232 lines
6.2 KiB
C++
232 lines
6.2 KiB
C++
#include "iostream"
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#include "cmath"
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#include "vector"
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using namespace std;
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struct point_2d
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{
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double x, y;
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};
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struct source : point_2d
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{
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double rad;
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double slow;
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};
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struct grid_point : point_2d
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{
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int tag = 0; //0 = far away, 1 = close, 2 = active
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double time = 1e+30;
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double syn_time = 1e+30; //synthetic direct arrive time (only for error test)
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double slow;
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grid_point* neighbor[4] = {NULL,NULL,NULL,NULL}; //up down left right
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};
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typedef vector<grid_point> grid_point_array;
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typedef vector<grid_point*> ptr_grid_point_array;
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void update_heap(ptr_grid_point_array& a, int i, int n)
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{
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int iMax = i,
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iLeft = 2 * i + 1,
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iRight = 2 * (i + 1);
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if (iLeft < n && a[iMax]->time < a[iLeft]->time) {
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iMax = iLeft;
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}
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if (iRight < n && a[iMax]->time < a[iRight]->time) {
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iMax = iRight;
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}
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if (iMax != i) {
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grid_point* tmp = a[iMax];
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a[iMax] = a[i];
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a[i] = tmp;
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update_heap(a, iMax, n);
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}
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return;
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}
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void heap_sort(ptr_grid_point_array& a, int n)
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{
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for (int i = (n - 1) / 2; i >= 0; i--) {
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update_heap(a, i, n);
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}
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for (int i = n - 1; i > 0; --i) {
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grid_point* tmp = a[i];
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a[i] = a[0];
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a[0] = tmp;
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update_heap(a, 0, i);
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}
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return;
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}
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double dis_point_2d(point_2d a, point_2d b)
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{
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return sqrt((a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y));
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}
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void local_update(grid_point* point_ptr, double delta_h)
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{
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//solve a quadratic equation to get the trial time
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/*
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double a = 0, b = 0, c = -1.0 * pow(delta_h,2) * pow(point_ptr->slow,2);
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for (int i = 0; i < 4; i++)
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{
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if (point_ptr->neighbor[i] != NULL && point_ptr->neighbor[i]->tag == 2)
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{
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a += 1.0;
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b += -2.0*point_ptr->neighbor[i]->time;
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c += pow(point_ptr->neighbor[i]->time,2);
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}
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}
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*/
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// a second order upwind difference scheme
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double a = 0, b = 0, c = -4.0 * pow(delta_h,2) * pow(point_ptr->slow,2);
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for (int i = 0; i < 4; i++)
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{
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if (point_ptr->neighbor[i] != NULL && point_ptr->neighbor[i]->tag == 2)
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{
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a += 4.0;
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b += -8.0*point_ptr->neighbor[i]->time;
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c += 4.0*pow(point_ptr->neighbor[i]->time,2);
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if (point_ptr->neighbor[i]->neighbor[i] != NULL && point_ptr->neighbor[i]->neighbor[i]->tag == 2)
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{
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a += 5.0;
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b += -16.0*point_ptr->neighbor[i]->time + 6.0*point_ptr->neighbor[i]->neighbor[i]->time;
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c += 12.0*pow(point_ptr->neighbor[i]->time,2) - 8.0*point_ptr->neighbor[i]->time*point_ptr->neighbor[i]->neighbor[i]->time
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+ pow(point_ptr->neighbor[i]->neighbor[i]->time,2);
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}
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}
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}
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double delta = b*b - 4.0*a*c; //in a upwind scheme, delta is always bigger than zero
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point_ptr->time = min(point_ptr->time, 0.5*(sqrt(delta) - b)/a);
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return;
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}
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void abnormal_slowness(grid_point_array& grid_recall, double ab_slow,double xmin, double xmax, double ymin, double ymax)
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{
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for (int i = 0; i < grid_recall.size(); i++)
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{
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if (grid_recall[i].x >= xmin && grid_recall[i].x <= xmax && grid_recall[i].y >= ymin && grid_recall[i].y <= ymax)
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{
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grid_recall[i].slow = ab_slow;
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}
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}
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return;
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}
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int main(int argc, char const *argv[])
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{
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//set grid parameters
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int xnum = 201;
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int ynum = 101;
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double xmin = 0;
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double ymin = 0;
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double dh = 5;
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//set source parameters
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source init_source;
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init_source.x = 50;
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init_source.y = 250;
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init_source.rad = 25;
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init_source.slow = 1.0;
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//initialize grid
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grid_point_array grid_2d;
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grid_2d.resize(xnum*ynum);
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//down-left corner to up-right corner
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for (int i = 0; i < ynum; i++)
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{
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for (int j = 0; j < xnum; j++)
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{
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grid_2d[i*xnum+j].x = xmin + dh*j;
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grid_2d[i*xnum+j].y = ymin + dh*i;
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grid_2d[i*xnum+j].slow = init_source.slow;
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if (i <= ynum-2) grid_2d[i*xnum+j].neighbor[0] = &grid_2d[(i+1)*xnum+j]; //up
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if (i >= 1) grid_2d[i*xnum+j].neighbor[1] = &grid_2d[(i-1)*xnum+j]; //down
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if (j >= 1) grid_2d[i*xnum+j].neighbor[2] = &grid_2d[i*xnum+j-1]; //left
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if (j <= xnum-2) grid_2d[i*xnum+j].neighbor[3] = &grid_2d[i*xnum+j+1]; //right
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//calculate synthetic direct arrive time
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grid_2d[i*xnum+j].syn_time = dis_point_2d(grid_2d[i*xnum+j], init_source) * init_source.slow;
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}
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}
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//add abnormal slowness here
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//abnormal_slowness(grid_2d,2.0,250,500,0,500);
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//abnormal_slowness(grid_2d,4.0,800,1000,0,500);
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//abnormal_slowness(grid_2d,1e+30,200,250,0,250);
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//abnormal_slowness(grid_2d,1e+30,500,550,250,500);
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//abnormal_slowness(grid_2d,1e+30,800,850,0,250);
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ptr_grid_point_array close_node_ptr;
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//initialize source nodes and close nodes;
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for (int i = 0; i < xnum*ynum; i++)
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{
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if (dis_point_2d(grid_2d[i],init_source) <= init_source.rad)
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{
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grid_2d[i].tag = 2;
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grid_2d[i].time = dis_point_2d(grid_2d[i],init_source) * init_source.slow;
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}
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}
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for (int i = 0; i < xnum*ynum; i++)
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{
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if (grid_2d[i].tag == 2)
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{
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for (int j = 0; j < 4; j++)
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{
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if (grid_2d[i].neighbor[j] != NULL && grid_2d[i].neighbor[j]->tag == 0)
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{
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grid_2d[i].neighbor[j]->tag = 1;
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close_node_ptr.push_back(grid_2d[i].neighbor[j]);
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}
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}
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}
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}
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//calculate trial time for all close nodes
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for (int i = 0; i < close_node_ptr.size(); i++)
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{
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local_update(close_node_ptr[i], dh);
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}
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//marching forward and updating the close nodes set
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while (!close_node_ptr.empty())
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{
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// heap sort close nodes pointers to put the node first that has smallest time
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heap_sort(close_node_ptr,close_node_ptr.size());
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//change the first node's tag to 2 and update it's neighbor's time if it is not active
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close_node_ptr[0]->tag = 2;
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for (int i = 0; i < 4; i++)
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{
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if (close_node_ptr[0]->neighbor[i] != NULL && close_node_ptr[0]->neighbor[i]->tag == 0)
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{
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close_node_ptr[0]->neighbor[i]->tag = 1;
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local_update(close_node_ptr[0]->neighbor[i], dh);
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close_node_ptr.push_back(close_node_ptr[0]->neighbor[i]);
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}
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else if (close_node_ptr[0]->neighbor[i] != NULL && close_node_ptr[0]->neighbor[i]->tag == 1)
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{
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local_update(close_node_ptr[0]->neighbor[i], dh);
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}
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}
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close_node_ptr.erase(close_node_ptr.begin());
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}
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for (int i = 0; i < xnum*ynum; i++)
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{
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if (grid_2d[i].time > 1e+10)
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{
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cout << grid_2d[i].x << " " << grid_2d[i].y << " " << grid_2d[i].tag << " " << grid_2d[i].syn_time << " nan " << grid_2d[i].time - grid_2d[i].syn_time << endl;
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}
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else cout << grid_2d[i].x << " " << grid_2d[i].y << " " << grid_2d[i].tag << " " << grid_2d[i].syn_time << " " << grid_2d[i].time << " " << grid_2d[i].time - grid_2d[i].syn_time << endl;
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}
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return 0;
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} |