Vamos falar de Concorrência

Por José Valim, na RubyConf Brasil 2012.

Transcript

1. CONCORRÊNCIA VAMOS FALAR SOBRE
3. Core Team Member
5. Executar duas ou mais tarefas de forma simultânea
6. Server Server Server Server
7. Server
8. MULTI CORE ÚNICO PROCESSO
9. estado concorrência off off
10. O modelo declarativo porque matemática rocks!
11. •não existe “mutação” •não existe concorrência •apenas funções
12. factorial = lambda do |x| case x when 0 1 else x * factorial.(x-1) end end print factorial.(10) # => 3628800
13. Determinismo As mesmas entradas => as mesmas saídas
14. •não existe random() •não existe I/O em disco •não existem efeitos colaterais •sempre o mesmo resultado
15. lambda do |a, b| c = expensive_function.(a) d = also_expensive.(b) c + d end
16. lambda do |a, b| c = expensive_function.(a) d = also_expensive.(b) c + d end a = 1
17. lambda do |1, b| c = 42 d = also_expensive.(b) c + d end
18. lambda do |a, b| c = expensive_function.(a) d = also_expensive.(b) c + d end
19. lambda do |a, b| d = also_expensive.(b) c = expensive_function.(a) c + d end
20. Haskell Usando determinismo para performance e expressividade
21. l = lambda { |a,b,c| a + b + c } l.(1, 2, 3) #=> 6 l.curry #=> #<Proc> l.curry.(1) #=> #<Proc> l.curry.(1).(2).(3) #=> 6 Currying
22. l = lambda { |a,b| a * b } double = l.curry.(2) triple = l.curry.(3) Currying
23. mult a b = a * b double = mult 2 (mult 2 3) ((mult 2) 3) Currying haskell
24. mult a b = a * b double = mult 2 double 3 haskell
25. mult a b = a * b double = mult 2 double 3 Compilador haskell
26. mult a b = a * b double = mult 2 double 3 Compilador (mult 2 3) haskell
27. CONCORRÊNCIA VAMOS ATIVAR
28. estado concorrência off on
29. Variáveis dataflow Concorrência sem dor!
30. lambda do |a, b| c = expensive_function.(a) d = also_expensive.(b) c + d end
31. lambda do |a, b| thread { c = expensive_function.(a) } thread { d = also_expensive.(b) } c + d end
32. main
33. main spawn thread 1
34. main spawn thread 1 spawn thread 2
35. main spawn thread 1 spawn thread 2 unbound c
36. main spawn thread 1 spawn thread 2 unbound c defines c
37. main spawn thread 1 spawn thread 2 unbound c defines c unbound d
38. main spawn thread 1 spawn thread 2 unbound c defines c unbound d defines d
39. main spawn thread 1 spawn thread 2 unbound c defines c unbound d defines d c + d
40. ESTADO VAMOS ATIVAR
41. estado concorrência on on
43. O PROBLEMA
44. class Counter mattr_accessor :i self.i = 0 end thread { Counter.i = Counter.i + 1 }
45. thread 1 Counter.i thread 2
46. thread 1 Counter.i thread 2 0
47. thread 1 Counter.i thread 2 0 0
48. thread 1 Counter.i thread 2 0 0 1
49. thread 1 Counter.i thread 2 0 0 1 1
50. thread 1 Counter.i thread 2 0 1 0 1 1
51. thread 1 Counter.i thread 2 0 1 0 1 1 1
52. thread 1 Counter.i thread 2 0 1 0 1 1 1 1
53. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 1
54. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 1 2
55. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 1 2 2
56. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 1 2 2 2
57. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 1 2 2 2 2
58. •shared-memory concurrent model •locks •transactional memory •message-passing concurrent model
59. •shared-memory concurrent model •locks •transactional memory •message-passing concurrent model
60. class Counter mattr_accessor :i self.i = 0 end thread { Counter.i = Counter.i + 1 }
61. class Counter mattr_accessor :i self.i = 0 end thread { synchronize { Counter.i = Counter.i + 1 } }
62. thread 1 Counter.i thread 2
63. thread 1 Counter.i thread 2 0
64. thread 1 Counter.i thread 2 0 0
65. thread 1 Counter.i thread 2 0 0 1
66. thread 1 Counter.i thread 2 0 0 1 1
67. thread 1 Counter.i thread 2 0 1 0 1 1
68. thread 1 Counter.i thread 2 0 1 0 1 1 1 synchronize {
69. thread 1 Counter.i thread 2 0 1 0 1 1 2 1 synchronize {
70. thread 1 Counter.i thread 2 0 1 0 1 1 2 1 synchronize { 2 }
71. thread 1 Counter.i thread 2 0 1 0 1 1 2 2 1 synchronize { 2 }
72. thread 1 Counter.i thread 2 0 1 0 1 1 2 2 2 1 synchronize { 2 }
73. thread 1 Counter.i thread 2 0 1 0 1 1 2 2 3 2 1 synchronize { 2 }
74. thread 1 Counter.i thread 2 0 1 0 1 1 2 2 3 3 2 1 synchronize { 2 }
75. + técnica mais popular + controle explícito sobre o lock
76. - controle explícito sobre o lock - técnica pessimista
77. •shared-memory concurrent model •locks •transactional memory •message-passing concurrent model
78. class Counter mattr_accessor :i self.i = ref { 0 } end thread { atomic { Counter.i = Counter.i + 1 } }
79. thread 1 Counter.i thread 2
80. thread 1 Counter.i thread 2 0
81. thread 1 Counter.i thread 2 0 0
82. thread 1 Counter.i thread 2 0 0 1
83. thread 1 Counter.i thread 2 0 0 1 1
84. thread 1 Counter.i thread 2 0 1 0 1 1
85. thread 1 Counter.i thread 2 0 1 0 1 1 1 atomic {
86. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 atomic {
87. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 1 atomic {
88. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 2 1 atomic {
89. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 2 2 1 atomic {
90. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 2 2 2 1 atomic {
91. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 2 2 2 1 atomic { }
92. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 2 2 2 1 atomic { }
93. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 2 2 2 1 atomic { }
94. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 2 2 2 2 1 atomic { }
95. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 2 2 2 2 2 1 atomic { }
96. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 2 2 2 2 2 3 1 atomic { }
97. thread 1 Counter.i thread 2 0 1 0 1 1 1 1 2 2 2 2 2 3 3 1 atomic { }
98. + técnica otimista + não possui deadlock nem condições de corrida
99. - tentativas desnecessárias - overhead com transações
100. •shared-memory concurrent model •locks •transactional memory •message-passing concurrent model
101. server = lambda do |i| receive when :increment server.(i+1) when :check client <- i server.(i) else warn "unknown message" server.(i) end end server.(0)
102. thread { server <- :increment }
103. client 1 server client 2
104. client 1 server client 2 0
105. client 1 server client 2 0 :increment
106. client 1 server client 2 0 1 :increment
107. client 1 server client 2 0 1 :increment :increment
108. client 1 server client 2 0 2 1 :increment :increment
109. client 1 server client 2 0 2 1 :increment :increment :increment
110. client 1 server client 2 0 2 1 3 :increment :increment :increment
111. client 1 server client 2 0 2 1 3 :increment :increment :increment :check
112. client 1 server client 2 0 2 1 3 3 :increment :increment :increment :check
113. client 1 server client 2 0 2 1 3 3 :increment :increment :increment :check
114. client 1 server client 2 0 2 1 3 3 3 :increment :increment :increment :check
115. “Do not communicate by sharing memory; instead, share memory by communicating;” Effective Go
116. + não precisa de sincronização + fácil de distribuir
117. - coordenação é difícil - modelagem não convencional
118. RESUMINDO
119. message-passing locks stm go, erlang ruby clojure dataflow oz
120. github.com/celluloid
121. @elixirlang / elixir-lang.org
122. É IMPORTANTE O COMPORTAMENTO DEFAULT
123. BALAS DE PRATA NÃO EXISTEM
124. REFERÊNCIAS Seven languages in seven weeks
125. Concepts, Techniques and Models of Computer Programming REFERÊNCIAS
126. REFERÊNCIAS Software Transactional Memory http://java.ociweb.com/mark/stm/article.html Persistent Data Structures http://www.infoq.com/presentations/Value-Identity-State-Rich-Hickey
127. http://plataformatec.com.br Estamos contratando!
129. ? PERGUNTAS José Valim @josevalim