move quickselect to squiggle_more.c

scratchpad/quickselect/makefile

@@ -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

scratchpad/quickselect/quickselect.c

@@ -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;
-}

squiggle.c

@@ -196,6 +196,16 @@ double array_std(double* array, int length)
     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
 double sample_mixture(double (*samplers[])(uint64_t*), double* weights, int n_dists, uint64_t* seed)
 {

squiggle_more.c

@@ -30,6 +30,51 @@ typedef struct ci_searcher_t {
     int remaining;
 } 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)
 {
     int n = 100 * 1000;