On Wed, 10 Apr 2002, Hrvoje Niksic wrote:
> "Roger L. Beeman" <[EMAIL PROTECTED]> writes:
>
> > On Wed, 10 Apr 2002, Hrvoje Niksic wrote:
> >
> >> Agreed wholeheartedly, but how would you *implement* a non-jittering
> >> ETA? Do you think it makes sense the way 1.8.1 does it, i.e. to
> >> calculate the ETA from the average speed?
> >
> > One common programming technique is the exponential decay model.
>
> Sounds cool. Do you have a pseudocode or, failing that, a reference
> easy enough that even a programmer of Unix command-line utilities can
> follow it? :-)
>
> (I must admit that your email address adds a certain weight to
> whatever you have to say about measuring bandwidth.)
>
> > I believe that the method is chosen for its simplicity and that
> > justifications of its validity are completely after the fact. The
> > simplicity is that one keeps a previously calculated value and
> > averages that value with the current measurement and saves the
> > result for the next iteration, i.e. add and shift right.
>
> I thought about calculating the average between the "average" and the
> "current" speed, and use that for ETA, but it sounded too arbitrary
> and I didn't have time to gather empirical evidence that it was any
> better than just using average. Again, I'd be grateful if you could
> provide some code.
>
> > You must chose how to normalize the measurement based on
> > irregularity in the measurement interval, however.
>
> I'm afraid I can't parse this without understanding the algorithm.
Here is some code to illustrate my suggestion. I am posting
here rather than on wget-patches since it is only for that purpose.
An exponential decay model is implemented *only* for the bar mode.
Since math.h is included for the pow function, I had to add -lm
to the link libs in Makefile.
-------- patch against wget 1.8.1+cvs 15-04-2002 --------
--- src/progress.c.orig Tue Apr 16 13:19:06 2002
+++ src/progress.c Tue Apr 16 13:31:17 2002
@@ -21,6 +21,7 @@
#include <stdio.h>
#include <stdlib.h>
+#include <math.h>
#ifdef HAVE_STRING_H
# include <string.h>
#else
@@ -401,6 +402,9 @@
create_image will overflow the buffer. */
#define MINIMUM_SCREEN_WIDTH 45
+#define RATE_INTERVAL 1000 /* 1000mSec */
+#define DECAY_EXPN 2 /* Exponent */
+
static int screen_width = DEFAULT_SCREEN_WIDTH;
/* Size of the history table for download speeds. */
@@ -432,6 +436,8 @@
progress bar where the total size
is not known. */
+ double rate_decay; /* saved rate for exponential decay */
+ long last_dlcount; /* to calculate accumulated dl bytes */
/* The following variables (kept in a struct for namespace reasons)
keep track of recent download speeds. See bar_update() for
details. */
@@ -468,6 +474,8 @@
bp->initial_length = initial;
bp->total_length = total;
+ bp->count = 0;
+ bp->last_screen_update = 0;
/* - 1 because we don't want to use the last screen column. */
bp->width = screen_width - 1;
@@ -488,7 +496,7 @@
struct bar_progress *bp = progress;
struct bar_progress_hist *hist = &bp->hist;
int force_screen_update = 0;
- long delta_time = dltime - hist->previous_time;
+/* long delta_time = dltime - hist->previous_time; */
bp->count += howmuch;
if (bp->total_length > 0
@@ -507,6 +515,7 @@
"read" consists of one or more network reads, up until the point
where a subinterval is filled. */
+#if 0
if (hist->times[hist->pos]
>= DLSPEED_HISTORY_MAX_INTERVAL / DLSPEED_HISTORY_SIZE)
{
@@ -532,6 +541,7 @@
hist->summed_times += delta_time;
hist->summed_bytes += howmuch;
hist->previous_time = dltime;
+#endif
#if 0
/* Sledgehammer check that summed_times and summed_bytes are
@@ -563,6 +573,7 @@
create_image (bp, dltime);
display_image (bp->buffer);
bp->last_screen_update = dltime;
+ bp->last_dlcount = bp->count;
}
static void
@@ -593,6 +604,32 @@
# define MAX(a, b) ((a) >= (b) ? (a) : (b))
#endif
+/* Trim the download rate as appropriate for the speed. Appropriate
+ means that if rate is greater than 1K/s, kilobytes are used, and
+ if rate is greater than 1MB/s, megabytes are used.
+
+ UNITS is zero for B/s, one for KB/s, two for MB/s, and three for
+ GB/s. */
+double
+trim_rate (double raw_rate, int *units)
+{
+ double dlrate;
+
+ dlrate = raw_rate * 1000;
+ if (dlrate < 1024.0)
+ *units = 0;
+ else if (dlrate < 1024.0 * 1024.0)
+ *units = 1, dlrate /= 1024.0;
+ else if (dlrate < 1024.0 * 1024.0 * 1024.0)
+ *units = 2, dlrate /= (1024.0 * 1024.0);
+ else
+ /* Maybe someone will need this one day. More realistically, it
+ will get tickled by buggy timers. */
+ *units = 3, dlrate /= (1024.0 * 1024.0 * 1024.0);
+
+ return dlrate;
+}
+
static void
create_image (struct bar_progress *bp, long dl_total_time)
{
@@ -625,6 +662,14 @@
int dlbytes_size = 1 + MAX (size_legible_len, 11);
int progress_size = bp->width - (4 + 2 + dlbytes_size + 11 + 13);
+ long this_dlinterval;
+ double this_dlrate;
+ double ddlrate;
+ double decay_int;
+ double decay_factor;
+ static char *short_units[] = { "B/s", "K/s", "M/s", "G/s" };
+ int units = 0;
+
if (progress_size < 5)
progress_size = 0;
@@ -701,6 +746,7 @@
p += strlen (p);
/* " 1012.45K/s" */
+#if 0
if (hist->summed_times && hist->summed_bytes)
{
static char *short_units[] = { "B/s", "K/s", "M/s", "G/s" };
@@ -712,13 +758,43 @@
}
else
APPEND_LITERAL (" --.--K/s");
+#endif
+ if (dl_total_time && bp->count)
+ {
+ if (bp->last_screen_update < RATE_INTERVAL)
+ {
+ ddlrate = calc_rate (bp->count, dl_total_time, &units);
+ bp->rate_decay = (double) bp->count / dl_total_time;
+ }
+ else
+ {
+ this_dlinterval = dl_total_time - bp->last_screen_update;
+ this_dlrate = (double) (bp->count - bp->last_dlcount)
+ / this_dlinterval;
+ decay_int = -((double) this_dlinterval / RATE_INTERVAL);
+ decay_factor = pow (DECAY_EXPN, decay_int);
+ bp->rate_decay = ( (bp->rate_decay - this_dlrate) *
+ pow (DECAY_EXPN, decay_int) ) +
+ this_dlrate;
+ ddlrate = trim_rate (bp->rate_decay, &units);
+ }
+ sprintf (p, " %7.2f%s", ddlrate, short_units[units]);
+ p += strlen (p);
+ }
+ else
+ APPEND_LITERAL (" --.--K/s");
+
+
/* " ETA xx:xx:xx" */
- if (bp->total_length > 0 && dl_total_time > 3000)
+/* if (bp->total_length > 0 && dl_total_time > 3000) */
+ if (bp->total_length > 0 && bp->count > 0)
{
long eta;
int eta_hrs, eta_min, eta_sec;
+ long bytes_remaining = bp->total_length - size;
+#if 0
/* Don't change the value of ETA more than approximately once
per second; doing so would cause flashing without providing
any value to the user. */
@@ -739,7 +815,9 @@
bp->last_eta_value = eta;
bp->last_eta_time = dl_total_time;
}
+#endif
+ eta = MAX (0,(int) (bytes_remaining / (bp->rate_decay * 1000)));
eta_hrs = eta / 3600, eta %= 3600;
eta_min = eta / 60, eta %= 60;
eta_sec = eta;
-------- end patch --------
Roger L. Beeman
