[9] | 1 | /* ========================================================================= */ |
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| 2 | /* === AMD_post_tree ======================================================= */ |
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| 3 | /* ========================================================================= */ |
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| 4 | |
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| 5 | /* ------------------------------------------------------------------------- */ |
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| 6 | /* AMD, Copyright (c) Timothy A. Davis, */ |
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| 7 | /* Patrick R. Amestoy, and Iain S. Duff. See ../README.txt for License. */ |
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| 8 | /* email: davis at cise.ufl.edu CISE Department, Univ. of Florida. */ |
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| 9 | /* web: http://www.cise.ufl.edu/research/sparse/amd */ |
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| 10 | /* ------------------------------------------------------------------------- */ |
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| 11 | |
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| 12 | /* Post-ordering of a supernodal elimination tree. */ |
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| 13 | |
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| 14 | #include "amd_internal.h" |
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| 15 | |
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| 16 | GLOBAL Int AMD_post_tree |
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| 17 | ( |
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| 18 | Int root, /* root of the tree */ |
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| 19 | Int k, /* start numbering at k */ |
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| 20 | Int Child [ ], /* input argument of size nn, undefined on |
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| 21 | * output. Child [i] is the head of a link |
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| 22 | * list of all nodes that are children of node |
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| 23 | * i in the tree. */ |
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| 24 | const Int Sibling [ ], /* input argument of size nn, not modified. |
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| 25 | * If f is a node in the link list of the |
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| 26 | * children of node i, then Sibling [f] is the |
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| 27 | * next child of node i. |
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| 28 | */ |
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| 29 | Int Order [ ], /* output order, of size nn. Order [i] = k |
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| 30 | * if node i is the kth node of the reordered |
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| 31 | * tree. */ |
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| 32 | Int Stack [ ] /* workspace of size nn */ |
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| 33 | #ifndef NDEBUG |
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| 34 | , Int nn /* nodes are in the range 0..nn-1. */ |
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| 35 | #endif |
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| 36 | ) |
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| 37 | { |
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| 38 | Int f, head, h, i ; |
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| 39 | |
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| 40 | #if 0 |
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| 41 | /* --------------------------------------------------------------------- */ |
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| 42 | /* recursive version (Stack [ ] is not used): */ |
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| 43 | /* --------------------------------------------------------------------- */ |
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| 44 | |
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| 45 | /* this is simple, but can caouse stack overflow if nn is large */ |
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| 46 | i = root ; |
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| 47 | for (f = Child [i] ; f != EMPTY ; f = Sibling [f]) |
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| 48 | { |
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| 49 | k = AMD_post_tree (f, k, Child, Sibling, Order, Stack, nn) ; |
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| 50 | } |
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| 51 | Order [i] = k++ ; |
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| 52 | return (k) ; |
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| 53 | #endif |
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| 54 | |
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| 55 | /* --------------------------------------------------------------------- */ |
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| 56 | /* non-recursive version, using an explicit stack */ |
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| 57 | /* --------------------------------------------------------------------- */ |
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| 58 | |
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| 59 | /* push root on the stack */ |
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| 60 | head = 0 ; |
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| 61 | Stack [0] = root ; |
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| 62 | |
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| 63 | while (head >= 0) |
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| 64 | { |
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| 65 | /* get head of stack */ |
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| 66 | ASSERT (head < nn) ; |
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| 67 | i = Stack [head] ; |
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| 68 | AMD_DEBUG1 (("head of stack "ID" \n", i)) ; |
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| 69 | ASSERT (i >= 0 && i < nn) ; |
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| 70 | |
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| 71 | if (Child [i] != EMPTY) |
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| 72 | { |
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| 73 | /* the children of i are not yet ordered */ |
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| 74 | /* push each child onto the stack in reverse order */ |
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| 75 | /* so that small ones at the head of the list get popped first */ |
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| 76 | /* and the biggest one at the end of the list gets popped last */ |
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| 77 | for (f = Child [i] ; f != EMPTY ; f = Sibling [f]) |
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| 78 | { |
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| 79 | head++ ; |
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| 80 | ASSERT (head < nn) ; |
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| 81 | ASSERT (f >= 0 && f < nn) ; |
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| 82 | } |
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| 83 | h = head ; |
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| 84 | ASSERT (head < nn) ; |
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| 85 | for (f = Child [i] ; f != EMPTY ; f = Sibling [f]) |
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| 86 | { |
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| 87 | ASSERT (h > 0) ; |
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| 88 | Stack [h--] = f ; |
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| 89 | AMD_DEBUG1 (("push "ID" on stack\n", f)) ; |
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| 90 | ASSERT (f >= 0 && f < nn) ; |
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| 91 | } |
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| 92 | ASSERT (Stack [h] == i) ; |
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| 93 | |
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| 94 | /* delete child list so that i gets ordered next time we see it */ |
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| 95 | Child [i] = EMPTY ; |
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| 96 | } |
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| 97 | else |
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| 98 | { |
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| 99 | /* the children of i (if there were any) are already ordered */ |
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| 100 | /* remove i from the stack and order it. Front i is kth front */ |
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| 101 | head-- ; |
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| 102 | AMD_DEBUG1 (("pop "ID" order "ID"\n", i, k)) ; |
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| 103 | Order [i] = k++ ; |
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| 104 | ASSERT (k <= nn) ; |
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| 105 | } |
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| 106 | |
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| 107 | #ifndef NDEBUG |
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| 108 | AMD_DEBUG1 (("\nStack:")) ; |
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| 109 | for (h = head ; h >= 0 ; h--) |
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| 110 | { |
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| 111 | Int j = Stack [h] ; |
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| 112 | AMD_DEBUG1 ((" "ID, j)) ; |
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| 113 | ASSERT (j >= 0 && j < nn) ; |
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| 114 | } |
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| 115 | AMD_DEBUG1 (("\n\n")) ; |
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| 116 | ASSERT (head < nn) ; |
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| 117 | #endif |
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| 118 | |
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| 119 | } |
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| 120 | return (k) ; |
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| 121 | } |
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