ntpd: drop offset averaging code
function old new delta filter_datapoints 475 174 -301 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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Denys Vlasenko
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4e3beb2e1d
commit
d98dc92d6a
@ -212,8 +212,8 @@ typedef struct {
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} msg_t;
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typedef struct {
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double d_recv_time;
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double d_offset;
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double d_recv_time;
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double d_dispersion;
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} datapoint_t;
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@ -517,23 +517,34 @@ static void
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filter_datapoints(peer_t *p)
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{
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int i, idx;
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double sum, wavg;
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datapoint_t *fdp;
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#if 0
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/* Simulations have shown that use of *averaged* offset for p->filter_offset
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* is in fact worse than simply using last received one: with large poll intervals
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* (>= 2048) averaging code uses offset values which are outdated by hours,
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* and time/frequency correction goes totally wrong when fed essentially bogus offsets.
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*/
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int got_newest;
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double minoff, maxoff, wavg, sum, w;
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double minoff, maxoff, w;
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double x = x; /* for compiler */
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double oldest_off = oldest_off;
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double oldest_age = oldest_age;
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double newest_off = newest_off;
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double newest_age = newest_age;
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minoff = maxoff = p->filter_datapoint[0].d_offset;
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fdp = p->filter_datapoint;
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minoff = maxoff = fdp[0].d_offset;
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for (i = 1; i < NUM_DATAPOINTS; i++) {
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if (minoff > p->filter_datapoint[i].d_offset)
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minoff = p->filter_datapoint[i].d_offset;
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if (maxoff < p->filter_datapoint[i].d_offset)
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maxoff = p->filter_datapoint[i].d_offset;
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if (minoff > fdp[i].d_offset)
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minoff = fdp[i].d_offset;
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if (maxoff < fdp[i].d_offset)
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maxoff = fdp[i].d_offset;
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}
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idx = p->datapoint_idx; /* most recent datapoint */
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idx = p->datapoint_idx; /* most recent datapoint's index */
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/* Average offset:
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* Drop two outliers and take weighted average of the rest:
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* most_recent/2 + older1/4 + older2/8 ... + older5/32 + older6/32
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@ -555,24 +566,24 @@ filter_datapoints(peer_t *p)
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VERB4 {
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bb_error_msg("datapoint[%d]: off:%f disp:%f(%f) age:%f%s",
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i,
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p->filter_datapoint[idx].d_offset,
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p->filter_datapoint[idx].d_dispersion, dispersion(&p->filter_datapoint[idx]),
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G.cur_time - p->filter_datapoint[idx].d_recv_time,
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(minoff == p->filter_datapoint[idx].d_offset || maxoff == p->filter_datapoint[idx].d_offset)
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fdp[idx].d_offset,
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fdp[idx].d_dispersion, dispersion(&fdp[idx]),
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G.cur_time - fdp[idx].d_recv_time,
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(minoff == fdp[idx].d_offset || maxoff == fdp[idx].d_offset)
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? " (outlier by offset)" : ""
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);
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}
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sum += dispersion(&p->filter_datapoint[idx]) / (2 << i);
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sum += dispersion(&fdp[idx]) / (2 << i);
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if (minoff == p->filter_datapoint[idx].d_offset) {
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if (minoff == fdp[idx].d_offset) {
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minoff -= 1; /* so that we don't match it ever again */
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} else
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if (maxoff == p->filter_datapoint[idx].d_offset) {
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if (maxoff == fdp[idx].d_offset) {
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maxoff += 1;
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} else {
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oldest_off = p->filter_datapoint[idx].d_offset;
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oldest_age = G.cur_time - p->filter_datapoint[idx].d_recv_time;
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oldest_off = fdp[idx].d_offset;
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oldest_age = G.cur_time - fdp[idx].d_recv_time;
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if (!got_newest) {
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got_newest = 1;
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newest_off = oldest_off;
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@ -605,6 +616,32 @@ filter_datapoints(peer_t *p)
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}
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p->filter_offset = wavg;
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#else
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fdp = p->filter_datapoint;
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idx = p->datapoint_idx; /* most recent datapoint's index */
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/* filter_offset: simply use the most recent value */
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p->filter_offset = fdp[idx].d_offset;
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/* n-1
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* --- dispersion(i)
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* filter_dispersion = \ -------------
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* / (i+1)
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* --- 2
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* i=0
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*/
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wavg = 0;
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sum = 0;
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for (i = 0; i < NUM_DATAPOINTS; i++) {
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sum += dispersion(&fdp[idx]) / (2 << i);
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wavg += fdp[idx].d_offset;
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idx = (idx - 1) & (NUM_DATAPOINTS - 1);
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}
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wavg /= NUM_DATAPOINTS;
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p->filter_dispersion = sum;
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#endif
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/* +----- -----+ ^ 1/2
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* | n-1 |
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* | --- |
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@ -618,13 +655,13 @@ filter_datapoints(peer_t *p)
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*/
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sum = 0;
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for (i = 0; i < NUM_DATAPOINTS; i++) {
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sum += SQUARE(wavg - p->filter_datapoint[i].d_offset);
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sum += SQUARE(wavg - fdp[i].d_offset);
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}
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sum = SQRT(sum / NUM_DATAPOINTS);
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p->filter_jitter = sum > G_precision_sec ? sum : G_precision_sec;
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VERB3 bb_error_msg("filter offset:%+f(corr:%e) disp:%f jitter:%f",
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p->filter_offset, x,
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VERB3 bb_error_msg("filter offset:%+f disp:%f jitter:%f",
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p->filter_offset,
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p->filter_dispersion,
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p->filter_jitter);
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}
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@ -1667,15 +1704,15 @@ recv_and_process_peer_pkt(peer_t *p)
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p->reachable_bits |= 1;
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if ((MAX_VERBOSE && G.verbose) || (option_mask32 & OPT_w)) {
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bb_error_msg("reply from:%s reach:0x%02x offset:%+f delay:%f status:0x%02x strat:%d refid:0x%08x rootdelay:%f",
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bb_error_msg("reply from:%s offset:%+f delay:%f status:0x%02x strat:%d refid:0x%08x rootdelay:%f reach:0x%02x",
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p->p_dotted,
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p->reachable_bits,
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datapoint->d_offset,
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p->lastpkt_delay,
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p->lastpkt_status,
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p->lastpkt_stratum,
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p->lastpkt_refid,
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p->lastpkt_rootdelay
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p->lastpkt_rootdelay,
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p->reachable_bits
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/* not shown: m_ppoll, m_precision_exp, m_rootdisp,
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* m_reftime, m_orgtime, m_rectime, m_xmttime
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*/
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