add for hw4

hws/hw4/rngutil.c

@@ -0,0 +1,90 @@
+#include "rngutil.h"
+
+Interval *new_interval(size_t n_int) {
+    Interval *x = malloc(sizeof(Interval));
+    x->n_interval = n_int;
+    x->indexed = calloc(n_int, sizeof(size_t));
+    return x;
+}
+
+void free_interval(Interval *x) {
+    free(x->indexed);
+    free(x);
+}
+
+void intervalizing(Interval *interval, size_t n,
+                   float *samples /* samples must be sorted */) {
+
+    float lo = samples[0];
+    float hi = samples[n - 1];
+
+    float dx = (hi - lo) / interval->n_interval;
+
+    float curr = lo + dx;
+
+    size_t i = 0;
+    size_t ind = 0;
+    while (i < n) {
+        if (samples[i] < curr) {
+            i++;
+        } else {
+            if (ind == interval->n_interval - 1) {
+                interval->indexed[ind] = n;
+            } else {
+                interval->indexed[ind] = i;
+            }
+
+            ind++;
+            curr = lo + (ind + 1) * dx;
+        }
+    }
+    if (interval->indexed[interval->n_interval - 1] != n) {
+        interval->indexed[interval->n_interval - 1] = n;
+    }
+}
+
+void print_histogram(Interval *interval, size_t n, float *samples) {
+    size_t n_interval = interval->n_interval;
+    size_t prev_cum_count = 0;
+
+    const int MAX_STARS = 80;
+
+    double avg_count = (double) n / (double) n_interval;
+    double scale_max = avg_count * 4;
+    printf("------------------------------------------------------\n");
+    printf("# Histogram (n_samples: %zu, avg_bin: %.2f) #\n",
+           n, avg_count);
+    printf("# (scale ref.: %.2f count = %d stars) #\n",
+           scale_max, MAX_STARS);
+    printf("# min: %6.2f, max: %6.2f\n",
+           samples[0], samples[n - 1]);
+    size_t i, j;
+    for (i = 0; i < n_interval; i++) {
+        size_t current_cumulative_count = interval->indexed[i];
+        size_t individual_count = current_cumulative_count - prev_cum_count;
+
+        if (current_cumulative_count < prev_cum_count) {
+            printf("!\n");
+            individual_count = 0;
+        }
+
+        int num_stars = (int) (((double) individual_count / scale_max) * MAX_STARS);
+
+        if (num_stars > MAX_STARS) {
+            num_stars = MAX_STARS;
+        }
+
+        printf("Bin %3zu: [%8zu](%5.2f%%) | ", i, individual_count, (double) individual_count / (double) n * 100.0);
+        for (j = 0; j < num_stars; j++) {
+            printf("*");
+        }
+
+        if (num_stars == MAX_STARS && (double) individual_count > scale_max) {
+            printf("+");
+        }
+        printf("\n");
+
+        prev_cum_count = current_cumulative_count;
+    }
+    printf("------------------------------------------------------\n");
+}