sorting vectors based on size()

sorting vectors based on size()

By : pwelo
Date : October 16 2020, 11:12 AM
it fixes the issue i have a 2-d vector like vector < vector < coordinates > > v( points); where coordinates class is: , 1) make a function that compares two vectors based on size:
code :

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Sorting vectors based on length in C

Sorting vectors based on length in C

By : Strong Lei
Date : March 29 2020, 07:55 AM
will be helpful for those in need I want to make a programm that takes the dimension and numbers of vectors to be sorted based on their length. Most of the code works but the sort part of the program doesnt. Basically what I want to do there is: compare the output from the bereken_lengte function from 2 places in the array w. But nothing seems to happen. Also in the function bereken_lengte, I cant take the roots of the sum after the loop ended.
code :
double bereken_lengte(double *array, int dim)
  unsigned int i;
  double sum =0.0;
  for(i=0; i<dim; ++i)
    sum += pow(array[i],2);
  return sum;
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

double bereken_lengte(double *array, size_t dim)
  size_t i;
  double sum=0.0;
  for(i=0; i<dim; ++i)
    sum += pow(array[i],2);
  return sum;

        /* this is ugly: qsort only allows only two arguments */
static size_t ze_third_argument=0;
int srt_pdbl(void *l, void *r)
double **dl = l, **dr = r;
double diff;
diff = bereken_lengte( *dl, ze_third_argument) - bereken_lengte( *dr, ze_third_argument) ;
return (int) diff;

void sort_vector(double *w[] , size_t num , size_t dik )
ze_third_argument = dik;
qsort(w, num, sizeof *w, srt_pdbl );

int main (void)
  size_t dim, num;
  size_t i, j,k,l;
  double **w;
  scanf ("%zu %zu", &dim, &num);          /* read N and M */
  w = calloc (num, sizeof *w);  /* allocate array of M pointers */
  for (i = 0; i < num; i++)
    /* allocate space for N dimensional vector */
    w[i] = calloc (dim, sizeof *w[i] );
    /* read the vector */
    for (j = 0; j < dim; j++)
      scanf ("%lf", &w[i][j]);
  for(k=0; k<num; ++k)
    for(l=0; l<dim; ++l)
      printf("%f ", w[k][l]);
  return 0;
Sorting Vectors based on their correlation

Sorting Vectors based on their correlation

By : William John-Pierre
Date : March 29 2020, 07:55 AM
will help you Pearsons will work. So will the usual dot product, Manhattan, etc.
You realize, of course, that this needs a matrix.
Splicing two different length vectors based on their respective index vectors containing global addresses to new vectors

Splicing two different length vectors based on their respective index vectors containing global addresses to new vectors

By : user2238658
Date : March 29 2020, 07:55 AM
will be helpful for those in need One approach that occurs to me is to do a parallel binary search, taking each value from the global index vector, and seeing if it has a match in the key vector. If it has a match in the key vector, then place the corresponding value in the result. If it does not have a match in the key vector, then place 0 in the result.
So for each position in:
code :
indy[]={1, 2, 3, 4};
#include <iostream>
#include <thrust/device_vector.h>
#include <thrust/binary_search.h>
#include <thrust/copy.h>

#define MAX_DSIZE 32768
#define nTPB 256

struct extend_functor
  int vec_len;
  int *vec1;
  float *vec2;
  extend_functor(int *_vec1, int _vec_len, float *_vec2) : vec1(_vec1), vec2(_vec2),  vec_len(_vec_len) {};
  template <typename Tuple>
  __device__ __host__
  void operator()(const Tuple &my_tuple) {
    float result = 0.0f;
    if (thrust::get<1>(my_tuple) < vec_len)
      if (thrust::get<0>(my_tuple) == vec1[thrust::get<1>(my_tuple)]) result = vec2[thrust::get<1>(my_tuple)];
    thrust::get<2>(my_tuple) = result;


// binary search, looking for key in a

__device__ void bsearch_range(const int *a, const int key, const unsigned len_a, unsigned *idx){
  unsigned lower = 0;
  unsigned upper = len_a;
  unsigned midpt;
  while (lower < upper){
    midpt = (lower + upper)>>1;
    if (a[midpt] < key) lower = midpt +1;
    else upper = midpt;
  *idx = lower;

// k is the key vector
// g is the global index vector
// v is the value vector
// r is the result vector

__global__ void extend_kernel(const int *k, const unsigned len_k, const int *g,  const unsigned len_g, const float *v, float *r){
  unsigned idx = (blockDim.x * blockIdx.x) + threadIdx.x;
  if (idx < len_g) {
    unsigned my_idx;
    int g_key = g[idx];
    bsearch_range(k, g_key, len_k, &my_idx);
    int my_key = -1;
    if (my_idx < len_k)
      my_key = k[my_idx];
    float my_val;
    if (g_key == my_key) my_val = v[my_idx];
    else my_val = 0.0f;
    r[idx] = my_val;

int main(){

  int len_x = 7;
  int len_y = 4;
  int len_g = 9;
  int indx[]={0,2,4,6,8,10,12};
  int indy[]={1, 2, 3, 4};
  float dnx[]={91.0f,92.0f,93.0f,94.0f,95.0f,96.0f,97.0f};
  float dny[]={61.0f,62.0f,63.0f,64.0f};
  int ind[]={0,1,2,3,4,6,8,10,12};

  int *h_k, *d_k, *h_g, *d_g;
  float *h_v, *d_v, *h_r, *d_r;

  h_k = (int *)malloc(MAX_DSIZE*sizeof(int));
  h_g = (int *)malloc(MAX_DSIZE*sizeof(int));
  h_v = (float *)malloc(MAX_DSIZE*sizeof(float));
  h_r = (float *)malloc(MAX_DSIZE*sizeof(float));

  cudaMalloc(&d_k, MAX_DSIZE*sizeof(int));
  cudaMalloc(&d_g, MAX_DSIZE*sizeof(int));
  cudaMalloc(&d_v, MAX_DSIZE*sizeof(float));
  cudaMalloc(&d_r, MAX_DSIZE*sizeof(float));

// test case x

  memcpy(h_k, indx, len_x*sizeof(int));
  memcpy(h_g, ind, len_g*sizeof(int));
  memcpy(h_v, dnx, len_x*sizeof(float));

  cudaMemcpy(d_k, h_k, len_x*sizeof(int), cudaMemcpyHostToDevice);
  cudaMemcpy(d_g, h_g, len_g*sizeof(int), cudaMemcpyHostToDevice);
  cudaMemcpy(d_v, h_v, len_x*sizeof(float), cudaMemcpyHostToDevice);
  extend_kernel<<<(len_g+nTPB-1)/nTPB, nTPB >>>(d_k, len_x, d_g, len_g, d_v, d_r);
  cudaMemcpy(h_r, d_r, len_g*sizeof(float), cudaMemcpyDeviceToHost);

  std::cout << "case x result: ";
  for (int i=0; i < len_g; i++)
    std::cout << h_r[i] << " ";
  std::cout << std::endl;

// test case y

  memcpy(h_k, indy, len_y*sizeof(int));
  memcpy(h_g, ind, len_g*sizeof(int));
  memcpy(h_v, dny, len_y*sizeof(float));

  cudaMemcpy(d_k, h_k, len_y*sizeof(int), cudaMemcpyHostToDevice);
  cudaMemcpy(d_g, h_g, len_g*sizeof(int), cudaMemcpyHostToDevice);
  cudaMemcpy(d_v, h_v, len_y*sizeof(float), cudaMemcpyHostToDevice);
  extend_kernel<<<(len_g+nTPB-1)/nTPB, nTPB >>>(d_k, len_y, d_g, len_g, d_v, d_r);
  cudaMemcpy(h_r, d_r, len_g*sizeof(float), cudaMemcpyDeviceToHost);

  std::cout << "case y result: ";
  for (int i=0; i < len_g; i++)
    std::cout << h_r[i] << " ";
  std::cout << std::endl;

// using thrust

  thrust::device_vector<int> tind(ind, ind+len_g);
  thrust::device_vector<int> tindx(indx, indx+len_x);
  thrust::device_vector<float> tdnx(dnx, dnx+len_x);
  thrust::device_vector<float> tresult(len_g);

  thrust::device_vector<int> tbound(len_g);
  thrust::lower_bound(tindx.begin(), tindx.end(), tind.begin(), tind.end(), tbound.begin());
  thrust::for_each(thrust::make_zip_iterator(thrust::make_tuple(tind.begin(), tbound.begin(), tresult.begin())), thrust::make_zip_iterator(thrust::make_tuple(tind.end(), tbound.end(), tresult.end())), extend_functor(thrust::raw_pointer_cast(tindx.data()), len_x, thrust::raw_pointer_cast(tdnx.data())));

  std::cout << "thrust case x result: ";
  thrust::copy(tresult.begin(), tresult.end(), std::ostream_iterator<float>(std::cout, " "));
  std::cout << std::endl;
  return 0;
Sorting two column vectors into 3D matrix based on position

Sorting two column vectors into 3D matrix based on position

By : user3382685
Date : March 29 2020, 07:55 AM
Any of those help I've developed a solution, which works for my case but might not be as robust as required for some. It requires a known number of dots in a 'square' grid and a rough idea of the spacing between the dots. I find the 'AlphaShape' of the dots and all the points that lie along the edge. The edge vector is shifted to start at the minimum and then wrapped around a matrix with the corresponding points are discarded from the list of vertices. Probably not the best idea for large point clouds but good enough for me.
code :
R = 50; % search radius
xy = centres2;
x = centres2(:,1);
y = centres2(:,2);

for i = 1:8
    T = delaunay(xy); % delaunay
    [~,r] = circumcenter(triangulation(T,x,y)); % circumcenters
    T = T(r < R,:); % points within radius
    B = freeBoundary(triangulation(T,x,y)); % find edge vertices
    A = B(:,1);

    EdgeList = [x(A) y(A) x(A)+y(A)]; % find point closest to origin and rotate vector
    [~,I] = min(EdgeList);
    EdgeList = circshift(EdgeList,-I(3)+1);

    n = sqrt(length(xy)); % define zeros matrix
    matX = zeros(n); % wrap x vector around zeros matrix
    matX(1,1:n) = EdgeList(1:n,1);
    matX(2:n-1,n) = EdgeList(n+1:(2*n)-2,1);
    matX(n,n:-1:1) = EdgeList((2*n)-1:(3*n)-2,1);
    matX(n-1:-1:2,1) = EdgeList((3*n)-1:(4*n)-4,1);

    matY = zeros(n); % wrap y vector around zeros matrix
    matY(1,1:n) = EdgeList(1:n,2);
    matY(2:n-1,n) = EdgeList(n+1:(2*n)-2,2);
    matY(n,n:-1:1) = EdgeList((2*n)-1:(3*n)-2,2);
    matY(n-1:-1:2,1) = EdgeList((3*n)-1:(4*n)-4,2);

    centreMatX(i:n+i-1,i:n+i-1) = matX; % paste into main matrix
    centreMatY(i:n+i-1,i:n+i-1) = matY;

    xy(B(:,1),:) = 0; % discard values
    xy = xy(all(xy,2),:);   
    x = xy(:,1);
    y = xy(:,2);   


centreMatX(centreMatX == 0) = x;
centreMatY(centreMatY == 0) = y;
Sorting a list of unequal-size vectors in r

Sorting a list of unequal-size vectors in r

By : Sarah Small-Doom
Date : March 29 2020, 07:55 AM
may help you . Suppose I have several vectors - maybe they're stored in a list, but if there's a better data structure that's fine too:
code :
ll <- list(c(1,3,2),
sortfun <- function(l) {
  l1 <- lapply(l, function(x, n) {
    length(x) <- n
  }, n = max(lengths(l)))
  l1 <- do.call(rbind.data.frame, l1)
  l[do.call(order, l1)] #order's default is na.last = TRUE


#[1] 1 2
#[1] 1 3 1
#[1] 1 3 2
#[1] 2 1
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