From 629989f1967306246b6a2559ac16c60fabaae713 Mon Sep 17 00:00:00 2001
From: Joshua Coles <josh@coles.to>
Date: Wed, 1 Mar 2023 21:32:35 +0000
Subject: [PATCH] Add stickProbability

---
 DLASystem.cpp | 25 +++++++++----------------
 DLASystem.h   |  7 ++++++-
 mainDLA.cpp   |  9 +++++----
 3 files changed, 20 insertions(+), 21 deletions(-)

diff --git a/DLASystem.cpp b/DLASystem.cpp
index e006c10..f2b6f87 100644
--- a/DLASystem.cpp
+++ b/DLASystem.cpp
@@ -163,9 +163,7 @@ void DLASystem::moveLastParticle() {
         particleList.pop_back();  // remove particle from particleList
         numParticles--;
         setParticleInactive();
-    }
-        // check if destination is empty
-    else if (readGrid(newpos) == 0) {
+    } else if (readGrid(newpos) == 0) {
         setGrid(lastP->pos, 0);  // set the old grid site to empty
         // update the position
         particleList[numParticles - 1]->pos[0] = newpos[0];
@@ -178,37 +176,32 @@ void DLASystem::moveLastParticle() {
             setParticleInactive();  // make the particle inactive (stuck)
             updateClusterRadius(lastP->pos);  // update the cluster radius, addCircle, etc.
         }
-    } else {
-        // if we get to here then we are trying to move to an occupied site
-        // (this should never happen as long as the sticking probability is 1.0)
-        cerr << "reject " << rr << endl;
-        cerr << lastP->pos[0] << " " << lastP->pos[1] << endl;
-        //cerr << newpos[0] << " " << newpos[1] << " " << (int)newpos[0] << endl;
-        //printOccupied();
     }
 }
 
 // check if the last particle should stick (to a neighbour)
 int DLASystem::checkStick() {
     Particle *lastP = particleList[numParticles - 1];
-    int result = 0;
     // loop over neighbours
     for (int i = 0; i < 4; i++) {
         double checkpos[2];
         setPosNeighbour(checkpos, lastP->pos, i);
-        // if the neighbour is occupied...
-        if (readGrid(checkpos) == 1)
-            result = 1;
+        // if the neighbour is occupied and the particle will stick probabilistically.
+        if (readGrid(checkpos) == 1 && rgen.random01() < stickProbability) {
+            return 1;
+        }
     }
-    return result;
+
+    return 0;
 }
 
 
 // constructor
-DLASystem::DLASystem(int maxParticles, string csvPath) {
+DLASystem::DLASystem(const int maxParticles, const string &csvPath, const double stickProbability) {
     cerr << "creating system, gridSize " << gridSize << endl;
     numParticles = 0;
     endNum = maxParticles;
+    this->stickProbability = stickProbability;
 
     // allocate memory for the grid, remember to free the memory in destructor
     grid = new int *[gridSize];
diff --git a/DLASystem.h b/DLASystem.h
index b305c92..b543e59 100644
--- a/DLASystem.h
+++ b/DLASystem.h
@@ -24,6 +24,11 @@ class DLASystem {
     vector<Particle*> particleList;
     int numParticles;
 
+    /*
+     * The probability that a particle will stick at a given site when adjacent.
+     * */
+    double stickProbability;
+
     // delete particles and clear the particle list
     void clearParticles();
 
@@ -66,7 +71,7 @@ class DLASystem {
     int lastParticleIsActive;
   
     // constructor
-    explicit DLASystem(int maxParticles, string csvPath);
+    explicit DLASystem(int maxParticles, const string &csvPath, double stickProbability);
     // destructor
     ~DLASystem();
   
diff --git a/mainDLA.cpp b/mainDLA.cpp
index 0e427be..8f387e3 100644
--- a/mainDLA.cpp
+++ b/mainDLA.cpp
@@ -3,18 +3,19 @@
 #include "DLASystem.h"
 
 int main(int argc, char **argv) {
-    if (argc != 4) {
-        cerr << "Usage " << argv[0] << " <seed> <maxParticles> <csvPath>" << endl;
+    if (argc != 5) {
+        cerr << "Usage " << argv[0] << " <seed> <maxParticles> <stickProbability> <csvPath>" << endl;
         return 1;
     }
 
     int seed = std::stoi(argv[1]);
     int maxParticles = std::stoi(argv[2]);
-    string csvPath = argv[3];
+    double stickProbability = std::stod(argv[3]);
+    string csvPath = argv[4];
     std::cerr << "Setting seed " << seed << endl;
 
     // create the system
-    auto *sys = new DLASystem(maxParticles,  csvPath);
+    auto *sys = new DLASystem(maxParticles, csvPath, stickProbability);
     sys->setSeed(seed);
     sys->running = true;