Question about collision calculation time

[Linjackffy]

Hello！
I have noticed that the calculated time increases as the distance between objects decreases.
Is this expected behavior, or is there a mistake in my parameter settings.
Could someone help answer this question?
Below is the code I am using.

The UR model is download from https://github.com/stack-of-tasks/pinocchio/tree/master/models
And you need to replace ur5.srdf with this file:

<?xml version="1.0"?>
<!--

   UR-5 SRDF

   This file is an alternative way of specifying semantics on the robot
   structure.

   It also provides:
   - the set of interesting collision pairs

  -->
<robot name="ur5">
  <disable_collisions link1="base_link" link2="shoulder_link"/>
  <disable_collisions link1="base_link" link2="upper_arm_link"/>
  <disable_collisions link1="shoulder_link" link2="upper_arm_link"/>
  <disable_collisions link1="upper_arm_link" link2="forearm_link"/>
  <disable_collisions link1="forearm_link" link2="wrist_1_link"/>
  <disable_collisions link1="forearm_link" link2="wrist_2_link"/>
  <disable_collisions link1="forearm_link" link2="wrist_3_link"/>
  <disable_collisions link1="wrist_1_link" link2="wrist_2_link"/>
  <disable_collisions link1="wrist_1_link" link2="wrist_3_link"/>
  <disable_collisions link1="wrist_2_link" link2="wrist_3_link"/>
  <disable_collisions link1="ee_link" link2="base_link"/>
  <disable_collisions link1="ee_link" link2="shoulder_link"/>
  <disable_collisions link1="ee_link" link2="upper_arm_link"/>
  <disable_collisions link1="ee_link" link2="forearm_link"/>
  <disable_collisions link1="ee_link" link2="wrist_1_link"/>
  <disable_collisions link1="ee_link" link2="wrist_2_link"/>
  <disable_collisions link1="ee_link" link2="wrist_3_link"/>
</robot>

#include "pinocchio/parsers/urdf.hpp"
#include "pinocchio/parsers/srdf.hpp"

#include "pinocchio/algorithm/joint-configuration.hpp"
#include "pinocchio/algorithm/geometry.hpp"
#include "pinocchio/collision/collision.hpp"

#include <iostream>

// PINOCCHIO_MODEL_DIR is defined by the CMake but you can define your own modeldirectory here.
#ifndef PINOCCHIO_MODEL_DIR
  #define PINOCCHIO_MODEL_DIR "path_to_the_model_dir"
#endif

int main(int /*argc*/, char ** /*argv*/)
{
  using namespace pinocchio;
  const std::string robots_model_path = PINOCCHIO_MODEL_DIR;

  // You should change here to set up your own URDF file
  const std::string urdf_filename =
    robots_model_path
    + std::string("/example-robot-data/robots/ur_description/urdf/ur5_robot.urdf");
  // You should change here to set up your own SRDF file
  const std::string srdf_filename =
    robots_model_path + std::string("/example-robot-data/robots/ur_description/srdf/ur5.srdf");

  // Load the URDF model contained in urdf_filename
  Model model;
  pinocchio::urdf::buildModel(urdf_filename, model);

  // Build the data associated to the model
  Data data(model);

  // Load the geometries associated to model which are contained in the URDF file
  GeometryModel geom_model;
  pinocchio::urdf::buildGeom(
    model, urdf_filename, pinocchio::COLLISION, geom_model, robots_model_path);

  // Add all possible collision pairs and remove the ones collected in the SRDF file
  geom_model.addAllCollisionPairs();
  pinocchio::srdf::removeCollisionPairs(model, geom_model, srdf_filename);
  
  // Build the data associated to the geom_model
  GeometryData geom_data(geom_model); // contained the intermediate computations, like the placement
                                      // of all the geometries with respect to the world frame

  for (size_t k = 0; k < geom_model.collisionPairs.size(); ++k) {
    geom_data.collisionRequests[k].security_margin = 0.003;
    geom_data.collisionRequests[k].num_max_contacts = 1;
    geom_data.collisionRequests[k].enable_contact = false;
    geom_data.collisionRequests[k].enable_distance_lower_bound = false;
  }

  Eigen::VectorXd q(model.nq);
  q << 0,0,-135,180,90,0;
  q *= M_PI / 180;

  for (size_t i = 0; i < 100; i++) {
    q[2] -= 0.2 * M_PI / (100 - 1);
    std::chrono::time_point<std::chrono::high_resolution_clock> start = std::chrono::high_resolution_clock::now();
    bool ret = computeCollisions(model, data, geom_model, geom_data, q, true);
    auto stop = std::chrono::high_resolution_clock::now();
    double time = std::chrono::duration_cast<std::chrono::nanoseconds>(stop - start).count() / 1000.0; // [µs]
    std::size_t min_idx = computeDistances(geom_model, geom_data);
    const hpp::fcl::DistanceResult & dr = geom_data.distanceResults[geom_model.collisionPairs.size() - 1];
    std::cout << "min dis " << dr.min_distance << " calc time : " << time;

    if (ret) {
        auto k = geom_data.collisionPairIndex;
        const CollisionPair &cp = geom_model.collisionPairs[k];
        std::cout << " axis " << cp.first << " axis " << cp.second << " collision" << std::endl;
        const hpp::fcl::CollisionResult & cr = geom_data.collisionResults[k];

        // if (cr.numContacts() > 0) {
        //   for (auto &c : cr.getContacts()) {
        //     std::cout << "contact point " << c.pos.transpose() << std::endl;
        //   }
        // }
    } else {
        std::cout << std::endl;
    }
  }

  return 0;
}

Here is the output:

min dis 0.0799548 calc time : 52.969
min dis 0.0777391 calc time : 14.056
min dis 0.0755248 calc time : 11.606
min dis 0.073312 calc time : 19.186
min dis 0.071101 calc time : 16.128
min dis 0.0688921 calc time : 14.519
min dis 0.0666855 calc time : 13.988
min dis 0.0644817 calc time : 16.037
min dis 0.0622809 calc time : 13.911
min dis 0.0600836 calc time : 16.362
min dis 0.0578904 calc time : 20.941
min dis 0.0557017 calc time : 13.269
min dis 0.0535182 calc time : 18.057
min dis 0.0513407 calc time : 29.612
min dis 0.0491702 calc time : 21.643
min dis 0.0470075 calc time : 18.708
min dis 0.044854 calc time : 16.54
min dis 0.0426585 calc time : 12.781
min dis 0.0404537 calc time : 45.242
min dis 0.0382486 calc time : 17.574
min dis 0.0360434 calc time : 32.419
min dis 0.0338381 calc time : 17.544
min dis 0.0316359 calc time : 13.488
min dis 0.02944 calc time : 25.817
min dis 0.0272518 calc time : 19.822
min dis 0.0250736 calc time : 232.99
min dis 0.0229084 calc time : 15.769
min dis 0.0207601 calc time : 50.033
min dis 0.0186346 calc time : 27.923
min dis 0.0165409 calc time : 30.177
min dis 0.0144908 calc time : 28.793
min dis 0.0124547 calc time : 41.515
min dis 0.0104179 calc time : 135.268
min dis 0.00838033 calc time : 163.621
min dis 0.00634214 calc time : 220.214
min dis 0.00430341 calc time : 408.062
min dis 0.00226422 calc time : 166.596 axis 2 axis 6 collision
min dis 0.00022464 calc time : 67.519 axis 2 axis 6 collision
min dis 0 calc time : 81.219 axis 2 axis 6 collision
min dis 0 calc time : 103.116 axis 2 axis 6 collision
min dis 0 calc time : 159.164 axis 2 axis 6 collision
min dis 0 calc time : 69.447 axis 2 axis 5 collision
min dis 0 calc time : 61.47 axis 2 axis 5 collision
min dis 0 calc time : 146.14 axis 2 axis 5 collision
min dis 0 calc time : 79.252 axis 2 axis 5 collision
min dis 0 calc time : 77.531 axis 2 axis 5 collision
min dis 0 calc time : 644.931 axis 2 axis 5 collision
min dis 0 calc time : 160.951 axis 2 axis 5 collision
min dis 0 calc time : 203.695 axis 2 axis 5 collision
min dis 0 calc time : 138.126 axis 2 axis 5 collision
min dis 0 calc time : 676.629 axis 2 axis 5 collision
min dis 0 calc time : 413.353 axis 2 axis 5 collision
min dis 0 calc time : 174.798 axis 2 axis 5 collision
min dis 0 calc time : 161.452 axis 2 axis 5 collision
min dis 0 calc time : 185.219 axis 2 axis 5 collision
min dis 0 calc time : 500.083 axis 2 axis 5 collision
min dis 0 calc time : 331.636 axis 2 axis 5 collision
min dis 0 calc time : 668.264 axis 2 axis 5 collision
min dis 0 calc time : 446.05 axis 2 axis 5 collision
min dis 0 calc time : 710.832 axis 2 axis 5 collision
min dis 0 calc time : 823.992 axis 1 axis 5 collision
min dis 0 calc time : 177.972 axis 1 axis 5 collision
min dis 0 calc time : 526.987 axis 1 axis 5 collision
min dis 0 calc time : 171.913 axis 1 axis 5 collision
min dis 0 calc time : 167.472 axis 1 axis 5 collision
min dis 0 calc time : 65.931 axis 1 axis 5 collision
min dis 0 calc time : 57.89 axis 1 axis 5 collision
min dis 0 calc time : 71.202 axis 1 axis 5 collision
min dis 0 calc time : 148.807 axis 1 axis 5 collision
min dis 0 calc time : 70.804 axis 1 axis 5 collision
min dis 0 calc time : 72.497 axis 1 axis 5 collision
min dis 0 calc time : 84.643 axis 1 axis 5 collision
min dis 0 calc time : 145.48 axis 1 axis 5 collision
min dis 0 calc time : 172.607 axis 1 axis 5 collision
min dis 0 calc time : 492.076 axis 1 axis 5 collision
min dis 0 calc time : 189.492 axis 1 axis 5 collision
min dis 0 calc time : 381.186 axis 1 axis 5 collision
min dis 0 calc time : 244.56 axis 1 axis 5 collision
min dis 0 calc time : 793.912 axis 1 axis 5 collision
min dis 0 calc time : 1253.15 axis 1 axis 5 collision
min dis 0 calc time : 188.201 axis 1 axis 3 collision
min dis 0 calc time : 431.315 axis 1 axis 3 collision
min dis 0 calc time : 188.977 axis 1 axis 3 collision
min dis 0 calc time : 175.32 axis 1 axis 3 collision
min dis 0 calc time : 761.087 axis 1 axis 3 collision
min dis 0 calc time : 188.233 axis 1 axis 3 collision
min dis 0 calc time : 344.052 axis 1 axis 3 collision
min dis 0 calc time : 322.679 axis 1 axis 3 collision
min dis 0 calc time : 301.51 axis 1 axis 3 collision
min dis 0 calc time : 392.077 axis 1 axis 3 collision
min dis 0 calc time : 97.263 axis 1 axis 3 collision
min dis 0 calc time : 1190.55 axis 1 axis 3 collision
min dis 0 calc time : 214.961 axis 1 axis 3 collision
min dis 0 calc time : 126.906 axis 1 axis 3 collision
min dis 0 calc time : 80.022 axis 1 axis 3 collision
min dis 0 calc time : 53.382 axis 1 axis 3 collision
min dis 0 calc time : 39.093 axis 1 axis 3 collision
min dis 0 calc time : 49.896 axis 1 axis 3 collision
min dis 0 calc time : 52.244 axis 1 axis 3 collision
min dis 0 calc time : 62.919 axis 1 axis 3 collision