From 5a231fb7090464cd4e86db679bc41ea0ceddd13a Mon Sep 17 00:00:00 2001
From: Al <albarrentine@gmail.com>
Date: Tue, 6 Oct 2015 19:03:10 -0400
Subject: [PATCH] [graph] Builder for graphs not constructed in vertex-sorted
 order

---
 src/graph_builder.c | 108 ++++++++++++++++++++++++++++++++++++++++++++
 src/graph_builder.h |  53 ++++++++++++++++++++++
 2 files changed, 161 insertions(+)
 create mode 100644 src/graph_builder.c
 create mode 100644 src/graph_builder.h

diff --git a/src/graph_builder.c b/src/graph_builder.c
new file mode 100644
index 00000000..477044aa
--- /dev/null
+++ b/src/graph_builder.c
@@ -0,0 +1,108 @@
+#include "graph_builder.h"
+
+
+#define ks_lt_graph_edge(a, b) ((a).v1 < (b).v1)
+KSORT_INIT(graph_edge_array, graph_edge_t, ks_lt_graph_edge)
+
+#define ks_lt_graph_edge_sort_vertices(a, b) (((a).v1 < (b).v1) || ((a).v1 == (b).v1 && (a).v2 < (b).v2))
+KSORT_INIT(graph_edge_array_sort_vertices, graph_edge_t, ks_lt_graph_edge_sort_vertices)
+
+
+static void graph_builder_destroy(graph_builder_t *self) {
+    if (self == NULL) return;
+
+    if (self->edges != NULL) {
+        graph_edge_array_destroy(self->edges);
+    }
+
+    free(self);
+}
+
+graph_builder_t *graph_builder_new(graph_type_t type, bool fixed_rows) {
+    graph_builder_t *builder = malloc(sizeof(graph_builder_t));
+
+    builder->type = type;
+    builder->m = 0;
+    builder->n = 0;
+    builder->fixed_rows = fixed_rows;
+
+    builder->edges = graph_edge_array_new();
+    if (builder->edges == NULL) {
+        graph_builder_destroy(builder);
+        return NULL;
+    }
+
+    return builder;
+}
+
+
+static graph_t *graph_builder_build_edges(graph_builder_t *self, bool remove_duplicates) {
+    graph_t *graph = graph_new(self->type);
+    if (graph == NULL) return NULL;
+
+    uint32_t last_vertex = 0;
+    uint32_t last_edge = 0;
+
+    for (int i = 0; i < self->edges->n; i++) {
+        graph_edge_t edge = self->edges->a[i];
+        if (edge.v1 > last_vertex) {
+            for (uint32_t row = last_vertex; row < edge.v1; row++) {
+                graph_finalize_vertex(graph);
+
+            }
+
+        }
+
+        if (!remove_duplicates || i == 0 || edge.v1 != last_vertex || edge.v2 != last_edge) {
+            graph_append_edge(graph, edge.v2);
+        }
+        last_vertex = edge.v1;
+        last_edge = edge.v2;
+    }
+
+    graph_finalize_vertex(graph);
+
+    return graph;
+}
+
+graph_t *graph_builder_finalize(graph_builder_t *self, bool sort_edges, bool remove_duplicates) {
+    graph_t *graph;
+    if (remove_duplicates && !sort_edges) {
+        sort_edges = true;
+    }
+
+    if (!sort_edges) {
+        ks_introsort(graph_edge_array, self->edges->n, self->edges->a);
+        graph = graph_builder_build_edges(self, remove_duplicates);
+    } else {
+        ks_introsort(graph_edge_array_sort_vertices, self->edges->n, self->edges->a);
+        graph = graph_builder_build_edges(self, remove_duplicates);
+    }
+
+    graph->fixed_rows = self->fixed_rows;
+    graph_set_size(graph);
+
+    graph_builder_destroy(self);
+    return graph;
+}
+
+void graph_builder_add_edge(graph_builder_t *self, uint32_t v1, uint32_t v2) {
+    if (v1 == v2) return;
+    graph_edge_t edge;
+
+    if (self->type != GRAPH_UNDIRECTED || v2 > v1) {
+        edge = (graph_edge_t) {v1, v2};
+    } else {
+        edge = (graph_edge_t) {v2, v1};
+    }
+
+    graph_edge_array_push(self->edges, edge);
+
+    if (v1 >= self->m) {
+        self->m = v1 + 1;
+    }
+
+    if (v2 >= self->n) {
+        self->n = v2 + 1;
+    }
+}
diff --git a/src/graph_builder.h b/src/graph_builder.h
new file mode 100644
index 00000000..897ee372
--- /dev/null
+++ b/src/graph_builder.h
@@ -0,0 +1,53 @@
+/*
+graph_builder.h
+---------------
+
+For graphs it's sometimes impractical to assume that the vertices
+will arrive in sorted order, which is required for constructing a
+compressed sparse row (CSR) matrix. This is simply a coordinate matrix
+(COO) style constructor where the rows/columns do not need to be
+ordered or unique.
+
+*/
+
+#ifndef GRAPH_BUILDER_H
+#define GRAPH_BUILDER_H
+
+#include "collections.h"
+#include "file_utils.h"
+#include "graph.h"
+
+
+typedef struct graph_edge {
+    uint32_t v1;
+    uint32_t v2;
+} graph_edge_t;
+
+VECTOR_INIT(graph_edge_array, graph_edge_t)
+
+
+typedef struct graph_builder {
+    graph_type_t type;
+    size_t m;
+    size_t n;
+    bool fixed_rows;
+    graph_edge_array *edges;
+} graph_builder_t;
+
+graph_builder_t *graph_builder_new(graph_type_t type, bool fixed_rows);
+/*
+Destroy the builder and return a graph.
+
+Note: remove_duplicates=true requires sorting the indices. Can only preserve
+edge ordering if we can guarantee there are no duplicates.
+*/
+graph_t *graph_builder_finalize(graph_builder_t *self, bool sort_edges, bool remove_duplicates);
+
+/*
+Add an edge. Order 
+
+Reflexive edges not allowed.
+*/
+void graph_builder_add_edge(graph_builder_t *self, uint32_t v1, uint32_t v2);
+
+#endif
\ No newline at end of file