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stepcompreses: Change the step queue to use 32bit integers 

The RaspberryPi processor implements 'double to int32' conversions
much faster than 'double to int64' conversions.  Rework the code so
that steps stored in the queue are always a small offset from the last
sent step time.  (In the unlikely event that a step is far from the
last step time, then the queue is flushed to maintain this invariant.)

This simplifies the step compression code as well - it no longer needs
to check for integer overflows.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2017-08-30 12:42:53 -04:00
parent f5cc355044
commit e05c635489
1 changed files with 57 additions and 37 deletions
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88
klippy/stepcompress.c
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@ -28,7 +28,7 @@
struct stepcompress {
// Buffer management
uint64_t *queue, *queue_end, *queue_pos, *queue_next;
uint32_t *queue, *queue_end, *queue_pos, *queue_next;
// Internal tracking
uint32_t max_error;
// Message generation
@ -64,10 +64,11 @@ struct points {
// Given a requested step time, return the minimum and maximum
// acceptable times
static inline struct points
minmax_point(struct stepcompress *sc, uint64_t *pos)
minmax_point(struct stepcompress *sc, uint32_t *pos)
{
uint32_t prevpoint = pos > sc->queue_pos ? *(pos-1) - sc->last_step_clock : 0;
uint32_t point = *pos - sc->last_step_clock;
uint32_t lsc = sc->last_step_clock;
uint32_t prevpoint = pos > sc->queue_pos ? *(pos-1) - lsc : 0;
uint32_t point = *pos - lsc;
uint32_t max_error = (point - prevpoint) / 2;
if (max_error > sc->max_error)
max_error = sc->max_error;
@ -90,6 +91,9 @@ struct step_move {
static struct step_move
compress_bisect_add(struct stepcompress *sc)
{
uint32_t *qlast = sc->queue_next;
if (qlast > sc->queue_pos + 65535)
qlast = sc->queue_pos + 65535;
struct points point = minmax_point(sc, sc->queue_pos);
int32_t outer_mininterval = point.minp, outer_maxinterval = point.maxp;
int32_t add = 0, minadd = -0x8000, maxadd = 0x7fff;
@ -104,10 +108,7 @@ compress_bisect_add(struct stepcompress *sc)
int32_t nextcount = 1;
for (;;) {
nextcount++;
if (nextcount > bestcount
&& (&sc->queue_pos[nextcount-1] >= sc->queue_next
|| sc->queue_pos[nextcount-1] >= sc->last_step_clock+(3<<28)
|| nextcount > 65535)) {
if (&sc->queue_pos[nextcount-1] >= qlast) {
int32_t count = nextcount - 1;
return (struct step_move){ interval, count, add };
}
@ -194,18 +195,7 @@ check_line(struct stepcompress *sc, struct step_move move)
{
if (!CHECK_LINES)
return 0;
if (move.count == 1) {
if (move.interval != (uint32_t)(*sc->queue_pos - sc->last_step_clock)
|| *sc->queue_pos < sc->last_step_clock) {
errorf("stepcompress o=%d i=%d c=%d a=%d:"
" Count 1 point out of range (%lld)"
, sc->oid, move.interval, move.count, move.add
, (long long)(*sc->queue_pos - sc->last_step_clock));
return ERROR_RET;
}
return 0;
}
if (!move.count || (!move.interval && !move.add)
if (!move.count || (!move.interval && !move.add && move.count > 1)
|| move.interval >= 0x80000000) {
errorf("stepcompress o=%d i=%d c=%d a=%d: Invalid sequence"
, sc->oid, move.interval, move.count, move.add);
@ -274,7 +264,7 @@ stepcompress_flush(struct stepcompress *sc, uint64_t move_clock)
{
if (sc->queue_pos >= sc->queue_next)
return 0;
while (move_clock > sc->last_step_clock) {
while (sc->last_step_clock < move_clock) {
struct step_move move = compress_bisect_add(sc);
int ret = check_line(sc, move);
if (ret)
@ -285,14 +275,9 @@ stepcompress_flush(struct stepcompress *sc, uint64_t move_clock)
};
struct queue_message *qm = message_alloc_and_encode(msg, 5);
qm->min_clock = qm->req_clock = sc->last_step_clock;
if (move.count == 1 && sc->last_step_clock + (1<<27) < *sc->queue_pos) {
// Be careful with 32bit overflow
sc->last_step_clock = qm->req_clock = *sc->queue_pos;
} else {
int32_t addfactor = move.count*(move.count-1)/2;
uint32_t ticks = move.add*addfactor + move.interval*move.count;
sc->last_step_clock += ticks;
}
if (sc->homing_clock)
// When homing, all steps should be sent prior to homing_clock
qm->min_clock = qm->req_clock = sc->homing_clock;
@ -307,6 +292,23 @@ stepcompress_flush(struct stepcompress *sc, uint64_t move_clock)
return 0;
}
// Generate a queue_step for a step far in the future from the last step
static int
stepcompress_flush_far(struct stepcompress *sc, uint64_t abs_step_clock)
{
uint32_t msg[5] = {
sc->queue_step_msgid, sc->oid, abs_step_clock - sc->last_step_clock, 1, 0
};
struct queue_message *qm = message_alloc_and_encode(msg, 5);
qm->min_clock = sc->last_step_clock;
sc->last_step_clock = qm->req_clock = abs_step_clock;
if (sc->homing_clock)
// When homing, all steps should be sent prior to homing_clock
qm->min_clock = qm->req_clock = sc->homing_clock;
list_add_tail(&qm->node, &sc->msg_queue);
return 0;
}
// Send the set_next_step_dir command
static int
set_next_step_dir(struct stepcompress *sc, int sdir)
@ -370,17 +372,21 @@ stepcompress_queue_msg(struct stepcompress *sc, uint32_t *data, int len)
struct queue_append {
struct stepcompress *sc;
uint64_t *qnext, *qend;
uint32_t *qnext, *qend, last_step_clock_32;
double clock_offset;
};
// Maximium clock delta between messages in the queue
#define CLOCK_DIFF_MAX (3<<28)
// Create a cursor for inserting clock times into the queue
static inline struct queue_append
queue_append_start(struct stepcompress *sc, double clock_offset, double adjust)
{
return (struct queue_append) {
.sc = sc, .qnext = sc->queue_next, .qend = sc->queue_end,
.clock_offset = clock_offset + adjust };
.last_step_clock_32 = sc->last_step_clock,
.clock_offset = (clock_offset - (double)sc->last_step_clock) + adjust };
}
// Finalize a cursor created with queue_append_start()
@ -392,8 +398,19 @@ queue_append_finish(struct queue_append qa)
// Slow path for queue_append()
static int
queue_append_slow(struct stepcompress *sc, double abs_step_clock)
queue_append_slow(struct stepcompress *sc, double rel_sc)
{
uint64_t abs_step_clock = (uint64_t)rel_sc + sc->last_step_clock;
if (abs_step_clock >= sc->last_step_clock + CLOCK_DIFF_MAX) {
// Avoid integer overflow on steps far in the future
int ret = stepcompress_flush(sc, abs_step_clock - CLOCK_DIFF_MAX + 1);
if (ret)
return ret;
if (abs_step_clock >= sc->last_step_clock + CLOCK_DIFF_MAX)
return stepcompress_flush_far(sc, abs_step_clock);
}
if (sc->queue_next - sc->queue_pos > 65535 + 2000) {
// No point in keeping more than 64K steps in memory
int ret = stepcompress_flush(sc, *(sc->queue_next - 65535));
@ -425,19 +442,22 @@ queue_append_slow(struct stepcompress *sc, double abs_step_clock)
static inline int
queue_append(struct queue_append *qa, double step_clock)
{
double abs_step_clock = step_clock + qa->clock_offset;
if (likely(qa->qnext < qa->qend)) {
*qa->qnext++ = abs_step_clock;
double rel_sc = step_clock + qa->clock_offset;
if (likely(qa->qnext < qa->qend && rel_sc < (double)CLOCK_DIFF_MAX)) {
*qa->qnext++ = qa->last_step_clock_32 + (uint32_t)rel_sc;
return 0;
}
// Call queue_append_slow() to handle queue expansion
// Call queue_append_slow() to handle queue expansion and integer overflow
struct stepcompress *sc = qa->sc;
uint64_t old_last_step_clock = sc->last_step_clock;
sc->queue_next = qa->qnext;
int ret = queue_append_slow(sc, abs_step_clock);
int ret = queue_append_slow(sc, rel_sc);
if (ret)
return ret;
qa->qnext = sc->queue_next;
qa->qend = sc->queue_end;
qa->last_step_clock_32 = sc->last_step_clock;
qa->clock_offset -= sc->last_step_clock - old_last_step_clock;
return 0;
}