HW2: RC3 - A small exchange optimization

homework_2/julia/bitonic_v1.jl

@@ -4,9 +4,9 @@
 #
 
 function exchange(localid,  remoteid)
-    if verbose
-        println("Exchange local data from $localid with partner $remoteid")
-    end
+    # if verbose
+    #     println("Exchange local data from $localid with partner $remoteid")
+    # end
     nothing # We have all data here ;)
 end
 
@@ -23,9 +23,89 @@ function minmax(data, localid, remoteid, keepsmall)
 end
 
 
+function is_bitonic(arr)
+    n = length(arr)
+    if n <= 2
+        return true # Any sequence of length <= 2 is bitonic
+    end
+
+    # State for state machine. 1: inc, -1: dec, 0: z-state
+    state = 0
+    inc_count = 0
+    dec_count = 0
+    ret = false
+
+    for i in 1:n-1
+        # Find the first order
+        if state == 0
+            if arr[i] > arr[i+1]
+                state = -1
+                dec_count += 1
+            elseif arr[i] < arr[i+1]
+                state = 1
+                inc_count += 1
+            end
+        elseif state == -1   # decreasing
+            if arr[i] < arr[i + 1]
+                state = 1
+                inc_count += 1
+            end
+        elseif state == 1   # increasing
+            if arr[i] > arr[i+1]
+                state = -1
+                dec_count += 1
+            end
+        end
+    end
+
+    if inc_count <= 1 && dec_count <= 1
+        ret =  true # Sequence is bitonic
+    elseif inc_count == 2 && dec_count == 1
+        ret =  (arr[1] >= arr[n])
+    elseif inc_count == 1 && dec_count == 2
+        ret = (arr[1] <= arr[n])
+    end
+
+    ret
+end
+
+function is_sort(arr)
+    # State for state machine. 1: inc, -1: dec, 0: z-state
+    state = 0
+    inc_count = 0
+    dec_count = 0
+
+    for i in 1:length(arr)-1
+        # Find the first order
+        if state == 0
+            if arr[i] > arr[i+1]
+                state = -1
+                dec_count += 1
+            elseif arr[i] < arr[i+1]
+                state = 1
+                inc_count += 1
+            end
+        elseif state == -1   # decreasing
+            if arr[i] < arr[i + 1]
+                state = 1
+                inc_count += 1
+            end
+        elseif state == 1   # increasing
+            if arr[i] > arr[i+1]
+                state = -1
+                dec_count += 1
+            end
+        end
+    end
+
+    ret =  ((inc_count + dec_count) == 1) ? state : 0
+    ret
+end
 
 function sort_network!(data, n, depth)
     nodes = 0:n-1
+    bitonicFlag = zeros(Int8, size(data, 1))
+    sortFlag    = zeros(Int8, size(data, 1))
     for step = depth-1:-1:0
         partnerid = nodes .⊻ (1 << step)
         direction = (nodes .& (1 << depth)) .== 0 .& (nodes .< partnerid)
@@ -40,6 +120,13 @@ function sort_network!(data, n, depth)
                 minmax(data, i, partnerid[i+1], keepsmall[i+1])
             end
         end
+        if verbose
+            for i in 1:size(data, 1)
+                bitonicFlag[i] = is_bitonic(data[i, :])
+                sortFlag[i] = is_sort(data[i, :])
+            end
+            println("depth: $depth | step: $step | bitonicFlag: $bitonicFlag | sorfFlag: $sortFlag")
+        end
     end
 end