Mercurial > hg
annotate mercurial/ancestor.py @ 12709:4147a292c508
filectx: use ctx.size comparisons to speed up ctx.cmp
Comparing sizes is cheaper than comparing file contents, as it does not
involve reading the file on disk or from the filelog.
It is however not always possible: some extensions, or encode filters,
change data when extracting it to the working directory.
author | Nicolas Dumazet <nicdumz.commits@gmail.com> |
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date | Tue, 27 Jul 2010 23:07:30 +0900 |
parents | 4cdaf1adafc8 |
children | 22565ddb28e7 |
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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 return a minimal-distance ancestor of nodes a and b, or None if there is no |
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13 such ancestor. Note that there can be several ancestors with the same |
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14 (minimal) distance, and the one returned is arbitrary. |
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15 |
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16 pfunc must return a list of parent vertices for a given vertex |
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17 """ |
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18 |
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19 if a == b: |
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20 return a |
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21 |
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22 a, b = sorted([a, b]) |
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23 |
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24 # find depth from root of all ancestors |
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25 parentcache = {} |
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26 visit = [a, b] |
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27 depth = {} |
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28 while visit: |
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29 vertex = visit[-1] |
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30 pl = pfunc(vertex) |
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31 parentcache[vertex] = pl |
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32 if not pl: |
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33 depth[vertex] = 0 |
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34 visit.pop() |
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35 else: |
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36 for p in pl: |
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37 if p == a or p == b: # did we find a or b as a parent? |
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38 return p # we're done |
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39 if p not in depth: |
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40 visit.append(p) |
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41 if visit[-1] == vertex: |
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42 depth[vertex] = min([depth[p] for p in pl]) - 1 |
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43 visit.pop() |
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44 |
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45 # traverse ancestors in order of decreasing distance from root |
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46 def ancestors(vertex): |
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47 h = [(depth[vertex], vertex)] |
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48 seen = set() |
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49 while h: |
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50 d, n = heapq.heappop(h) |
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51 if n not in seen: |
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52 seen.add(n) |
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53 yield (d, n) |
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54 for p in parentcache[n]: |
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55 heapq.heappush(h, (depth[p], p)) |
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56 |
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57 def generations(vertex): |
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58 sg, s = None, set() |
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59 for g, v in ancestors(vertex): |
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60 if g != sg: |
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61 if sg: |
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62 yield sg, s |
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63 sg, s = g, set((v,)) |
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64 else: |
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65 s.add(v) |
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66 yield sg, s |
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67 |
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68 x = generations(a) |
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69 y = generations(b) |
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70 gx = x.next() |
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71 gy = y.next() |
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72 |
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73 # increment each ancestor list until it is closer to root than |
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74 # the other, or they match |
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75 try: |
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76 while 1: |
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77 if gx[0] == gy[0]: |
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78 for v in gx[1]: |
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79 if v in gy[1]: |
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80 return v |
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81 gy = y.next() |
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82 gx = x.next() |
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83 elif gx[0] > gy[0]: |
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84 gy = y.next() |
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85 else: |
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86 gx = x.next() |
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87 except StopIteration: |
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88 return None |