Add exmaple.c

Author: Raghuveer Devulapalli

example.c

@@ -0,0 +1,73 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+// declare function here, linker will find this when linked to
+// libx86simdsortcpp.so
+void keyvalue_qsort_float_sizet(float*, size_t*, size_t);
+void keyvalue_qsort_float_uint32(float*, uint32_t*, uint32_t);
+
+// struct definition, we will sort an array of these:
+struct Point {
+    int x;
+    int y;
+    float distance;
+};
+
+#define SWAP(a, b, type) {type temp = a; a = b; b = temp;}
+
+// Function to sort an array of objects:
+void object_qsort(struct Point* arr, size_t size)
+{
+    /* (1) Create and initialize arrays of key and value  */
+    float* key = malloc(size * sizeof(float));
+    size_t* arg = malloc(size * sizeof(size_t));
+    bool* done = malloc(size * sizeof(bool));
+    for (size_t ii = 0; ii < size; ++ii) {
+        key[ii] = arr[ii].distance;
+        arg[ii] = ii;
+        done[ii] = false;
+    }
+
+    /* (2) IndexSort using the keyvalue_qsort */
+    keyvalue_qsort_float_sizet(key, arg, size);
+
+    /* (3) Permute obj array in-place */
+    for (size_t ii = 0; ii < size; ++ii) {
+        if (done[ii]) { continue; }
+        done[ii] = true;
+        size_t prev_j = ii;
+        size_t jj = arg[ii];
+        while (ii != jj) {
+            SWAP(arr[prev_j], arr[jj], struct Point);
+            done[jj] = true;
+            prev_j = jj;
+            jj = arg[jj];
+        }
+    }
+    free(key);
+    free(arg);
+    free(done);
+}
+
+int main() {
+    const size_t size = 10;
+    struct Point arr[size];
+
+    // Initialize:
+    for (size_t ii = 0; ii < size; ++ii) {
+        arr[ii].distance = (float) rand() / RAND_MAX;
+    }
+
+    // sort:
+    object_qsort(arr, size);
+
+    // check if it is sorted:
+    printf("arr = ");
+    for (size_t ii = 0; ii < size; ++ii) {
+        printf("%f, ", arr[ii].distance);
+    }
+    printf("\n");
+    return 0;
+}