diff options
| author | Keith Packard <keithp@keithp.com> | 2012-06-27 19:45:22 -0700 |
|---|---|---|
| committer | Keith Packard <keithp@keithp.com> | 2012-06-27 19:45:22 -0700 |
| commit | 407cefae9cb95c5910b3bd79851776c48729e06b (patch) | |
| tree | cd48d89ff8c150e8929a140a122716bdcd76fb44 /src | |
| parent | 4f258fe565dc3e58b83761bfa1a2276946012163 (diff) | |
altos: Unroll viterbi state loop for >30% performance boost
9.3ms vs 14.7ms, a clear win.
Signed-off-by: Keith Packard <keithp@keithp.com>
Diffstat (limited to 'src')
| -rw-r--r-- | src/core/ao_fec_rx.c | 56 |
1 files changed, 34 insertions, 22 deletions
diff --git a/src/core/ao_fec_rx.c b/src/core/ao_fec_rx.c index d4c98475..c1a3918b 100644 --- a/src/core/ao_fec_rx.c +++ b/src/core/ao_fec_rx.c @@ -161,31 +161,43 @@ ao_fec_decode(const uint8_t *in, uint16_t len, uint8_t *out, uint8_t out_len, ui cost[n][state] = 0x7fffffff; /* Compute path costs and accumulate output bit path - * for each state and encoded bit value + * for each state and encoded bit value. Unrolling + * this loop is worth about > 30% performance boost. + * Decoding 76-byte remote access packets is reduced + * from 14.700ms to 9.3ms */ - for (state = 0; state < NUM_STATE; state++) { - uint32_t bitcost = ((uint32_t) (s0 ^ ao_fec_decode_table[(state<<1)]) + - (uint32_t) (s1 ^ ao_fec_decode_table[(state<<1)+1])); - { - uint32_t cost0 = cost[p][state] + bitcost; - uint8_t state0 = ao_next_state(state, 0); - - if (cost0 < cost[n][state0]) { - cost[n][state0] = cost0; - bits[n][state0] = (bits[p][state] << 1) | (state & 1); - } - } - { - uint32_t cost1 = cost[p][state] + 510 - bitcost; - uint8_t state1 = ao_next_state(state, 1); - - if (cost1 < cost[n][state1]) { - cost[n][state1] = cost1; - bits[n][state1] = (bits[p][state] << 1) | (state & 1); - } - } +#define DO_STATE(state) { \ + uint32_t bitcost = ((uint32_t) (s0 ^ ao_fec_decode_table[(state<<1)]) + \ + (uint32_t) (s1 ^ ao_fec_decode_table[(state<<1)+1])); \ + { \ + uint32_t cost0 = cost[p][state] + bitcost; \ + uint8_t state0 = ao_next_state(state, 0); \ + \ + if (cost0 < cost[n][state0]) { \ + cost[n][state0] = cost0; \ + bits[n][state0] = (bits[p][state] << 1) | (state & 1); \ + } \ + } \ + { \ + uint32_t cost1 = cost[p][state] + 510 - bitcost; \ + uint8_t state1 = ao_next_state(state, 1); \ + \ + if (cost1 < cost[n][state1]) { \ + cost[n][state1] = cost1; \ + bits[n][state1] = (bits[p][state] << 1) | (state & 1); \ + } \ + } \ } + DO_STATE(0); + DO_STATE(1); + DO_STATE(2); + DO_STATE(3); + DO_STATE(4); + DO_STATE(5); + DO_STATE(6); + DO_STATE(7); + #if 0 printf ("bit %3d symbol %2x %2x:", i/2, s0, s1); for (state = 0; state < NUM_STATE; state++) { |