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Diffstat (limited to 'src/viterbi_generic.c')
| -rw-r--r-- | src/viterbi_generic.c | 207 |
1 files changed, 207 insertions, 0 deletions
diff --git a/src/viterbi_generic.c b/src/viterbi_generic.c new file mode 100644 index 00000000..2ced6152 --- /dev/null +++ b/src/viterbi_generic.c @@ -0,0 +1,207 @@ +/* + * Viterbi decoder + * + * Copyright (C) 2013, 2014 Thomas Tsou <tom@tsou.cc> + * + * All Rights Reserved + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#include <stdlib.h> +#include <stdint.h> +#include <string.h> + +/* Add-Compare-Select (ACS-Butterfly) + * Compute 4 accumulated path metrics and 4 path selections. Note that path + * selections are store as -1 and 0 rather than 0 and 1. This is to match + * the output format of the SSE packed compare instruction 'pmaxuw'. + */ + +static void acs_butterfly(int state, int num_states, + int16_t metric, int16_t *sum, + int16_t *new_sum, int16_t *path) +{ + int state0, state1; + int sum0, sum1, sum2, sum3; + + state0 = *(sum + (2 * state + 0)); + state1 = *(sum + (2 * state + 1)); + + sum0 = state0 + metric; + sum1 = state1 - metric; + sum2 = state0 - metric; + sum3 = state1 + metric; + + if (sum0 >= sum1) { + *new_sum = sum0; + *path = -1; + } else { + *new_sum = sum1; + *path = 0; + } + + if (sum2 >= sum3) { + *(new_sum + num_states / 2) = sum2; + *(path + num_states / 2) = -1; + } else { + *(new_sum + num_states / 2) = sum3; + *(path + num_states / 2) = 0; + } +} + +/* Branch metrics unit N=2 */ +static void gen_branch_metrics_n2(int num_states, const int8_t *seq, + const int16_t *out, int16_t *metrics) +{ + int i; + + for (i = 0; i < num_states / 2; i++) { + metrics[i] = seq[0] * out[2 * i + 0] + + seq[1] * out[2 * i + 1]; + } +} + +/* Branch metrics unit N=3 */ +static void gen_branch_metrics_n3(int num_states, const int8_t *seq, + const int16_t *out, int16_t *metrics) +{ + int i; + + for (i = 0; i < num_states / 2; i++) { + metrics[i] = seq[0] * out[4 * i + 0] + + seq[1] * out[4 * i + 1] + + seq[2] * out[4 * i + 2]; + } +} + +/* Branch metrics unit N=4 */ +static void gen_branch_metrics_n4(int num_states, const int8_t *seq, + const int16_t *out, int16_t *metrics) +{ + int i; + + for (i = 0; i < num_states / 2; i++) { + metrics[i] = seq[0] * out[4 * i + 0] + + seq[1] * out[4 * i + 1] + + seq[2] * out[4 * i + 2] + + seq[3] * out[4 * i + 3]; + } +} + +/* Path metric unit */ +static void gen_path_metrics(int num_states, int16_t *sums, + int16_t *metrics, int16_t *paths, int norm) +{ + int i; + int16_t min; + int16_t new_sums[num_states]; + + for (i = 0; i < num_states / 2; i++) + acs_butterfly(i, num_states, metrics[i], + sums, &new_sums[i], &paths[i]); + + if (norm) { + min = new_sums[0]; + + for (i = 1; i < num_states; i++) + if (new_sums[i] < min) + min = new_sums[i]; + + for (i = 0; i < num_states; i++) + new_sums[i] -= min; + } + + memcpy(sums, new_sums, num_states * sizeof(int16_t)); +} + +/* Not-aligned Memory Allocator */ +__attribute__ ((visibility("hidden"))) +int16_t *osmo_conv_vdec_malloc(size_t n) +{ + return (int16_t *) malloc(sizeof(int16_t) * n); +} + +__attribute__ ((visibility("hidden"))) +void osmo_conv_vdec_free(int16_t *ptr) +{ + free(ptr); +} + +/* 16-state branch-path metrics units (K=5) */ +__attribute__ ((visibility("hidden"))) +void osmo_conv_gen_metrics_k5_n2(const int8_t *seq, const int16_t *out, + int16_t *sums, int16_t *paths, int norm) +{ + int16_t metrics[8]; + + gen_branch_metrics_n2(16, seq, out, metrics); + gen_path_metrics(16, sums, metrics, paths, norm); +} + +__attribute__ ((visibility("hidden"))) +void osmo_conv_gen_metrics_k5_n3(const int8_t *seq, const int16_t *out, + int16_t *sums, int16_t *paths, int norm) +{ + int16_t metrics[8]; + + gen_branch_metrics_n3(16, seq, out, metrics); + gen_path_metrics(16, sums, metrics, paths, norm); + +} + +__attribute__ ((visibility("hidden"))) +void osmo_conv_gen_metrics_k5_n4(const int8_t *seq, const int16_t *out, + int16_t *sums, int16_t *paths, int norm) +{ + int16_t metrics[8]; + + gen_branch_metrics_n4(16, seq, out, metrics); + gen_path_metrics(16, sums, metrics, paths, norm); + +} + +/* 64-state branch-path metrics units (K=7) */ +__attribute__ ((visibility("hidden"))) +void osmo_conv_gen_metrics_k7_n2(const int8_t *seq, const int16_t *out, + int16_t *sums, int16_t *paths, int norm) +{ + int16_t metrics[32]; + + gen_branch_metrics_n2(64, seq, out, metrics); + gen_path_metrics(64, sums, metrics, paths, norm); + +} + +__attribute__ ((visibility("hidden"))) +void osmo_conv_gen_metrics_k7_n3(const int8_t *seq, const int16_t *out, + int16_t *sums, int16_t *paths, int norm) +{ + int16_t metrics[32]; + + gen_branch_metrics_n3(64, seq, out, metrics); + gen_path_metrics(64, sums, metrics, paths, norm); + +} + +__attribute__ ((visibility("hidden"))) +void osmo_conv_gen_metrics_k7_n4(const int8_t *seq, const int16_t *out, + int16_t *sums, int16_t *paths, int norm) +{ + int16_t metrics[32]; + + gen_branch_metrics_n4(64, seq, out, metrics); + gen_path_metrics(64, sums, metrics, paths, norm); +} |