From 46fe2af677c84137b4d127ce647140623275c96d Mon Sep 17 00:00:00 2001
From: Mikael Lund <Mlund@mac.com>
Date: Thu, 29 Jun 2023 15:13:22 +0200
Subject: [PATCH] Stop after max trials in electric potential calc.

Sampling in dense environments could cause an infinite
loop of no free space is found. This break after a certain
(hardcoded) number of attempts and gives a warning.
---
 src/analysis.cpp | 13 +++++++++++++
 src/analysis.h   |  1 +
 2 files changed, 14 insertions(+)

diff --git a/src/analysis.cpp b/src/analysis.cpp
index 4c0a75774..fa80b4627 100644
--- a/src/analysis.cpp
+++ b/src/analysis.cpp
@@ -2263,13 +2263,26 @@ void ElectricPotential::setPolicy(const json& j) {
         stride = j.at("stride").get<double>();
         output_information["stride"] = stride;
         applyPolicy = [&, stride] {
+            unsigned int cnt = 0;
             auto origin = targets.begin();
             do {
                 spc.geometry.randompos(origin->position, random);
+                cnt++;
+                if (cnt > max_overlap_trials) {
+                    faunus_logger->warn("{}: Max number of overlaps reached. Using overlapping point", name);
+                    break;
+                }
             } while (overlapWithParticles(origin->position));
+
+            cnt = 0;
             std::for_each(std::next(origin), targets.end(), [&](Target& target) {
                 do {
                     target.position = origin->position + stride * randomUnitVector(random);
+                    cnt++;
+                    if (cnt > max_overlap_trials) {
+                        faunus_logger->warn("{}: Max number of overlaps reached. Using overlapping point", name);
+                        break;
+                    }
                 } while (overlapWithParticles(target.position));
                 std::advance(origin, 1);
             });
diff --git a/src/analysis.h b/src/analysis.h
index 98c25cd6d..09f5ad1ef 100644
--- a/src/analysis.h
+++ b/src/analysis.h
@@ -228,6 +228,7 @@ class ElectricPotential : public Analysis {
     enum class Policies { FIXED, RANDOM_WALK, RANDOM_WALK_NO_OVERLAP, INVALID };
 
   private:
+    unsigned int max_overlap_trials = 100; //!< Maximum number of overlap checks before bailing out
     double histogram_resolution = 0.01; //!< Potential resolution
     unsigned int calculations_per_sample_event = 1;
     struct Target {