Global Trees

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Global Trees and Global Chunks are frameworks for supporting global view programming of irregular data structures on distributed memory machines. This framework allows the user to create, update, and access distributed tree structures in a global fashion, using one-sided operations for access. This system allows for parallel computations on these data structures in an asynchronous manner. Communication operations are automatically mapped to bulk data movement, allowing for efficient fine-grained access of tree data.

Both Global Trees (GT) and Global Chunks (GCL) use ARMCI and MPI internally. We have tested interoperability with MPI, ARMCI, and Global Arrays applications and are investigating interoperability with additional parallel programming tools.


Global Trees Programming Model

Global Trees provides a get/compute/put model for working with globally shared data. The user defines a data structure which contains a GT header structure for link/connectivity information (such as the child pointers) and then calls GT routines for manipulating these structures. Global pointers are dereferenced by get operations and updates are made with put operations. Scioto provides the user with a task pool programming model.

Below is pseudocode that shows the structure of a simple recursive GT tree copy operation.

void main(int *argc, char **argv) {
  gt_context_t *gtc = gt_init(&argc, &argv);
  gt_tree_t stree = my_create_a_tree(gtc, ...); // application-defined

  gt_tree_t dtree = gt_tree_create(gtc, ...);

  tree_copy(dtree, gt_get_root(stree), gt_get_root(dtree));

void tree_copy(gt_tree_t ng, gt_cnp_t *src, gt_cnp_t *dst) {
  gt_cnp_t *schild, *dchild;
  gt_node_t snode, dnode;
  int i;
  snode = gt_get_node(ng, src);
  dnode = gt_get_node(ng, dst);
  for (i=0;i<NUM_CHILDREN;i++) {
    schild = gt_get_child(ng, snode, i);
    if (gt_is_active(schild)) {
      dchild = gt_node_alloc(ng, dst);
      gt_link_child(ng, dst, dnode, i, dchild);
      tree_copy(ng, schild, dchild);
  gt_put_node(ng, dst, dnode);
  gt_finish_node(ng, snode);


Programming Interface

Documentation on Global Trees user API can be found here: GT API


Global Trees: A Framework for Linked Data Structures on Distributed Memory Parallel Systems"' PDF D. Brian Larkins, James Dinan, Sriram Krishnamoorthy, Atanas Rountev , P. Sadayappan Proc. 20th Intl. Conference on Supercomputing (SC). Austin, TX, Nov. 15-21, 2008.

Project Members


This research was supported in part by DOE grant #DE-FC02-06ER25755 and NSF grant #0403342.


We are currently providing early development snapshots for download. Please see the included README file for installation instructions. For questions or comments, contact Brian Larkins (blarkins at coastal dot edu).

  • Dev Release, 0.2 - July 2010 - [1]
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