src/oping.c: Add median and 'n'th percentile, remove average and stddev.
[liboping.git] / src / oping.c
index 0cb084f..ff06670 100644 (file)
@@ -1,6 +1,6 @@
 /**
  * Object oriented C module to send ICMP and ICMPv6 `echo's.
- * Copyright (C) 2006-2011  Florian octo Forster <ff at octo.it>
+ * Copyright (C) 2006-2014  Florian octo Forster <ff at octo.it>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
 #endif
 
 #include <locale.h>
+#include <langinfo.h>
 
 #if USE_NCURSES
 # define NCURSES_OPAQUE 1
 /* http://newsgroups.derkeiler.com/Archive/Rec/rec.games.roguelike.development/2010-09/msg00050.html */
 # define _X_OPEN_SOURCE_EXTENDED
-# include <ncursesw/ncurses.h>
 
-/* some evilness: ncurses knows how to detect unicode, but won't
-   expose it, yet there's this function that does what we want, so we
-   steal it away from it */
-extern int    _nc_unicode_locale(void);
+# if HAVE_NCURSESW_NCURSES_H
+#  include <ncursesw/ncurses.h>
+# elif HAVE_NCURSES_H
+#  include <ncurses.h>
+# endif
 
 # define OPING_GREEN 1
 # define OPING_YELLOW 2
@@ -94,6 +95,9 @@ extern int    _nc_unicode_locale(void);
 # define OPING_YELLOW_HIST 5
 # define OPING_RED_HIST 6
 
+double const threshold_green = 0.8;
+double const threshold_yellow = 0.95;
+
 static char const * const hist_symbols_utf8[] = {
        "▁", "▂", "▃", "▄", "▅", "▆", "▇", "█" };
 static size_t const hist_symbols_utf8_num = sizeof (hist_symbols_utf8)
@@ -121,12 +125,27 @@ static size_t const hist_colors_num = sizeof (hist_colors_utf8)
        / sizeof (hist_colors_utf8[0]);
 #endif
 
+/* "─" */
+#define BOXPLOT_WHISKER_BAR       (113 | A_ALTCHARSET)
+/* "├" */
+#define BOXPLOT_WHISKER_LEFT_END  (116 | A_ALTCHARSET)
+/* "┤" */
+#define BOXPLOT_WHISKER_RIGHT_END (117 | A_ALTCHARSET)
+/* Inverted */
+#define BOXPLOT_BOX               ' '
+/* "│", inverted */
+#define BOXPLOT_MEDIAN            (120 | A_ALTCHARSET)
+
 #include "oping.h"
 
 #ifndef _POSIX_SAVED_IDS
 # define _POSIX_SAVED_IDS 0
 #endif
 
+#ifndef IPTOS_MINCOST
+# define IPTOS_MINCOST 0x02
+#endif
+
 /* Remove GNU specific __attribute__ settings when using another compiler */
 #if !__GNUC__
 # define __attribute__(x) /**/
@@ -144,7 +163,13 @@ typedef struct ping_context
        double latency_min;
        double latency_max;
        double latency_total;
-       double latency_total_square;
+
+/* 1000 + one "infinity" bucket. */
+#define OPING_HISTOGRAM_BUCKETS 1001
+       uint32_t *histogram_counters;
+       uint32_t *histogram_accumulated;
+       double *histogram_ratio;
+       size_t latency_histogram_size;
 
 #if USE_NCURSES
        WINDOW *window;
@@ -159,6 +184,13 @@ static char   *opt_filename   = NULL;
 static int     opt_count      = -1;
 static int     opt_send_ttl   = 64;
 static uint8_t opt_send_qos   = 0;
+#define OPING_DEFAULT_PERCENTILE 95.0
+static double  opt_percentile = -1.0;
+static double  opt_exit_status_threshold = 1.0;
+#if USE_NCURSES
+static int     opt_show_graph = 1;
+static int     opt_utf8       = 0;
+#endif
 
 static int host_num = 0;
 
@@ -186,7 +218,14 @@ static ping_context_t *context_create (void) /* {{{ */
        ret->latency_min   = -1.0;
        ret->latency_max   = -1.0;
        ret->latency_total = 0.0;
-       ret->latency_total_square = 0.0;
+
+       ret->latency_histogram_size = (size_t) OPING_HISTOGRAM_BUCKETS;
+       ret->histogram_counters = calloc (ret->latency_histogram_size,
+                       sizeof (*ret->histogram_counters));
+       ret->histogram_accumulated = calloc (ret->latency_histogram_size,
+                       sizeof (*ret->histogram_accumulated));
+       ret->histogram_ratio = calloc (ret->latency_histogram_size,
+                       sizeof (*ret->histogram_ratio));
 
 #if USE_NCURSES
        ret->window = NULL;
@@ -208,40 +247,50 @@ static void context_destroy (ping_context_t *context) /* {{{ */
        }
 #endif
 
+       free (context->histogram_counters);
+       context->histogram_counters = NULL;
+
+       free (context->histogram_accumulated);
+       context->histogram_accumulated = NULL;
+
+       free (context->histogram_ratio);
+       context->histogram_ratio = NULL;
+
        free (context);
 } /* }}} void context_destroy */
 
-static double context_get_average (ping_context_t *ctx) /* {{{ */
+static double context_get_percentile (ping_context_t *ctx, /* {{{ */
+               double percentile)
 {
-       double num_total;
+       double threshold = percentile / 100.0;
+       double index_to_ms_factor;
+       size_t i;
+       double ret;
 
-       if (ctx == NULL)
-               return (-1.0);
+       if (ctx->histogram_ratio == NULL)
+               return (NAN);
 
-       if (ctx->req_rcvd < 1)
-               return (-0.0);
+       for (i = 0; i < ctx->latency_histogram_size; i++)
+               if (ctx->histogram_ratio[i] >= threshold)
+                       break;
 
-       num_total = (double) ctx->req_rcvd;
-       return (ctx->latency_total / num_total);
-} /* }}} double context_get_average */
+       if (i >= ctx->latency_histogram_size)
+               return (NAN);
+       else if (i == (ctx->latency_histogram_size - 1))
+               return (INFINITY);
 
-static double context_get_stddev (ping_context_t *ctx) /* {{{ */
-{
-       double num_total;
+       index_to_ms_factor = (1000.0 * opt_interval) / (ctx->latency_histogram_size - 1);
 
-       if (ctx == NULL)
-               return (-1.0);
+       /* Multiply with i+1, because we're interested in the _upper_ bound of
+        * each bucket. */
+       ret = (index_to_ms_factor * ((double) (i + 1)));
 
-       if (ctx->req_rcvd < 1)
-               return (-0.0);
-       else if (ctx->req_rcvd < 2)
-               return (0.0);
+       /* Avoid reporting a higher latency than latency_max. */
+       if (ret > ctx->latency_max)
+               ret = ctx->latency_max;
 
-       num_total = (double) ctx->req_rcvd;
-       return (sqrt (((num_total * ctx->latency_total_square)
-                                       - (ctx->latency_total * ctx->latency_total))
-                               / (num_total * (num_total - 1.0))));
-} /* }}} double context_get_stddev */
+       return (ret);
+} /* }}} double context_get_percentile */
 
 static double context_get_packet_loss (const ping_context_t *ctx) /* {{{ */
 {
@@ -303,6 +352,13 @@ static void usage_exit (const char *name, int status) /* {{{ */
                        "  -I srcaddr   source address\n"
                        "  -D device    outgoing interface name\n"
                        "  -f filename  filename to read hosts from\n"
+#if USE_NCURSES
+                       "  -u / -U      force / disable UTF-8 output\n"
+                       "  -g graph     graph type to draw\n"
+#endif
+                       "  -P percent   Report the n'th percentile of latency\n"
+                       "  -Z percent   Exit with non-zero exit status if more than this percentage of\n"
+                       "               probes timed out. (default: never)\n"
 
                        "\noping "PACKAGE_VERSION", http://verplant.org/liboping/\n"
                        "by Florian octo Forster <octo@verplant.org>\n"
@@ -505,7 +561,11 @@ static int read_options (int argc, char **argv) /* {{{ */
 
        while (1)
        {
-               optchar = getopt (argc, argv, "46c:hi:I:t:Q:f:D:");
+               optchar = getopt (argc, argv, "46c:hi:I:t:Q:f:D:Z:P:"
+#if USE_NCURSES
+                               "uUg:"
+#endif
+                               );
 
                if (optchar == -1)
                        break;
@@ -522,7 +582,12 @@ static int read_options (int argc, char **argv) /* {{{ */
                                        int new_count;
                                        new_count = atoi (optarg);
                                        if (new_count > 0)
+                                       {
                                                opt_count = new_count;
+
+                                               if ((opt_percentile < 0.0) && (opt_count < 20))
+                                                       opt_percentile = 100.0 * (opt_count - 1) / opt_count;
+                                       }
                                        else
                                                fprintf(stderr, "Ignoring invalid count: %s\n",
                                                                optarg);
@@ -548,6 +613,7 @@ static int read_options (int argc, char **argv) /* {{{ */
                                                opt_interval = new_interval;
                                }
                                break;
+
                        case 'I':
                                {
                                        if (opt_srcaddr != NULL)
@@ -576,14 +642,72 @@ static int read_options (int argc, char **argv) /* {{{ */
                                set_opt_send_qos (optarg);
                                break;
 
+                       case 'P':
+                               {
+                                       double new_percentile;
+                                       new_percentile = atof (optarg);
+                                       if (isnan (new_percentile)
+                                                       || (new_percentile < 0.1)
+                                                       || (new_percentile > 100.0))
+                                               fprintf (stderr, "Ignoring invalid percentile: %s\n",
+                                                               optarg);
+                                       else
+                                               opt_percentile = new_percentile;
+                               }
+                               break;
+
+#if USE_NCURSES
+                       case 'g':
+                               if (strcasecmp ("none", optarg) == 0)
+                                       opt_show_graph = 0;
+                               else if (strcasecmp ("prettyping", optarg) == 0)
+                                       opt_show_graph = 1;
+                               else if (strcasecmp ("boxplot", optarg) == 0)
+                                       opt_show_graph = 2;
+                               else if (strcasecmp ("histogram", optarg) == 0)
+                                       opt_show_graph = 3;
+                               else
+                                       fprintf (stderr, "Unknown graph option: %s\n", optarg);
+                               break;
+
+                       case 'u':
+                               opt_utf8 = 2;
+                               break;
+                       case 'U':
+                               opt_utf8 = 1;
+                               break;
+#endif
+
+                       case 'Z':
+                       {
+                               char *endptr = NULL;
+                               double tmp;
+
+                               errno = 0;
+                               tmp = strtod (optarg, &endptr);
+                               if ((errno != 0) || (endptr == NULL) || (*endptr != 0) || (tmp < 0.0) || (tmp > 100.0))
+                               {
+                                       fprintf (stderr, "Ignoring invalid -Z argument: %s\n", optarg);
+                                       fprintf (stderr, "The \"-Z\" option requires a numeric argument between 0 and 100.\n");
+                               }
+                               else
+                                       opt_exit_status_threshold = tmp / 100.0;
+
+                               break;
+                       }
+
                        case 'h':
                                usage_exit (argv[0], 0);
                                break;
+
                        default:
                                usage_exit (argv[0], 1);
                }
        }
 
+       if (opt_percentile <= 0.0)
+               opt_percentile = OPING_DEFAULT_PERCENTILE;
+
        return (optind);
 } /* }}} read_options */
 
@@ -635,14 +759,112 @@ static void time_calc (struct timespec *ts_dest, /* {{{ */
 } /* }}} void time_calc */
 
 #if USE_NCURSES
-static int update_prettyping_graph (ping_context_t *ctx, /* {{{ */
+static _Bool has_utf8() /* {{{ */
+{
+# if HAVE_NCURSESW_NCURSES_H
+       if (!opt_utf8)
+       {
+               /* Automatically determine */
+               if (strcasecmp ("UTF-8", nl_langinfo (CODESET)) == 0)
+                       opt_utf8 = 2;
+               else
+                       opt_utf8 = 1;
+       }
+       return ((_Bool) (opt_utf8 - 1));
+# else
+       return (0);
+# endif
+} /* }}} _Bool has_utf8 */
+
+static int update_graph_boxplot (ping_context_t *ctx) /* {{{ */
+{
+       double *ratios;
+       size_t i;
+       size_t x_max;
+       size_t x;
+
+       x_max = (size_t) getmaxx (ctx->window);
+       if (x_max <= 8)
+               return (EINVAL);
+       x_max -= 4;
+
+       ratios = calloc (x_max, sizeof (*ratios));
+
+       /* Downsample */
+       for (i = 0; i < ctx->latency_histogram_size; i++)
+       {
+               x = i * x_max / ctx->latency_histogram_size;
+               ratios[x] = ctx->histogram_ratio[i];
+       }
+
+       for (x = 0; x < x_max; x++)
+       {
+               int symbol = ' ';
+               _Bool reverse = 0;
+
+               if (x == 0)
+               {
+                       if (ratios[x] >= 0.5)
+                       {
+                               symbol = BOXPLOT_MEDIAN;
+                               reverse = 1;
+                       }
+                       else if (ratios[x] > 0.25)
+                       {
+                               symbol = BOXPLOT_BOX;
+                               reverse = 1;
+                       }
+                       else if (ratios[x] > 0.025)
+                               symbol = BOXPLOT_WHISKER_BAR;
+                       else
+                               symbol = ' '; /* NOP */
+               }
+               else /* (x != 0) */
+               {
+                       if ((ratios[x - 1] < 0.5) && (ratios[x] >= 0.5))
+                       {
+                               symbol = BOXPLOT_MEDIAN;
+                               reverse = 1;
+                       }
+                       else if (((ratios[x] >= 0.25) && (ratios[x] <= 0.75))
+                                       || ((ratios[x - 1] < 0.75) && (ratios[x] > 0.75)))
+                       {
+                               symbol = BOXPLOT_BOX;
+                               reverse = 1;
+                       }
+                       else if ((ratios[x] < 0.5) && (ratios[x] >= 0.025))
+                       {
+                               if (ratios[x - 1] < 0.025)
+                                       symbol = BOXPLOT_WHISKER_LEFT_END;
+                               else
+                                       symbol = BOXPLOT_WHISKER_BAR;
+                       }
+                       else if ((ratios[x] > .5) && (ratios[x] < 0.975))
+                       {
+                               symbol = BOXPLOT_WHISKER_BAR;
+                       }
+                       else if ((ratios[x] >= 0.975) && (ratios[x - 1] < 0.975))
+                               symbol = BOXPLOT_WHISKER_RIGHT_END;
+               }
+
+               if (reverse)
+                       wattron (ctx->window, A_REVERSE);
+               mvwaddch (ctx->window, /* y = */ 3, /* x = */ (int) (x + 2), symbol);
+               // mvwprintw (ctx->window, /* y = */ 3, /* x = */ (int) (x + 2), symbol);
+               if (reverse)
+                       wattroff (ctx->window, A_REVERSE);
+       }
+
+       free (ratios);
+       return (0);
+} /* }}} int update_graph_boxplot */
+
+static int update_graph_prettyping (ping_context_t *ctx, /* {{{ */
                double latency, unsigned int sequence)
 {
        int color = OPING_RED;
        char const *symbol = "!";
        int symbolc = '!';
-       size_t hist_symbols_num;
-       size_t index_symbols;
 
        int x_max;
        int x_pos;
@@ -650,33 +872,40 @@ static int update_prettyping_graph (ping_context_t *ctx, /* {{{ */
        x_max = getmaxx (ctx->window);
        x_pos = ((sequence - 1) % (x_max - 4)) + 2;
 
-       if (_nc_unicode_locale())
-       {
-               hist_symbols_num = hist_symbols_utf8_num;
-       }
-       else {
-               hist_symbols_num = hist_symbols_acs_num;
-       }
-
        if (latency >= 0.0)
        {
                double ratio;
-               size_t intensity;
+
+               size_t symbols_num = hist_symbols_acs_num;
+               size_t colors_num = 1;
+
+               size_t index_symbols;
                size_t index_colors;
+               size_t intensity;
 
-               ratio = latency / PING_DEF_TTL;
+               /* latency is in milliseconds, opt_interval is in seconds. */
+               ratio = (latency * 0.001) / opt_interval;
                if (ratio > 1) {
                        ratio = 1.0;
                }
 
-               intensity = (size_t) ((ratio * hist_symbols_num
-                                       * hist_colors_num) - 1);
+               if (has_utf8 ())
+                       symbols_num = hist_symbols_utf8_num;
+
+               if (has_colors () == TRUE)
+                       colors_num = hist_colors_num;
+
+               intensity = (size_t) (ratio * ((double) (symbols_num * colors_num)));
+               if (intensity >= (symbols_num * colors_num))
+                       intensity = (symbols_num * colors_num) - 1;
+
+               index_symbols = intensity % symbols_num;
+               assert (index_symbols < symbols_num);
 
-               index_colors = intensity / hist_symbols_num;
-               assert (index_colors < hist_colors_num);
+               index_colors = intensity / symbols_num;
+               assert (index_colors < colors_num);
 
-               index_symbols = intensity % hist_symbols_num;
-               if (_nc_unicode_locale())
+               if (has_utf8())
                {
                        color = hist_colors_utf8[index_colors];
                        symbol = hist_symbols_utf8[index_symbols];
@@ -686,25 +915,20 @@ static int update_prettyping_graph (ping_context_t *ctx, /* {{{ */
                        color = hist_colors_acs[index_colors];
                        symbolc = hist_symbols_acs[index_symbols] | A_ALTCHARSET;
                }
-        }
+       }
        else /* if (!(latency >= 0.0)) */
                wattron (ctx->window, A_BOLD);
 
-       wattron (ctx->window, COLOR_PAIR(color));
-       if (_nc_unicode_locale())
-       {
-               mvwprintw (ctx->window,
-                          /* y = */ 3,
-                          /* x = */ x_pos,
-                          symbol);
-       }
-       else {
-               mvwaddch (ctx->window,
-                         /* y = */ 3,
-                         /* x = */ x_pos,
-                         symbolc);
-       }
-       wattroff (ctx->window, COLOR_PAIR(color));
+       if (has_colors () == TRUE)
+               wattron (ctx->window, COLOR_PAIR(color));
+
+       if (has_utf8())
+               mvwprintw (ctx->window, /* y = */ 3, /* x = */ x_pos, symbol);
+       else
+               mvwaddch (ctx->window, /* y = */ 3, /* x = */ x_pos, symbolc);
+
+       if (has_colors () == TRUE)
+               wattroff (ctx->window, COLOR_PAIR(color));
 
        /* Use negation here to handle NaN correctly. */
        if (!(latency >= 0.0))
@@ -712,7 +936,97 @@ static int update_prettyping_graph (ping_context_t *ctx, /* {{{ */
 
        wprintw (ctx->window, " ");
        return (0);
-} /* }}} int update_prettyping_graph */
+} /* }}} int update_graph_prettyping */
+
+static int update_graph_histogram (ping_context_t *ctx) /* {{{ */
+{
+       uint32_t *counters;
+       uint32_t *accumulated;
+       uint32_t num;
+       uint32_t max;
+       size_t i;
+       size_t x_max;
+       size_t x;
+
+       size_t symbols_num = hist_symbols_acs_num;
+
+       if (has_utf8 ())
+               symbols_num = hist_symbols_utf8_num;
+
+       x_max = (size_t) getmaxx (ctx->window);
+       if (x_max <= 4)
+               return (EINVAL);
+       x_max -= 4;
+
+       counters = calloc (x_max, sizeof (*counters));
+       accumulated = calloc (x_max, sizeof (*accumulated));
+
+       /* Downsample */
+       max = 0;
+       for (i = 0; i < ctx->latency_histogram_size; i++)
+       {
+               x = i * x_max / ctx->latency_histogram_size;
+               counters[x] += ctx->histogram_counters[i];
+               accumulated[x] = counters[x];
+
+               if (max < counters[x])
+                       max = counters[x];
+       }
+
+       /* Sum */
+       for (x = 1; x < x_max; x++)
+               accumulated[x] += accumulated[x - 1];
+       num = accumulated[x_max - 1];
+
+       /* Calculate ratios */
+       for (x = 0; x < x_max; x++)
+       {
+               double height = ((double) counters[x]) / ((double) max);
+               double ratio_this = ((double) accumulated[x]) / ((double) num);
+               double ratio_prev = 0.0;
+               size_t index;
+               int color = 0;
+
+               index = (size_t) (height * ((double) symbols_num));
+               if (index >= symbols_num)
+                       index = symbols_num - 1;
+
+               if (x > 0)
+                       ratio_prev = ((double) accumulated[x - 1]) / ((double) num);
+
+               if (has_colors () == TRUE)
+               {
+                       if ((ratio_this <= threshold_green)
+                                       || ((ratio_prev < threshold_green)
+                                               && (ratio_this > threshold_green)))
+                               color = OPING_GREEN;
+                       else if ((ratio_this <= threshold_yellow)
+                                       || ((ratio_prev < threshold_yellow)
+                                               && (ratio_this > threshold_yellow)))
+                               color = OPING_YELLOW;
+                       else
+                               color = OPING_RED;
+
+                       wattron (ctx->window, COLOR_PAIR(color));
+               }
+
+               if (counters[x] == 0)
+                       mvwaddch (ctx->window, /* y = */ 3, /* x = */ x + 2, ' ');
+               else if (has_utf8 ())
+                       mvwprintw (ctx->window, /* y = */ 3, /* x = */ x + 2,
+                                       hist_symbols_utf8[index]);
+               else
+                       mvwaddch (ctx->window, /* y = */ 3, /* x = */ x + 2,
+                                       hist_symbols_acs[index] | A_ALTCHARSET);
+
+               if (has_colors () == TRUE)
+                       wattroff (ctx->window, COLOR_PAIR(color));
+
+       }
+
+       free (accumulated);
+       return (0);
+} /* }}} int update_graph_histogram */
 
 static int update_stats_from_context (ping_context_t *ctx, pingobj_iter_t *iter) /* {{{ */
 {
@@ -747,22 +1061,25 @@ static int update_stats_from_context (ping_context_t *ctx, pingobj_iter_t *iter)
                        ctx->latency_total);
        if (ctx->req_rcvd != 0)
        {
-               double average;
-               double deviation;
+               double median;
+               double percentile;
+
+               median = context_get_percentile (ctx, 50.0);
+               percentile = context_get_percentile (ctx, opt_percentile);
 
-               average = context_get_average (ctx);
-               deviation = context_get_stddev (ctx);
-                       
                mvwprintw (ctx->window, /* y = */ 2, /* x = */ 2,
-                               "rtt min/avg/max/sdev = %.3f/%.3f/%.3f/%.3f ms",
-                               ctx->latency_min,
-                               average,
-                               ctx->latency_max,
-                               deviation);
+                               "RTT[ms]: min = %.0f, median = %.0f, p(%.0f) = %.0f, max = %.0f",
+                               ctx->latency_min, median,
+                               opt_percentile, percentile,
+                               ctx->latency_max);
        }
 
-       if (has_colors () == TRUE)
-               update_prettyping_graph (ctx, latency, sequence);
+       if (opt_show_graph == 1)
+               update_graph_prettyping (ctx, latency, sequence);
+       else if (opt_show_graph == 2)
+               update_graph_boxplot (ctx);
+       else if (opt_show_graph == 3)
+               update_graph_histogram (ctx);
 
        wrefresh (ctx->window);
 
@@ -775,12 +1092,13 @@ static int on_resize (pingobj_t *ping) /* {{{ */
        int width = 0;
        int height = 0;
        int main_win_height;
+       int box_height = (opt_show_graph == 0) ? 4 : 5;
 
        getmaxyx (stdscr, height, width);
        if ((height < 1) || (width < 1))
                return (EINVAL);
 
-       main_win_height = height - (5 * host_num);
+       main_win_height = height - (box_height * host_num);
        wresize (main_win, main_win_height, /* width = */ width);
        /* Allow scrolling */
        scrollok (main_win, TRUE);
@@ -804,9 +1122,9 @@ static int on_resize (pingobj_t *ping) /* {{{ */
                        delwin (context->window);
                        context->window = NULL;
                }
-               context->window = newwin (/* height = */ 5,
+               context->window = newwin (/* height = */ box_height,
                                /* width = */ width,
-                               /* y = */ main_win_height + (5 * context->index),
+                               /* y = */ main_win_height + (box_height * context->index),
                                /* x = */ 0);
        }
 
@@ -838,6 +1156,7 @@ static int pre_loop_hook (pingobj_t *ping) /* {{{ */
        int width = 0;
        int height = 0;
        int main_win_height;
+       int box_height = (opt_show_graph == 0) ? 4 : 5;
 
        initscr ();
        cbreak ();
@@ -859,7 +1178,7 @@ static int pre_loop_hook (pingobj_t *ping) /* {{{ */
                init_pair (OPING_RED_HIST,    COLOR_RED,    COLOR_YELLOW);
        }
 
-       main_win_height = height - (5 * host_num);
+       main_win_height = height - (box_height * host_num);
        main_win = newwin (/* height = */ main_win_height,
                        /* width = */ width,
                        /* y = */ 0, /* x = */ 0);
@@ -886,9 +1205,9 @@ static int pre_loop_hook (pingobj_t *ping) /* {{{ */
                        delwin (context->window);
                        context->window = NULL;
                }
-               context->window = newwin (/* height = */ 5,
+               context->window = newwin (/* height = */ box_height,
                                /* width = */ width,
-                               /* y = */ main_win_height + (5 * context->index),
+                               /* y = */ main_win_height + (box_height * context->index),
                                /* x = */ 0);
        }
 
@@ -954,6 +1273,48 @@ static int post_sleep_hook (__attribute__((unused)) pingobj_t *ping) /* {{{ */
 } /* }}} int post_sleep_hook */
 #endif
 
+static size_t latency_to_bucket (ping_context_t *ctx, double latency) /* {{{ */
+{
+       size_t bucket;
+
+       /* latency is in ms, opt_interval is in s. */
+       bucket = (size_t) ((latency * (ctx->latency_histogram_size - 1))
+                       / (1000.0 * opt_interval));
+       if (bucket >= ctx->latency_histogram_size)
+               bucket = ctx->latency_histogram_size - 1;
+
+       return (bucket);
+} /* }}} size_t latency_to_bucket */
+
+static void update_context (ping_context_t *context, double latency) /* {{{ */
+{
+       size_t bucket;
+       size_t i;
+       double num;
+
+       context->req_rcvd++;
+       context->latency_total += latency;
+
+       if ((context->latency_max < 0.0) || (context->latency_max < latency))
+               context->latency_max = latency;
+       if ((context->latency_min < 0.0) || (context->latency_min > latency))
+               context->latency_min = latency;
+
+       bucket = latency_to_bucket (context, latency);
+       num = (double) context->req_rcvd;
+
+       context->histogram_counters[bucket]++;
+
+       context->histogram_accumulated[0] = context->histogram_counters[0];
+       context->histogram_ratio[0] = ((double) context->histogram_accumulated[0]) / num;
+       for (i = 1; i < context->latency_histogram_size; i++)
+       {
+               context->histogram_accumulated[i] = context->histogram_accumulated[i - 1]
+                       + context->histogram_counters[i];
+               context->histogram_ratio[i] = ((double) context->histogram_accumulated[i]) / num;
+       }
+} /* }}} void update_context */
+
 static void update_host_hook (pingobj_iter_t *iter, /* {{{ */
                __attribute__((unused)) int index)
 {
@@ -1001,28 +1362,33 @@ static void update_host_hook (pingobj_iter_t *iter, /* {{{ */
        context->req_sent++;
        if (latency > 0.0)
        {
-               context->req_rcvd++;
-               context->latency_total += latency;
-               context->latency_total_square += (latency * latency);
-
-               if ((context->latency_max < 0.0) || (context->latency_max < latency))
-                       context->latency_max = latency;
-               if ((context->latency_min < 0.0) || (context->latency_min > latency))
-                       context->latency_min = latency;
+               update_context (context, latency);
 
 #if USE_NCURSES
                if (has_colors () == TRUE)
                {
+                       size_t bucket;
+                       double ratio_this;
+                       double ratio_prev;
                        int color = OPING_GREEN;
-                       double average = context_get_average (context);
-                       double stddev = context_get_stddev (context);
 
-                       if ((latency < (average - (2 * stddev)))
-                                       || (latency > (average + (2 * stddev))))
-                               color = OPING_RED;
-                       else if ((latency < (average - stddev))
-                                       || (latency > (average + stddev)))
+                       bucket = latency_to_bucket (context, latency);
+                       ratio_this = context->histogram_ratio[bucket];
+                       if (bucket > 0)
+                               ratio_prev = context->histogram_ratio[bucket - 1];
+                       else
+                               ratio_prev = 0.0;
+
+                       if ((ratio_this <= threshold_green)
+                                       || ((ratio_prev < threshold_green)
+                                               && (ratio_this > threshold_green)))
+                               color = OPING_GREEN;
+                       else if ((ratio_this <= threshold_yellow)
+                                       || ((ratio_prev < threshold_yellow)
+                                               && (ratio_this > threshold_yellow)))
                                color = OPING_YELLOW;
+                       else
+                               color = OPING_RED;
 
                        HOST_PRINTF ("%zu bytes from %s (%s): icmp_seq=%u ttl=%i ",
                                        data_len, context->host, context->addr,
@@ -1056,7 +1422,7 @@ static void update_host_hook (pingobj_iter_t *iter, /* {{{ */
                }
 #endif
        }
-       else
+       else /* if (!(latency > 0.0)) */
        {
 #if USE_NCURSES
                if (has_colors () == TRUE)
@@ -1086,9 +1452,13 @@ static void update_host_hook (pingobj_iter_t *iter, /* {{{ */
 #endif
 } /* }}} void update_host_hook */
 
+/* Prints statistics for each host, cleans up the contexts and returns the
+ * number of hosts which failed to return more than the fraction
+ * opt_exit_status_threshold of pings. */
 static int post_loop_hook (pingobj_t *ping) /* {{{ */
 {
        pingobj_iter_t *iter;
+       int failure_count = 0;
 
 #if USE_NCURSES
        endwin ();
@@ -1108,26 +1478,32 @@ static int post_loop_hook (pingobj_t *ping) /* {{{ */
                                context_get_packet_loss (context),
                                context->latency_total);
 
+               {
+                       double pct_failed = 1.0 - (((double) context->req_rcvd)
+                                       / ((double) context->req_sent));
+                       if (pct_failed > opt_exit_status_threshold)
+                               failure_count++;
+               }
+
                if (context->req_rcvd != 0)
                {
-                       double average;
-                       double deviation;
+                       double median;
+                       double percentile;
 
-                       average = context_get_average (context);
-                       deviation = context_get_stddev (context);
+                       median = context_get_percentile (context, 50.0);
+                       percentile = context_get_percentile (context, opt_percentile);
 
-                       printf ("rtt min/avg/max/sdev = %.3f/%.3f/%.3f/%.3f ms\n",
-                                       context->latency_min,
-                                       average,
-                                       context->latency_max,
-                                       deviation);
+                       printf ("RTT[ms]: min = %.0f, median = %.0f, p(%.0f) = %.0f, max = %.0f\n",
+                                       context->latency_min, median,
+                                       opt_percentile, percentile,
+                                       context->latency_max);
                }
 
                ping_iterator_set_context (iter, NULL);
                context_destroy (context);
        }
 
-       return (0);
+       return (failure_count);
 } /* }}} int post_loop_hook */
 
 int main (int argc, char **argv) /* {{{ */
@@ -1336,6 +1712,9 @@ int main (int argc, char **argv) /* {{{ */
                exit (EXIT_FAILURE);
        }
 
+       if (host_num == 0)
+               exit (EXIT_FAILURE);
+
 #if _POSIX_SAVED_IDS
        saved_set_uid = (uid_t) -1;
 #endif
@@ -1366,7 +1745,12 @@ int main (int argc, char **argv) /* {{{ */
                        return (1);
                }
 
-               if (ping_send (ping) < 0)
+               status = ping_send (ping);
+               if (status == -EINTR)
+               {
+                       continue;
+               }
+               else if (status < 0)
                {
                        fprintf (stderr, "ping_send failed: %s\n",
                                        ping_get_error (ping));
@@ -1399,14 +1783,13 @@ int main (int argc, char **argv) /* {{{ */
                /* printf ("Sleeping for %i.%09li seconds\n", (int) ts_wait.tv_sec, ts_wait.tv_nsec); */
                while ((status = nanosleep (&ts_wait, &ts_wait)) != 0)
                {
-                       if (errno != EINTR)
+                       if (errno == EINTR)
                        {
-                               perror ("nanosleep");
-                               break;
+                               continue;
                        }
-                       else if (opt_count == 0)
+                       else
                        {
-                               /* sigint */
+                               perror ("nanosleep");
                                break;
                        }
                }
@@ -1417,11 +1800,19 @@ int main (int argc, char **argv) /* {{{ */
                        opt_count--;
        } /* while (opt_count != 0) */
 
-       post_loop_hook (ping);
+       /* Returns the number of failed hosts according to -Z. */
+       status = post_loop_hook (ping);
 
        ping_destroy (ping);
 
-       return (0);
+       if (status == 0)
+               exit (EXIT_SUCCESS);
+       else
+       {
+               if (status > 255)
+                       status = 255;
+               exit (status);
+       }
 } /* }}} int main */
 
 /* vim: set fdm=marker : */