Mercurial > hg
annotate mercurial/ancestor.py @ 15292:7fa471248185 stable
discovery: Fix error print mentioning a 'None' branch
When talking to old server discovery use heads of the 'None' branch to refer to
topological heads. This use of None should never make it to the end user.
author | Pierre-Yves David <pierre-yves.david@logilab.fr> |
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date | Mon, 17 Oct 2011 11:37:59 +0200 |
parents | 1ffeeb91c55d |
children | 0b03454abae7 |
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1 # ancestor.py - generic DAG ancestor algorithm for mercurial |
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2 # |
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3 # Copyright 2006 Matt Mackall <mpm@selenic.com> |
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4 # |
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5 # This software may be used and distributed according to the terms of the |
10263 | 6 # GNU General Public License version 2 or any later version. |
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7 |
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8 import heapq |
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9 |
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10 def ancestor(a, b, pfunc): |
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11 """ |
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12 Returns the common ancestor of a and b that is furthest from a |
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13 root (as measured by longest path) or None if no ancestor is |
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14 found. If there are multiple common ancestors at the same |
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15 distance, the first one found is returned. |
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16 |
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17 pfunc must return a list of parent vertices for a given vertex |
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18 """ |
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19 |
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20 if a == b: |
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21 return a |
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22 |
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23 a, b = sorted([a, b]) |
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24 |
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25 # find depth from root of all ancestors |
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26 # depth is stored as a negative for heapq |
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27 parentcache = {} |
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28 visit = [a, b] |
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29 depth = {} |
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30 while visit: |
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31 vertex = visit[-1] |
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32 pl = pfunc(vertex) |
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33 parentcache[vertex] = pl |
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34 if not pl: |
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35 depth[vertex] = 0 |
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36 visit.pop() |
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37 else: |
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38 for p in pl: |
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39 if p == a or p == b: # did we find a or b as a parent? |
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40 return p # we're done |
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41 if p not in depth: |
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42 visit.append(p) |
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43 if visit[-1] == vertex: |
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44 # -(maximum distance of parents + 1) |
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45 depth[vertex] = min([depth[p] for p in pl]) - 1 |
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46 visit.pop() |
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47 |
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48 # traverse ancestors in order of decreasing distance from root |
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49 def ancestors(vertex): |
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50 h = [(depth[vertex], vertex)] |
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51 seen = set() |
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52 while h: |
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53 d, n = heapq.heappop(h) |
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54 if n not in seen: |
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55 seen.add(n) |
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56 yield (d, n) |
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57 for p in parentcache[n]: |
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58 heapq.heappush(h, (depth[p], p)) |
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59 |
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60 def generations(vertex): |
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61 sg, s = None, set() |
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62 for g, v in ancestors(vertex): |
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63 if g != sg: |
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64 if sg: |
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65 yield sg, s |
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66 sg, s = g, set((v,)) |
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67 else: |
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68 s.add(v) |
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69 yield sg, s |
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70 |
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71 x = generations(a) |
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72 y = generations(b) |
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73 gx = x.next() |
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74 gy = y.next() |
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75 |
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76 # increment each ancestor list until it is closer to root than |
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77 # the other, or they match |
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78 try: |
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79 while True: |
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80 if gx[0] == gy[0]: |
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81 for v in gx[1]: |
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82 if v in gy[1]: |
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83 return v |
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84 gy = y.next() |
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85 gx = x.next() |
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86 elif gx[0] > gy[0]: |
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87 gy = y.next() |
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88 else: |
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89 gx = x.next() |
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90 except StopIteration: |
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91 return None |