--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Meerwald-dir/sort.c	Fri Dec 20 13:08:59 2024 +0100
@@ -0,0 +1,184 @@
+#include "sort.h"
+
+#define SWAP_GRAY(A, B) {gray t = A; A = B; B = t;}
+
+/*
+ * quicksort-alike, from the EMX library (emx/src/lib/misc/qsort.c)
+ *   by Eberhard Mattes
+ *
+ *   sort() is not stable, the order of equal elements is not defined
+ */
+
+void _sort_grays(gray *l, gray *r) {
+  gray *i;
+  gray *j;
+  gray *x;
+
+redo:
+  i = l;
+  j = r;
+  x = l + sizeof(gray) * (((r-l) / sizeof(gray)) / 2);
+
+  do {
+    while (i != x && *i < *x)
+      i++;
+    while (j != x && *j > *x)
+      j--;
+    if (i < j) {
+      SWAP_GRAY(*i, *j);
+      if (x == i)
+        x = j;
+      else if (x == j)
+        x = i;
+    }
+    if (i <= j) {
+      i++;
+      if (j > l)
+        j--;
+    }
+  } while (i <= j);
+
+  if (j-l < r-i) {
+    if (l < j)
+      _sort_grays(l, j);
+    if (i < r) {
+      l = i;
+      goto redo;
+    }
+  }
+  else {
+    if (i < r)
+      _sort_grays(i, r);
+    if (l < j) {
+      r = j;
+      goto redo;
+    }
+  }
+}
+
+void sort_grays(gray a[], int n) {
+  if (n > 1)
+    _sort_grays(&a[0], &a[n-1]);
+}
+
+/*
+ * select_largest(), from the Numeric Recipes in C, Chapter 8, p. 344,
+ *   see http://www.nr.com
+ *
+ *   returns in largest[0..m-1] the largest m elements of array[0..n-1]
+ *   with largest[0] guaranteed to be the mth largest element; largest[] is
+ *   not sorted; the array[] is not altered; this function should be used
+ *   only when m << n
+ */
+
+void select_largest_grays(gray array[], int n, int m, gray largest[]) {
+  int i, j, k;
+
+  if (m <= 0 || m > n/2)
+    return;
+
+  for (i = 0; i < m; i++)
+    largest[i] = array[i];
+  sort_grays(largest, m);
+
+  for (i = m; i < n; i++) {
+    if (array[i] > largest[0]) {
+      largest[0] = array[i];
+      j = 0;
+      k = 1;
+      while (k < m) {
+        if (k < m-1 && largest[k] > largest[k+1])
+          k++;
+        if (largest[j] <= largest[k])
+          break;
+        SWAP_GRAY(largest[k], largest[j]);
+        j = k;
+        k = k << 1;
+      }
+    }
+  }
+}
+
+#define SWAP_DOUBLE(A, B) {double t = A; A = B; B = t;}
+
+void _sort_coeffs(double *l, double *r) {
+  double *i;
+  double *j;
+  double *x;
+
+redo:
+  i = l;
+  j = r;
+  x = l + sizeof(double) * (((r-l) / sizeof(double)) / 2);
+
+  do {
+    while (i != x && *i < *x)
+      i++;
+    while (j != x && *j > *x)
+      j--;
+    if (i < j) {
+      SWAP_DOUBLE(*i, *j);
+      if (x == i)
+        x = j;
+      else if (x == j)
+        x = i;
+    }
+    if (i <= j) {
+      i++;
+      if (j > l)
+        j--;
+    }
+  } while (i <= j);
+
+  if (j-l < r-i) {
+    if (l < j)
+      _sort_coeffs(l, j);
+    if (i < r) {
+      l = i;
+      goto redo;
+    }
+  }
+  else {
+    if (i < r)
+      _sort_coeffs(i, r);
+    if (l < j) {
+      r = j;
+      goto redo;
+    }
+  }
+}
+
+void sort_coeffs(double a[], int n) {
+  if (n > 1)
+    _sort_coeffs(&a[0], &a[n-1]);
+}
+
+void select_largest_coeffs(double array[], int n, int m, double largest[]) {
+  int i, j, k;
+
+  if (m <= 0 || m > n/2)
+    return;
+
+  for (i = 0; i < m; i++)
+    largest[i] = array[i];
+  sort_coeffs(largest, m);
+
+  for (i = m; i < n; i++) {
+    if (array[i] > largest[0]) {
+      largest[0] = array[i];
+      j = 0;
+      k = 1;
+      while (k < m) {
+        if (k < m-1 && largest[k] > largest[k+1])
+          k++;
+        if (largest[j] <= largest[k])
+          break;
+        SWAP_DOUBLE(largest[k], largest[j]);
+        j = k;
+        k = k << 1;
+      }
+    }
+  }
+}
+
+