Add exercise 8 and fix whitespace for no 5 from chapter 14

Author: Bernard Pietraga

chapter_14/working_with_multiple_processes_5_b.exs

@@ -1,4 +1,3 @@
-
 defmodule Linker4 do
   import :timer, only: [sleep: 1]
 

chapter_14/working_with_multiple_processes_8.ex

@@ -0,0 +1,74 @@
+defmodule FibSolver do
+  def fib(scheduler) do
+    send scheduler, {:ready, self()}
+    receive do
+      {:fib, n, client} ->
+        send client, {:answer, n, fib_calc(n), self()}
+        fib(scheduler)
+      {:shutdown} ->
+        exit(:normal)
+    end
+  end
+
+  defp fib_calc(0), do: 0
+  defp fib_calc(1), do: 1
+  defp fib_calc(n), do: fib_calc(n - 1) + fib_calc(n - 2)
+end
+
+defmodule Scheduler do
+  def run(num_processes, module, func, to_calculate) do
+    (1..num_processes)
+    |> Enum.map(fn(_) -> spawn(module, func, [self()]) end)
+    |> schedule_processes(to_calculate, [])
+  end
+
+  defp schedule_processes(processes, queue, results) do
+    receive do
+      {:ready, pid} when length(queue) > 0 ->
+        [next|tail] = queue
+        send pid, {:fib, next, self()}
+        schedule_processes(processes, tail, results)
+
+      {:ready, pid} ->
+        send pid, {:shutdown}
+        if length(processes) > 1 do
+          schedule_processes(List.delete(processes, pid), queue, results)
+        else
+          Enum.sort(results, fn {n1, _}, {n2, _} -> n1 <= n2 end)
+        end
+
+      {:answer, number, result, _pid} ->
+        schedule_processes(processes, queue, [{number, result} | results])
+    end
+  end
+end
+
+to_process = [37,37,37,37]
+
+Enum.each 1..10, fn num_processes ->
+  {time, result} = :timer.tc(
+    Scheduler, :run,
+    [num_processes, FibSolver, :fib, to_process]
+  )
+
+  if num_processes == 1 do
+    IO.puts inspect result
+    IO.puts "\n #    time (s)"
+  end
+
+  :io.format( "~2B     ~.2f~n", [num_processes, time/1000000.0])
+end
+
+# [{37, 24157817}, {37, 24157817}, {37, 24157817}, {37, 24157817}]
+
+#  #    time (s)
+#  1     6.36
+#  2     3.31
+#  3     3.55
+#  4     2.06
+#  5     1.95
+#  6     1.95
+#  7     1.88
+#  8     1.91
+#  9     2.10
+# 10     2.08