list has more than 50k
items.

fzf

@@ -7,7 +7,7 @@
 #  / __/ / /_/ __/
 # /_/   /___/_/    Fuzzy finder for your shell
 #
-# Version: 0.8.3 (April 3, 2014)
+# Version: 0.9.0-alpha (April 21, 2014)
 #
 # Author:  Junegunn Choi
 # URL:     https://github.com/junegunn/fzf
@@ -39,6 +39,7 @@
 require 'thread'
 require 'curses'
 require 'set'
+require 'msgpack'
 
 unless String.method_defined? :force_encoding
   class String
@@ -74,6 +75,16 @@ class FZF
     end
   end
 
+  # TODO
+  def cores?
+    cores = `sysctl -n hw.physicalcpu 2> /dev/null`.chomp
+    if $?.exitstatus == 0
+      cores.to_i
+    else
+      1
+    end
+  end
+
   def initialize argv, source = $stdin
     @rxflag   = nil
     @sort     = ENV.fetch('FZF_DEFAULT_SORT', 1000).to_i
@@ -88,6 +99,9 @@ class FZF
     @filter   = nil
     @nth      = nil
     @delim    = nil
+    @pids     = []
+    @procs    = cores?
+    @parallel_min = 10000
 
     argv =
       if opts = ENV['FZF_DEFAULT_OPTS']
@@ -148,6 +162,16 @@ class FZF
         @sort = $1.to_i
       when '-e', '--extended-exact'    then @extended = :exact
       when '+e', '--no-extended-exact' then @extended = nil
+      when '-p', '--parallel'
+        usage 1, 'number of processes required' unless pnum = argv.shift
+        @procs = pnum.to_i
+      when /^-p([1-9][0-9]*)$/, /^--parallel=([1-9][0-9]*)$/
+        @procs = $1.to_i
+      when '--parallel-min'
+        usage 1, 'number of processes required' unless pmin = argv.shift
+        @parallel_min = pmin.to_i
+      when /^--parallel-min=([1-9][0-9]*)$/
+        @parallel_min = $1.to_i
       else
         usage 1, "illegal option: #{o}"
       end
@@ -223,7 +247,7 @@ class FZF
   end
 
   def filter_list list
-    matches = matcher.match(list, @filter, '', '')
+    matches = matcher.match(list, @filter)
     if @sort && matches.length <= @sort
       matches = FZF.sort(matches)
     end
@@ -667,6 +691,103 @@ class FZF
     end
   end
 
+  def cached lists, q, prefix, suffix
+    cnt = 0
+    cached = lists.inject({}) do |sum, l|
+      cached = matcher.cached(l, q, prefix, suffix)
+      cnt += cached ? cached.length : l.length
+      sum[l] = cached
+      sum
+    end
+    [cnt, cached]
+  end
+
+  def search lists, q, cx
+    cache_count, cached = cached(lists, q, q[0, cx], q[cx..-1])
+    if @procs <= 1 || lists.empty? || lists.length < @procs || cache_count < @parallel_min
+      search_sequential lists, q, cached
+    else
+      search_parallel lists, q, cached
+    end
+  end
+
+  def search_sequential lists, q, cached
+    progress   = 0
+    started_at = Time.now
+
+    found = []
+    skip  = false
+    cnt   = 0
+    lists.each do |list|
+      cnt += list.length
+      skip = @mtx.synchronize { @events[:key] }
+      break if skip
+
+      if (progress = 100 * cnt / @count.get) < 100 && Time.now - started_at > 0.5
+        render { print_info " (#{progress}%)" }
+      end
+      matches = matcher.match(list, q, cached[list])
+      matcher.cache list, q, matches
+      found.concat matches
+    end
+    return :skip if skip
+    found
+  end
+
+  def search_parallel lists, q, cached
+    list_map = lists.inject({}) { |h, l| h[l.object_id] = l; h }
+    slice_size = lists.length / @procs
+    slices = lists.each_slice(slice_size)
+
+    triples = slices.map do |lists|
+      read, write = IO.pipe
+      [fork do
+        read.close
+        running = true
+        Signal.trap('USR1') do
+          running = false
+        end
+        matches = {}
+        lists.each do |list|
+          break unless running
+          matches[list.object_id] = matcher.match(list, q, cached[list])
+        end
+        write << MessagePack.pack(matches)
+        exit! running
+      end, read, write]
+    end
+
+    matches = []
+    @pids = triples.map { |t| t.first }
+    mutex = Mutex.new
+    skip = false
+    triples.map { |pid, read, write|
+      Thread.new do
+        write.close
+        result = read.read
+        _, status = Process.wait2(pid)
+        raise if result.empty?
+        if status.exitstatus == 0
+          MessagePack.unpack(result).each do |list_object_id, data|
+            mutex.synchronize do
+              matches.concat data
+            end
+            matcher.cache list_map[list_object_id], q, data
+          end
+        else
+          skip = true
+        end
+      end
+    }.each(&:join)
+    skip ? :skip : matches
+  end
+
+  def signal_children
+    while pid = @pids.pop
+      Process.kill 'USR1', pid rescue nil
+    end
+  end
+
   def start_search &callback
     Thread.new do
       lists   = []
@@ -704,39 +825,26 @@ class FZF
 
           new_search = events[:key] || events.delete(:new)
           user_input = events[:key]
-          progress   = 0
-          started_at = Time.now
 
           if updated = new_search && !lists.empty?
-            q, cx = events.delete(:key) || [q, 0]
+            q, cx     = events.delete(:key) || [q, 0]
-            empty = matcher.empty?(q)
             unless matches = fcache[q]
-              found = []
+              # Simply concats the list
-              skip  = false
+              if matcher.empty?(q)
-              cnt   = 0
+                matches = lists.inject([]) { |cc, l| cc.concat l }
-              lists.each do |list|
+              else
-                cnt += list.length
+                matches ||= search(lists, q, cx)
-                skip = @mtx.synchronize { @events[:key] }
+                next if matches == :skip
-                break if skip
+                matches = @sort ? matches : matches.reverse
-
+                if @sort && matches.length <= @sort
-                if !empty && (progress = 100 * cnt / @count.get) < 100 && Time.now - started_at > 0.5
+                  matches = FZF.sort(matches)
-                  render { print_info " (#{progress}%)" }
                 end
-
-                found.concat(q.empty? ? list :
-                             matcher.match(list, q, q[0, cx], q[cx..-1]))
               end
-              next if skip
-              matches = @sort ? found : found.reverse
-              if !empty && @sort && matches.length <= @sort
-                matches = FZF.sort(matches)
-              end
-              fcache[q] = matches
             end
 
             # Atomic update
-            @matches.set matches
+            @matches.set fcache[q] = matches
-          end#new_search
+          end
 
           callback = nil if callback &&
                             (updated || events[:loaded]) &&
@@ -1083,7 +1191,10 @@ class FZF
           upd = actions.fetch(key, actions[:default]).call(key)
 
           # Dispatch key event
-          emit(:key) { [@query.set(input.dup), cursor] } if upd
+          if upd
+            signal_children
+            emit(:key) { [@query.set(input.dup), cursor] }
+          end
         end
       end
     ensure
@@ -1176,9 +1287,7 @@ class FZF
       end
     end
 
-    def match list, q, prefix, suffix
+    def cached list, q, prefix, suffix
-      regexp = fuzzy_regex q
-
       cache = @caches[list.object_id]
       prefix_cache = nil
       (prefix.length - 1).downto(1) do |len|
@@ -1190,10 +1299,17 @@ class FZF
         break if suffix_cache = cache[suffix[idx..-1]]
       end unless suffix.empty?
 
-      partial_cache = [prefix_cache,
+      [prefix_cache, suffix_cache].compact.sort_by { |e| e.length }.first
-                       suffix_cache].compact.sort_by { |e| e.length }.first
+    end
-      cache[q] ||= (partial_cache ?
+
-                    partial_cache.map { |e| e.first } : list).map { |line|
+    def cache list, q, data
+      @caches[list.object_id][q] = data
+    end
+
+    def match list, q, partial_cache = nil
+      regexp = fuzzy_regex q
+
+      (partial_cache ? partial_cache.map { |e| e.first } : list).map { |line|
         # Ignore errors: e.g. invalid byte sequence in UTF-8
         md = do_match(line, regexp)
         md && [line, [md.offset(0)]]
@@ -1249,7 +1365,11 @@ class FZF
       Regexp.new(sanitize(Regexp.escape(w)), rxflag_for(w))
     end
 
-    def match list, q, prefix, suffix
+    def cache list, q, data
+      @caches[list.object_id][Set[parse q]] = data
+    end
+
+    def cached list, q, prefix, suffix
       regexps = parse q
       # Look for prefix cache
       cache  = @caches[list.object_id]
@@ -1258,10 +1378,12 @@ class FZF
       (prefix.length - 1).downto(1) do |len|
         break if prefix_cache = cache[Set[@regexps[prefix[0, len]]]]
       end
+      prefix_cache
+    end
 
-      cache[Set[regexps]] ||= (prefix_cache ?
+    def match list, q, partial_cache = nil
-                               prefix_cache.map { |e| e.first } :
+      regexps = parse q
-                               list).map { |line|
+      (partial_cache ? partial_cache.map { |e| e.first } : list).map { |line|
         offsets = []
         regexps.all? { |pair|
           regexp, invert = pair