move quickselect to squiggle_more.c

This commit is contained in:
NunoSempere 2023-11-29 21:49:22 +00:00
parent dc3f7eed4d
commit 3e4360f930
5 changed files with 55 additions and 80 deletions

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@ -1,11 +0,0 @@
build:
gcc quickselect.c -lm -o quickselect
run:
./quickselect
## Formatter
STYLE_BLUEPRINT=webkit
FORMATTER=clang-format -i -style=$(STYLE_BLUEPRINT)
format:
$(FORMATTER) quickselect.c

Binary file not shown.

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@ -1,69 +0,0 @@
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
void swp(int i, int j, double xs[])
{
double tmp = xs[i];
xs[i] = xs[j];
xs[j] = tmp;
}
void array_print(double xs[], int n)
{
printf("[");
for (int i = 0; i < n; i++) {
printf("%f, ", xs[i]);
}
printf("]\n");
}
int partition(int low, int high, double xs[], int length)
{
// To understand this function:
// - see the note after gt variable definition
// - go to commit 578bfa27 and the scratchpad/ folder in it, which has printfs sprinkled throughout
int pivot = low + floor((high - low) / 2);
double pivot_value = xs[pivot];
swp(pivot, high, xs);
int gt = low; /* This pointer will iterate until finding an element which is greater than the pivot. Then it will move elements that are smaller before it--more specifically, it will move elements to its position and then increment. As a result all elements between gt and i will be greater than the pivot. */
for (int i = low; i < high; i++) {
if (xs[i] < pivot_value) {
swp(gt, i, xs);
gt++;
}
}
swp(high, gt, xs);
return gt;
}
double quickselect(int k, double xs[], int length)
{
int low = 0;
int high = length - 1;
for (;;) {
if (low == high) {
return xs[low];
}
int pivot = partition(low, high, xs, length);
if (pivot == k) {
return xs[pivot];
} else if (k < pivot) {
high = pivot - 1;
} else {
low = pivot + 1;
}
}
}
int main()
{
double xs[] = { 2.1, 1.0, 6.0, 4.0, 7.0, -1.0, 2.0, 10.0 };
int length = 8;
int k = 2;
array_print(xs, 8);
double result = quickselect(k, xs, length);
printf("The item in pos #%d is: %f\n", k, result);
array_print(xs, 8);
return 0;
}

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@ -196,6 +196,16 @@ double array_std(double* array, int length)
return std; return std;
} }
void array_print(double xs[], int n)
{
printf("[");
for (int i = 0; i < n - 1; i++) {
printf("%f, ", xs[i]);
}
printf("%f", xs[n - 1]);
printf("]\n");
}
// Mixture function // Mixture function
double sample_mixture(double (*samplers[])(uint64_t*), double* weights, int n_dists, uint64_t* seed) double sample_mixture(double (*samplers[])(uint64_t*), double* weights, int n_dists, uint64_t* seed)
{ {

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@ -30,6 +30,51 @@ typedef struct ci_searcher_t {
int remaining; int remaining;
} ci_searcher; } ci_searcher;
void swp(int i, int j, double xs[])
{
double tmp = xs[i];
xs[i] = xs[j];
xs[j] = tmp;
}
int partition(int low, int high, double xs[], int length)
{
// To understand this function:
// - see the note after gt variable definition
// - go to commit 578bfa27 and the scratchpad/ folder in it, which has printfs sprinkled throughout
int pivot = low + floor((high - low) / 2);
double pivot_value = xs[pivot];
swp(pivot, high, xs);
int gt = low; /* This pointer will iterate until finding an element which is greater than the pivot. Then it will move elements that are smaller before it--more specifically, it will move elements to its position and then increment. As a result all elements between gt and i will be greater than the pivot. */
for (int i = low; i < high; i++) {
if (xs[i] < pivot_value) {
swp(gt, i, xs);
gt++;
}
}
swp(high, gt, xs);
return gt;
}
double quickselect(int k, double xs[], int length)
{
int low = 0;
int high = length - 1;
for (;;) {
if (low == high) {
return xs[low];
}
int pivot = partition(low, high, xs, length);
if (pivot == k) {
return xs[pivot];
} else if (k < pivot) {
high = pivot - 1;
} else {
low = pivot + 1;
}
}
}
ci get_90_confidence_interval(double (*sampler)(uint64_t*), uint64_t* seed) ci get_90_confidence_interval(double (*sampler)(uint64_t*), uint64_t* seed)
{ {
int n = 100 * 1000; int n = 100 * 1000;