Parallel Programming - Final version

[matches/honours.git] / course / semester2 / pprog / assignment1 / nbody-bh / tree.h

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+/**
+ * @file tree.h
+ * @purpose Declaration of tree structures for Barnes Hut clustering algorithm for N-Body simulator
+ * @author Sam Moore (20503628) - 2012
+ */
+
+#ifndef _TREE_H
+#define _TREE_H
+
+#include "nbody.h"
+
+#define SUB_DIVISIONS 8
+
+// Define to break everything and nest the threading
+// (Program becomes impossibly slow, but feel free to try)
+// #define USE_THREADS
+
+/**
+ * Structure to represent each node of the tree (a cube (actually a prism) in space)
+ *     I call them.... "Data Prisms"
+ *     But that takes too long to type, so they are Node instead
+ */
+typedef struct n 
+{
+       float x[DIMENSIONS]; // The corner of the cube with smallest valued co-ordinates
+       float size[DIMENSIONS]; // The lengths of the cube faces.
+
+       Body * * body; // Array of pointers to bodies in the node; dynamically created
+       unsigned N; // Number of bodies in the node; valid length of array
+       unsigned allocated; //space allocated for bodies; used to dynamically resize array (doubles every time array is filled).
+
+       float mass;
+       float com[DIMENSIONS]; // Centre of Mass
+
+       struct n * children[SUB_DIVISIONS]; // children nodes (smaller data prisms)
+       struct n * parent; // parent node; the bodies in this node are also in the parent node (bigger data prism)
+
+       
+} Node;
+
+void Node_SetSpace(Node * node, float x[DIMENSIONS], float size[DIMENSIONS]); //set the position and volume of a Node
+void Node_Destroy(Node * node); // Cleanup a Node
+unsigned Node_FindBodies(Node * n, System * s); // Find all bodies in System s contained in Node n
+unsigned Node_Subdivide(Node * node, System * s); // Divide Node n into smaller nodes until each node has 1 Body in it
+
+float Node_CalculateMass(Node * node); // Calculate the total mass of a Node
+
+unsigned Node_AddBody(Node * n, Body * b); // Add a body to a Node
+
+unsigned Generate_Tree(System * s, Node * n); // Generate the tree of Nodes for the *first* time
+
+unsigned Update_Tree(System * s, Node * n); // Subsequently update the tree
+
+unsigned Node_Forces(Body * b, Node * node, float theta); // Calculate forces on body due to node. Theta is the approximation factor.
+
+void Node_FitSystem(Node * n, System * s); // Take a node and increase the size until it contains the entire system.
+
+
+Node * Node_Create(Node * parent); // Construct a node for the first time
+
+bool Node_ContainsBody(Node * n, Body * b); // Check if a Body is in a Node
+Body * Node_Body(Node * n, unsigned index); // Identify the n'th body in a Node. Required because the Body* array is slightly special.
+void Draw_Node(Node * n); // Draw a cube corresponding to Node n
+
+
+// Used if nested threading is desired; not recommended. Breaks things
+#ifdef USE_THREADS
+void Prepare_Threads(unsigned max); // Attempt to create "max" threads on the next #pragma omp parallel
+extern unsigned nested_used; // Number of nested threads created
+extern omp_lock_t nested_lock; // Lock around nested_used
+#endif //USE_THREADS
+
+
+#endif //_TREE_H
+
+//EOF