ntpd: remove unused USING_INITIAL_FREQ_ESTIMATION code

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 2 insertions, 182 deletions

diff --git a/networking/ntpd.c b/networking/ntpd.c
index 8c9e59de1..62543ad2f 100644
--- a/networking/ntpd.c
+++ b/networking/ntpd.c
@@ -373,8 +373,7 @@ typedef struct {
 } peer_t;
 
 
-#define USING_KERNEL_PLL_LOOP          1
-#define USING_INITIAL_FREQ_ESTIMATION  0
+#define USING_KERNEL_PLL_LOOP 1
 
 enum {
         OPT_n = (1 << 0),
@@ -657,104 +656,11 @@ filter_datapoints(peer_t *p)
         double sum, wavg;
         datapoint_t *fdp;
 
-#if 0
 /* Simulations have shown that use of *averaged* offset for p->filter_offset
  * is in fact worse than simply using last received one: with large poll intervals
  * (>= 2048) averaging code uses offset values which are outdated by hours,
  * and time/frequency correction goes totally wrong when fed essentially bogus offsets.
  */
-        int got_newest;
-        double minoff, maxoff, w;
-        double x = x; /* for compiler */
-        double oldest_off = oldest_off;
-        double oldest_age = oldest_age;
-        double newest_off = newest_off;
-        double newest_age = newest_age;
-
-        fdp = p->filter_datapoint;
-
-        minoff = maxoff = fdp[0].d_offset;
-        for (i = 1; i < NUM_DATAPOINTS; i++) {
-                if (minoff > fdp[i].d_offset)
-                        minoff = fdp[i].d_offset;
-                if (maxoff < fdp[i].d_offset)
-                        maxoff = fdp[i].d_offset;
-        }
-
-        idx = p->datapoint_idx; /* most recent datapoint's index */
-        /* Average offset:
-         * Drop two outliers and take weighted average of the rest:
-         * most_recent/2 + older1/4 + older2/8 ... + older5/32 + older6/32
-         * we use older6/32, not older6/64 since sum of weights should be 1:
-         * 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/32 = 1
-         */
-        wavg = 0;
-        w = 0.5;
-        /*                     n-1
-         *                     ---    dispersion(i)
-         * filter_dispersion =  \     -------------
-         *                      /       (i+1)
-         *                     ---     2
-         *                     i=0
-         */
-        got_newest = 0;
-        sum = 0;
-        for (i = 0; i < NUM_DATAPOINTS; i++) {
-                VERB5 {
-                        bb_error_msg("datapoint[%d]: off:%f disp:%f(%f) age:%f%s",
-                                i,
-                                fdp[idx].d_offset,
-                                fdp[idx].d_dispersion, dispersion(&fdp[idx]),
-                                G.cur_time - fdp[idx].d_recv_time,
-                                (minoff == fdp[idx].d_offset || maxoff == fdp[idx].d_offset)
-                                        ? " (outlier by offset)" : ""
-                        );
-                }
-
-                sum += dispersion(&fdp[idx]) / (2 << i);
-
-                if (minoff == fdp[idx].d_offset) {
-                        minoff -= 1; /* so that we don't match it ever again */
-                } else
-                if (maxoff == fdp[idx].d_offset) {
-                        maxoff += 1;
-                } else {
-                        oldest_off = fdp[idx].d_offset;
-                        oldest_age = G.cur_time - fdp[idx].d_recv_time;
-                        if (!got_newest) {
-                                got_newest = 1;
-                                newest_off = oldest_off;
-                                newest_age = oldest_age;
-                        }
-                        x = oldest_off * w;
-                        wavg += x;
-                        w /= 2;
-                }
-
-                idx = (idx - 1) & (NUM_DATAPOINTS - 1);
-        }
-        p->filter_dispersion = sum;
-        wavg += x; /* add another older6/64 to form older6/32 */
-        /* Fix systematic underestimation with large poll intervals.
-         * Imagine that we still have a bit of uncorrected drift,
-         * and poll interval is big (say, 100 sec). Offsets form a progression:
-         * 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 - 0.7 is most recent.
-         * The algorithm above drops 0.0 and 0.7 as outliers,
-         * and then we have this estimation, ~25% off from 0.7:
-         * 0.1/32 + 0.2/32 + 0.3/16 + 0.4/8 + 0.5/4 + 0.6/2 = 0.503125
-         */
-        x = oldest_age - newest_age;
-        if (x != 0) {
-                x = newest_age / x; /* in above example, 100 / (600 - 100) */
-                if (x < 1) { /* paranoia check */
-                        x = (newest_off - oldest_off) * x; /* 0.5 * 100/500 = 0.1 */
-                        wavg += x;
-                }
-        }
-        p->filter_offset = wavg;
-
-#else
-
         fdp = p->filter_datapoint;
         idx = p->datapoint_idx; /* most recent datapoint's index */
 
@@ -777,7 +683,6 @@ filter_datapoints(peer_t *p)
         }
         wavg /= NUM_DATAPOINTS;
         p->filter_dispersion = sum;
-#endif
 
         /*                  +-----                 -----+ ^ 1/2
          *                  |       n-1                 |
@@ -1572,8 +1477,6 @@ update_local_clock(peer_t *p)
         double abs_offset;
 #if !USING_KERNEL_PLL_LOOP
         double freq_drift;
-#endif
-#if !USING_KERNEL_PLL_LOOP || USING_INITIAL_FREQ_ESTIMATION
         double since_last_update;
 #endif
         double etemp, dtemp;
@@ -1603,63 +1506,15 @@ update_local_clock(peer_t *p)
          * action is and defines how the system reacts to large time
          * and frequency errors.
          */
-#if !USING_KERNEL_PLL_LOOP || USING_INITIAL_FREQ_ESTIMATION
-        since_last_update = recv_time - G.reftime;
-#endif
 #if !USING_KERNEL_PLL_LOOP
+        since_last_update = recv_time - G.reftime;
         freq_drift = 0;
 #endif
-#if USING_INITIAL_FREQ_ESTIMATION
-        if (G.discipline_state == STATE_FREQ) {
-                /* Ignore updates until the stepout threshold */
-                if (since_last_update < WATCH_THRESHOLD) {
-                        VERB4 bb_error_msg("measuring drift, datapoint ignored, %f sec remains",
-                                        WATCH_THRESHOLD - since_last_update);
-                        return 0; /* "leave poll interval as is" */
-                }
-# if !USING_KERNEL_PLL_LOOP
-                freq_drift = (offset - G.last_update_offset) / since_last_update;
-# endif
-        }
-#endif
 
         /* There are two main regimes: when the
          * offset exceeds the step threshold and when it does not.
          */
         if (abs_offset > STEP_THRESHOLD) {
-#if 0
-                double remains;
-
-// This "spike state" seems to be useless, peer selection already drops
-// occassional "bad" datapoints. If we are here, there were _many_
-// large offsets. When a few first large offsets are seen,
-// we end up in "no valid datapoints, no peer selected" state.
-// Only when enough of them are seen (which means it's not a fluke),
-// we end up here. Looks like _our_ clock is off.
-                switch (G.discipline_state) {
-                case STATE_SYNC:
-                        /* The first outlyer: ignore it, switch to SPIK state */
-                        VERB3 bb_error_msg("update from %s: offset:%+f, spike%s",
-                                p->p_dotted, offset,
-                                "");
-                        G.discipline_state = STATE_SPIK;
-                        return -1; /* "decrease poll interval" */
-
-                case STATE_SPIK:
-                        /* Ignore succeeding outlyers until either an inlyer
-                         * is found or the stepout threshold is exceeded.
-                         */
-                        remains = WATCH_THRESHOLD - since_last_update;
-                        if (remains > 0) {
-                                VERB3 bb_error_msg("update from %s: offset:%+f, spike%s",
-                                        p->p_dotted, offset,
-                                        ", datapoint ignored");
-                                return -1; /* "decrease poll interval" */
-                        }
-                        /* fall through: we need to step */
-                } /* switch */
-#endif
-
                 /* Step the time and clamp down the poll interval.
                  *
                  * In NSET state an initial frequency correction is
@@ -1694,12 +1549,6 @@ update_local_clock(peer_t *p)
 
                 recv_time += offset;
 
-#if USING_INITIAL_FREQ_ESTIMATION
-                if (G.discipline_state == STATE_NSET) {
-                        set_new_values(STATE_FREQ, /*offset:*/ 0, recv_time);
-                        return 1; /* "ok to increase poll interval" */
-                }
-#endif
                 abs_offset = offset = 0;
                 set_new_values(STATE_SYNC, offset, recv_time);
         } else { /* abs_offset <= STEP_THRESHOLD */
@@ -1726,39 +1575,10 @@ update_local_clock(peer_t *p)
                                  */
                                 exit(0);
                         }
-#if USING_INITIAL_FREQ_ESTIMATION
-                        /* This is the first update received and the frequency
-                         * has not been initialized. The first thing to do
-                         * is directly measure the oscillator frequency.
-                         */
-                        set_new_values(STATE_FREQ, offset, recv_time);
-#else
                         set_new_values(STATE_SYNC, offset, recv_time);
-#endif
                         VERB4 bb_simple_error_msg("transitioning to FREQ, datapoint ignored");
                         return 0; /* "leave poll interval as is" */
 
-#if 0 /* this is dead code for now */
-                case STATE_FSET:
-                        /* This is the first update and the frequency
-                         * has been initialized. Adjust the phase, but
-                         * don't adjust the frequency until the next update.
-                         */
-                        set_new_values(STATE_SYNC, offset, recv_time);
-                        /* freq_drift remains 0 */
-                        break;
-#endif
-
-#if USING_INITIAL_FREQ_ESTIMATION
-                case STATE_FREQ:
-                        /* since_last_update >= WATCH_THRESHOLD, we waited enough.
-                         * Correct the phase and frequency and switch to SYNC state.
-                         * freq_drift was already estimated (see code above)
-                         */
-                        set_new_values(STATE_SYNC, offset, recv_time);
-                        break;
-#endif
-
                 default:
 #if !USING_KERNEL_PLL_LOOP
                         /* Compute freq_drift due to PLL and FLL contributions.