[dpdk-dev] [PATCH v4 05/29] graph: implement internal graph operation helpers

Andrzej Ostruszka amo at semihalf.com
Tue Apr 7 14:54:51 CEST 2020


On 4/7/20 2:27 PM, Jerin Jacob wrote:
> On Tue, Apr 7, 2020 at 5:46 PM Andrzej Ostruszka <amo at semihalf.com> wrote:
> 
>>> +int
>>> +graph_bfs(struct graph *graph, struct graph_node *start)
>>> +{
>>> +     struct graph_node **queue, *v, *tmp;
>>> +     uint16_t head = 0, tail = 0;
>>> +     rte_edge_t i;
>>> +     size_t sz;
>>> +
>>> +     sz = sizeof(struct graph_node *) * graph_nodes_count(graph);
>>> +     queue = malloc(sz);
>>> +     if (queue == NULL)
>>> +             SET_ERR_JMP(ENOMEM, fail, "Failed to alloc BFS queue of %zu",
>>> +                         sz);
>>> +
>>> +     /* BFS algorithm */
>>> +     queue[tail++] = start;
>>> +     start->visited = true;
>>> +     while (head != tail) {
>>> +             v = queue[head++];
>>> +             for (i = 0; i < v->node->nb_edges; i++) {
>>> +                     tmp = v->adjacency_list[i];
>>> +                     if (tmp->visited == false) {
>>> +                             queue[tail++] = tmp;
>>> +                             tmp->visited = true;
>>> +                     }
>>> +             }
>>> +     }
>>> +
>>> +     free(queue);
>>> +     return 0;
>>> +
>>> +fail:
>>> +     return -rte_errno;
>>> +}
>>
>> What is the purpose of this function?  It looks like just marking as
>> visited.  Then maybe change the name to graph_mark_bfs() or something
>> like that.
> 
> graph_ops.c has all generic graph-related functions.
> BFS(Breadth-First Search) is a generic graph operation. The primitive
> can be used for various other graph operations.
> IMO, It is better to avoid connecting with a marking using case in the
> function name.
> 
> 
>>
>>> +
>>> +/* Check whether a node has connected path or parent node */
>>> +int
>>> +graph_has_isolated_node(struct graph *graph)
>>> +{
>>> +     struct graph_node *graph_node;
>>> +
>>> +     graph_mark_nodes_as_not_visited(graph);
> 
> See below,
> 
>>> +
>>> +     STAILQ_FOREACH(graph_node, &graph->node_list, next) {
>>> +             if (graph_node->node->flags & RTE_NODE_SOURCE_F) {
>>> +                     if (graph_node->node->nb_edges == 0)
>>> +                             SET_ERR_JMP(EINVAL, fail,
>>> +                                         "%s node needs minimum one edge",
>>> +                                         graph_node->node->name);
>>> +                     if (graph_bfs(graph, graph_node))
>>> +                             goto fail;
>>> +             }
>>> +     }
>>> +
>>> +     STAILQ_FOREACH(graph_node, &graph->node_list, next)
>>> +             if (graph_node->visited == false)
>>> +                     SET_ERR_JMP(EINVAL, fail, "Found isolated node %s",
>>> +                                 graph_node->node->name);> +
>>> +     return 0;
>>
>> You don't want to clear visited because it will not be used or cleared
>> on next call?
> 
> See above graph_mark_nodes_as_not_visited() function.

Yes I noticed that and referred to it in the question.  My intention was
to ask whether you are fine with graph having visited=true for the rest
of its life, or should we clear them again at the end of this function.

With regards
Andrzej Ostruszka


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