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"""Example for generating an arbitrary DAG as a dependency map.
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This demo uses networkx to generate the graph.
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Authors
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-------
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* MinRK
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"""
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import networkx as nx
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from random import randint, random
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from IPython.zmq.parallel import client as cmod
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def randomwait():
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import time
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from random import random
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time.sleep(random())
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return time.time()
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def random_dag(nodes, edges):
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"""Generate a random Directed Acyclic Graph (DAG) with a given number of nodes and edges."""
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G = nx.DiGraph()
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for i in range(nodes):
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G.add_node(i)
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while edges > 0:
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a = randint(0,nodes-1)
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b=a
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while b==a:
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b = randint(0,nodes-1)
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G.add_edge(a,b)
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if nx.is_directed_acyclic_graph(G):
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edges -= 1
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else:
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# we closed a loop!
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G.remove_edge(a,b)
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return G
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def add_children(G, parent, level, n=2):
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"""Add children recursively to a binary tree."""
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if level == 0:
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return
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for i in range(n):
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child = parent+str(i)
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G.add_node(child)
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G.add_edge(parent,child)
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add_children(G, child, level-1, n)
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def make_bintree(levels):
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"""Make a symmetrical binary tree with @levels"""
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G = nx.DiGraph()
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root = '0'
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G.add_node(root)
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add_children(G, root, levels, 2)
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return G
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def submit_jobs(client, G, jobs):
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"""Submit jobs via client where G describes the time dependencies."""
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results = {}
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for node in nx.topological_sort(G):
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deps = [ results[n].msg_ids[0] for n in G.predecessors(node) ]
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results[node] = client.apply(jobs[node], after=deps)
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return results
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def validate_tree(G, times):
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"""Validate that jobs executed after their dependencies."""
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for node in G:
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t = times[node]
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for parent in G.predecessors(node):
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pt = times[parent]
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assert t > pt, "%s should have happened after %s"%(node, parent)
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def main(nodes, edges):
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"""Generate a random graph, submit jobs, then validate that the
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dependency order was enforced.
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Finally, plot the graph, with time on the x-axis, and
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in-degree on the y (just for spread). All arrows must
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point at least slightly to the right if the graph is valid.
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"""
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print "building DAG"
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G = random_dag(nodes, edges)
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jobs = {}
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msg_ids = {}
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times = {}
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pos = {}
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for node in G:
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jobs[node] = randomwait
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client = cmod.Client('tcp://127.0.0.1:10101')
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print "submitting tasks"
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results = submit_jobs(client, G, jobs)
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print "waiting for results"
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client.barrier()
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print "done"
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for node in G:
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times[node] = results[node].get()
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pos[node] = (times[node], G.in_degree(node)+random())
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validate_tree(G, times)
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nx.draw(G, pos)
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return G,times,msg_ids
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if __name__ == '__main__':
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import pylab
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main(32,128)
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pylab.show()
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