1 Sorting Networks

Sorting

3 Sorting Network (Bitonic Sorting Network)

4 Sorting Network (Bitonic Sorting Network)

5 Comparator x y max(x,y) min(x,y)

6 Comparator max min

7 Comparator max min

8

9 Levels 123 Depth = 3 Width = 4

Level 1

Level 2

Level 3

InputOutput

InputOutput

levels

17 Sort(n) Sort(n/2) Merge(n) In Out depth Recursive construction of Bitonic Sorting Network

18 Merge(n) Merge(n/2) depth Recursive construction of merging network

19 Induction Basis Sort(2) Merge(2)

20 Width Sorting network depth: Merger width Total depth

21 Counting Networks

22 The Counting Problem 0 Shared variable

23 0 Token = Increment request Shared variable

24 1 Increment request Shared variable 0

25 1 Shared variable

26 1 Increment request Shared variable

27 2 Shared variable 1 Increment request

28 2 Shared variable

29 2 Increment request Shared variable

30 3 Increment request Shared variable 2

31 6 Sequential Bottleneck Shared variable The requests have to be serialized

32 Counting Network Inputs Outputs

33 Counting Network

34 Balancer Inputs Outputs Token

35 Balancer Inputs Outputs

36 Balancer

37 Balancer

38 Balancer

39 Balancer

40 Balancer

41 Balancer

42 Balancer All tokens together

43 Balancer Step property

44 Balancer Step property Another example

45 Balancer Step property Another example

46 Balancer Step property Another example

47 Counting Network (Bitonic Counting Network)

48 Counting Network

49 Counting Network

50 Counting Network

51 Counting Network

52 Counting Network

53 Counting Network

54 Counting Network

55 Counting Network

56 Counting Network

57 Counting Network

58 Counting Network

59 Counting Network

60 Counting Network

61 Counting Network

62 Counting Network

63 Counting Network

64 Counting Network

65 Counting Network All tokens

66 Counting Network All tokensStep property

67 Counting Network Another example Step property

68 Counting Network Another example Step property

69 Counting Network Another example Step property

70 Counting Network Another example Step property

71 Counting Network Parallelism Many increment requests are processed simultaneously

72 Counting Token = Increment request Output Shared variables

73 Counting Output Shared variables

74 Counting Returned value Shared variable value is increased by 4 (output width)

75 Counting Increment request

76 Counting

77 Counting Returned value

78 Counting Increment request

79 Counting Returned value

80 Counting

81 Counting Returned value

82 Counting

83 Counting Returned value

84 Counting

85 Counting Returned value

86 Counting All tokens

87 Bitonic Counting Network Isomorphic to Bitonic Sorting Network

88 Count(n) Count(n/2) Merge(n) In Out depth

89 Merge(n) Merge1(n/2) Merge2(n/2) depth Step Prop. Step Prop. Step Prop.

90 Even subsequence Odd subsequence

91 Merge(n) Merge1(n/2) Merge2(n/2)

92 Theorem: Proof: The proof is by induction on For the merger is a balancer and the claim holds trivially. Induction Basis: The merger(n) produces output Z with step property if both inputs X and Y have step property

93 Induction Hypothesis: Merge(n/2) If step sequence Then step sequence Assume that every merger of size n/2 and smaller performs merging properly

94 Merge(n) Induction step: If step Then step We want to show that: Suppose and have the step property. Then we show that has the step property

95 If has the step property then and have the step property Tokens

96 Merge1(n/2) Merge2(n/2) step Therefore, from induction hypothesis: Output sequence

97 First, we show: Where denotes the total number of tokens in sequence

98 We have: Merger 1 Merger 2

99 or Since has the step property: Therefore: Similarly:

100

101 Now, we show that has the step property There is at most one wire where the two sequences differ #tokens step

102 Step property Merge1(n/2) Merge(n/2) Merge(n)