[or-cvs] r20933: {projects} Add comments (projects/performance/node-selection)

[sjm217@xxxxxxxx]

Author: sjm217
Date: 2009-11-09 06:51:33 -0500 (Mon, 09 Nov 2009)
New Revision: 20933

Modified:
   projects/performance/node-selection/hillclimbing.py
Log:
Add comments

Modified: projects/performance/node-selection/hillclimbing.py
===================================================================
--- projects/performance/node-selection/hillclimbing.py	2009-11-09 11:39:11 UTC (rev 20932)
+++ projects/performance/node-selection/hillclimbing.py	2009-11-09 11:51:33 UTC (rev 20933)
@@ -15,10 +15,14 @@
 
 ## Number of iterations before narrowing adjustment
 ILIMIT = 1000
+## Maximum number of iterations before exiting
 NUM=8000
+## Fraction of network capacity which is being used (set to None to
+## use actual network data
+USAGE=0.5
 
 def wait(x, p, L, isbroken):
-    '''Calculate waiting time at each node'''
+    '''Calculate waiting time at each node (assuming M/D/1 queue)'''
     z = p*L*x
     a = z*x
     b = 2.0*(1.0-z)
@@ -30,14 +34,7 @@
     ## Check that probabilities really add up to 1
     assert abs(1.0 - prob.sum()) < 1e-6
 
-    ## Calculate processing time of a node
-    #xs = [1.0/t for t in nodebw]
-    #xs = 1.0/nodebw
-
     ## Find overloaded nodes
-    #loading_factor = [x*p*totalusage for p, x in zip(prob, xs)]
-    #broken = [ld < 0.0 or ld > 1.0 for ld in loading_factor]
-
     loading_factor = xs*prob*totalusage
     broken = (loading_factor < 0.0) | (loading_factor > 1.0)
     if broken.any():
@@ -46,30 +43,19 @@
     #print "Broken", len([x for x in broken if x])
 
     ## Calculate weighted waiting time
-    #wtime = [wait(x, p, totalusage, isbroken)
-    #          for x, p, isbroken in zip(xs, prob, broken)]
     wtime = wait(xs, prob, totalusage, False)
     wtime[broken] = -1.0
-    #print wtime[0]
 
     ## Get maximimum waiting time for non-broken nodes
     cap = wtime.max()
-    #if debug:
-    #    print cap
-    #print wtime
-    #print "Cap", cap
 
-    ## Calculated capped weighted waiting time
+    ## Calculate capped weighted waiting time
     wtime[broken] = cap
     wwtime = wtime * prob
-        
-    #wwtime = [wwait_cap(w, p, cap) for w, p in zip(wtime, prob)]
     
     return wwtime
 
-def test(fn = None):
-    if fn is None:
-        fn = sys.argv[1]
+def load_data(fn):
     fh = file(fn, "rt")
 
     ## Load in node bandwidths and total network usage
@@ -87,22 +73,18 @@
         totalbw += bw
         nodebw.append(bw)
 
-    #print totalusage, totalbw
+    # Node selection probabilities
+    pu = array([1.0/len(nodebw)] * len(nodebw)) # uniform
+    pt = array([bw / totalbw for bw in nodebw]) # Tor
 
-    pu = array([1.0/len(nodebw)] * len(nodebw))
-    pt = array([bw / totalbw for bw in nodebw])
-
     anodebw = array(nodebw)
     xs = 1.0/anodebw
+
+    ## Weighted waiting time for Tor and uniform weighting
     x = calc_waittime(pt, xs, totalusage, True)
     y = calc_waittime(pu, xs, totalusage, True)
 
-    #for i in range(10000):
-    #    _ = calc_waittime(pt, xs, totalusage)
-        
-    #print x
     print "E(Tor)", sum(x)
-    #print y
     print "E(Uniform)", sum(y)
 
     return totalusage, anodebw, x,y
@@ -175,32 +157,45 @@
         line, = self.ax.plot(wwait.cumsum())
         amount = 1.0/2
 
+        ## Main optimization loop
         i = 0
-        while i<NUM:
+        while i < NUM:
             i += 1
             cnt, self.prob, wwait, s = optimize(self.prob, s, self.xs, self.totalusage, amount)
             print "%6d %4d %f"%(i, cnt, s)
             if cnt > ILIMIT:
+                ## We tried for too long to optimize so reduce the
+                ## amount to modify probabilities
                 amount /= 2.0
                 print "Narrowing... to", amount
                 save(self.anodebw, self.prob, self.xs, self.totalusage, i)
                 
             line.set_ydata(cumsum(wwait))
             self.fig.canvas.draw()
-            #time.sleep(1)
+        ## Save the intermediate result
         save(self.anodebw, self.prob, self.xs, self.totalusage, i)
         sys.exit()
 
 def main():
-    totalusage, anodebw, x, y = test()
+    if len(sys.argv) != 2:
+        print "Usage: hillclimbing.py FILE"
+        sys.exit()
 
+    ## Load data file, where each line is:
+    ##  BANDWIDTH USAGE
+    ## Where both are in kB/s
+    fn = sys.argv[1]
+    totalusage, anodebw, x, y = load_data(fn)
+
+    ## Try for different levels of bandwidth usage
     #totalusage = anodebw.sum()*(1-1e-6)
     #totalusage = anodebw.sum()*(1-1e-3)
     #totalusage = anodebw.sum()*(1-1e-1)
     #totalusage = anodebw.sum()*(0.75)
     #totalusage = anodebw.sum()*(0.5)
     #totalusage = anodebw.sum()*(0.25)
-    totalusage = anodebw.sum()*(0.1)
+    if USAGE != None:
+        totalusage = anodebw.sum()*USAGE
     
     pt = anodebw/anodebw.sum()
     
@@ -208,6 +203,7 @@
     fig = plt.figure()
     ax = fig.add_subplot(111)
 
+    ## Optimize selection probabilities
     anim = Animator(pt, totalusage, anodebw, fig, ax)
 
     win = fig.canvas.manager.window
@@ -218,5 +214,4 @@
 if __name__=="__main__":
     main()
 
-
-
+# vim: ai ts=4 sts=4 et sw=4