|
| 1 | +#include "reasoning-budget.h" |
| 2 | +#include "common.h" |
| 3 | +#include "unicode.h" |
| 4 | + |
| 5 | +#include "log.h" |
| 6 | + |
| 7 | +#include <cmath> |
| 8 | +#include <cstdint> |
| 9 | +#include <string> |
| 10 | +#include <vector> |
| 11 | + |
| 12 | +struct token_matcher { |
| 13 | + std::vector<llama_token> tokens; |
| 14 | + size_t pos = 0; |
| 15 | + |
| 16 | + bool advance(llama_token token) { |
| 17 | + if (tokens.empty()) { |
| 18 | + return false; |
| 19 | + } |
| 20 | + |
| 21 | + if (token == tokens[pos]) { |
| 22 | + pos++; |
| 23 | + if (pos >= tokens.size()) { |
| 24 | + pos = 0; |
| 25 | + return true; |
| 26 | + } |
| 27 | + } else { |
| 28 | + pos = 0; |
| 29 | + if (token == tokens[0]) { |
| 30 | + pos = 1; |
| 31 | + } |
| 32 | + } |
| 33 | + return false; |
| 34 | + } |
| 35 | + |
| 36 | + void reset() { pos = 0; } |
| 37 | +}; |
| 38 | + |
| 39 | +struct common_reasoning_budget_ctx { |
| 40 | + const llama_vocab * vocab; |
| 41 | + |
| 42 | + token_matcher start_matcher; |
| 43 | + token_matcher end_matcher; |
| 44 | + std::vector<llama_token> forced_tokens; |
| 45 | + |
| 46 | + int32_t budget; // maximum tokens in reasoning block |
| 47 | + int32_t remaining; // tokens remaining in budget |
| 48 | + |
| 49 | + common_reasoning_budget_state state; |
| 50 | + |
| 51 | + // for forcing |
| 52 | + size_t force_pos; // next position in forced_tokens to force |
| 53 | +}; |
| 54 | + |
| 55 | +static const char * common_reasoning_budget_name(const struct llama_sampler * /*smpl*/) { |
| 56 | + return "reasoning-budget"; |
| 57 | +} |
| 58 | + |
| 59 | +static void common_reasoning_budget_accept(struct llama_sampler * smpl, llama_token token) { |
| 60 | + auto * ctx = (common_reasoning_budget_ctx *) smpl->ctx; |
| 61 | + |
| 62 | + switch (ctx->state) { |
| 63 | + case REASONING_BUDGET_IDLE: |
| 64 | + { |
| 65 | + if (ctx->start_matcher.advance(token)) { |
| 66 | + ctx->state = REASONING_BUDGET_COUNTING; |
| 67 | + ctx->remaining = ctx->budget; |
| 68 | + LOG_INF("reasoning-budget: activated, budget=%d tokens\n", ctx->budget); |
| 69 | + |
| 70 | + if (ctx->remaining <= 0) { |
| 71 | + ctx->state = REASONING_BUDGET_FORCING; |
| 72 | + ctx->force_pos = 0; |
| 73 | + LOG_INF("reasoning-budget: budget=0, forcing immediately\n"); |
| 74 | + } |
| 75 | + } |
| 76 | + break; |
| 77 | + } |
| 78 | + case REASONING_BUDGET_COUNTING: |
| 79 | + case REASONING_BUDGET_WAITING_UTF8: |
| 80 | + { |
| 81 | + if (ctx->end_matcher.advance(token)) { |
| 82 | + ctx->state = REASONING_BUDGET_DONE; |
| 83 | + LOG_INF("reasoning-budget: deactivated (natural end)\n"); |
| 84 | + break; |
| 85 | + } |
| 86 | + |
| 87 | + bool utf8_complete = true; |
| 88 | + if (ctx->vocab != nullptr) { |
| 89 | + const std::string piece = common_token_to_piece(ctx->vocab, token, false); |
| 90 | + utf8_complete = common_utf8_is_complete(piece); |
| 91 | + } |
| 92 | + |
| 93 | + if (ctx->state == REASONING_BUDGET_WAITING_UTF8) { |
| 94 | + if (utf8_complete) { |
| 95 | + ctx->state = REASONING_BUDGET_FORCING; |
| 96 | + ctx->force_pos = 0; |
| 97 | + ctx->end_matcher.reset(); |
| 98 | + LOG_INF("reasoning-budget: UTF-8 complete, now forcing end sequence\n"); |
| 99 | + } |
| 100 | + } else if (ctx->state == REASONING_BUDGET_COUNTING) { |
| 101 | + ctx->remaining--; |
| 102 | + if (ctx->remaining <= 0) { |
| 103 | + if (utf8_complete) { |
| 104 | + ctx->state = REASONING_BUDGET_FORCING; |
| 105 | + ctx->force_pos = 0; |
| 106 | + ctx->end_matcher.reset(); |
| 107 | + LOG_INF("reasoning-budget: budget exhausted, forcing end sequence\n"); |
| 108 | + } else { |
| 109 | + ctx->state = REASONING_BUDGET_WAITING_UTF8; |
| 110 | + ctx->end_matcher.reset(); |
| 111 | + LOG_INF("reasoning-budget: budget exhausted, waiting for UTF-8 completion\n"); |
| 112 | + } |
| 113 | + } |
| 114 | + } |
| 115 | + break; |
| 116 | + } |
| 117 | + case REASONING_BUDGET_FORCING: |
| 118 | + // force_pos is advanced in apply(), not here. |
| 119 | + // This ensures the first forced token isn't skipped when the sampler |
| 120 | + // is initialized directly in FORCING state (e.g. COUNTING + budget=0) |
| 121 | + break; |
| 122 | + case REASONING_BUDGET_DONE: |
| 123 | + break; |
| 124 | + } |
| 125 | +} |
| 126 | + |
| 127 | +static void common_reasoning_budget_apply(struct llama_sampler * smpl, llama_token_data_array * cur_p) { |
| 128 | + auto * ctx = (common_reasoning_budget_ctx *) smpl->ctx; |
| 129 | + |
| 130 | + if (ctx->state != REASONING_BUDGET_FORCING) { |
| 131 | + // passthrough — don't modify logits |
| 132 | + return; |
| 133 | + } |
| 134 | + |
| 135 | + if (ctx->force_pos >= ctx->forced_tokens.size()) { |
| 136 | + return; |
| 137 | + } |
| 138 | + |
| 139 | + const llama_token forced = ctx->forced_tokens[ctx->force_pos]; |
| 140 | + |
| 141 | + // set all logits to -inf except the forced token |
| 142 | + for (size_t i = 0; i < cur_p->size; i++) { |
| 143 | + if (cur_p->data[i].id != forced) { |
| 144 | + cur_p->data[i].logit = -INFINITY; |
| 145 | + } |
| 146 | + } |
| 147 | + |
| 148 | + // advance to next forced token (done here rather than in accept so that |
| 149 | + // the first forced token isn't skipped when starting in FORCING state) |
| 150 | + ctx->force_pos++; |
| 151 | + if (ctx->force_pos >= ctx->forced_tokens.size()) { |
| 152 | + ctx->state = REASONING_BUDGET_DONE; |
| 153 | + LOG_INF("reasoning-budget: forced sequence complete, done\n"); |
| 154 | + } |
| 155 | +} |
| 156 | + |
| 157 | +static void common_reasoning_budget_reset(struct llama_sampler * smpl) { |
| 158 | + auto * ctx = (common_reasoning_budget_ctx *) smpl->ctx; |
| 159 | + ctx->state = REASONING_BUDGET_IDLE; |
| 160 | + ctx->remaining = ctx->budget; |
| 161 | + ctx->start_matcher.reset(); |
| 162 | + ctx->end_matcher.reset(); |
| 163 | + ctx->force_pos = 0; |
| 164 | +} |
| 165 | + |
| 166 | +static struct llama_sampler * common_reasoning_budget_clone(const struct llama_sampler * smpl) { |
| 167 | + const auto * ctx = (const common_reasoning_budget_ctx *) smpl->ctx; |
| 168 | + return common_reasoning_budget_init( |
| 169 | + ctx->vocab, |
| 170 | + ctx->start_matcher.tokens, |
| 171 | + ctx->end_matcher.tokens, |
| 172 | + ctx->forced_tokens, |
| 173 | + ctx->budget, |
| 174 | + ctx->state); |
| 175 | +} |
| 176 | + |
| 177 | +static void common_reasoning_budget_free(struct llama_sampler * smpl) { |
| 178 | + delete (common_reasoning_budget_ctx *) smpl->ctx; |
| 179 | +} |
| 180 | + |
| 181 | +static struct llama_sampler_i common_reasoning_budget_i = { |
| 182 | + /* .name = */ common_reasoning_budget_name, |
| 183 | + /* .accept = */ common_reasoning_budget_accept, |
| 184 | + /* .apply = */ common_reasoning_budget_apply, |
| 185 | + /* .reset = */ common_reasoning_budget_reset, |
| 186 | + /* .clone = */ common_reasoning_budget_clone, |
| 187 | + /* .free = */ common_reasoning_budget_free, |
| 188 | + /* .backend_init = */ nullptr, |
| 189 | + /* .backend_accept = */ nullptr, |
| 190 | + /* .backend_apply = */ nullptr, |
| 191 | + /* .backend_set_input = */ nullptr, |
| 192 | +}; |
| 193 | + |
| 194 | +struct llama_sampler * common_reasoning_budget_init( |
| 195 | + const struct llama_vocab * vocab, |
| 196 | + const std::vector<llama_token> & start_tokens, |
| 197 | + const std::vector<llama_token> & end_tokens, |
| 198 | + const std::vector<llama_token> & forced_tokens, |
| 199 | + int32_t budget, |
| 200 | + common_reasoning_budget_state initial_state) { |
| 201 | + // promote COUNTING with budget <= 0 to FORCING |
| 202 | + if (initial_state == REASONING_BUDGET_COUNTING && budget <= 0) { |
| 203 | + initial_state = REASONING_BUDGET_FORCING; |
| 204 | + } |
| 205 | + |
| 206 | + return llama_sampler_init( |
| 207 | + /* .iface = */ &common_reasoning_budget_i, |
| 208 | + /* .ctx = */ new common_reasoning_budget_ctx { |
| 209 | + /* .vocab = */ vocab, |
| 210 | + /* .start_matcher = */ { start_tokens, 0 }, |
| 211 | + /* .end_matcher = */ { end_tokens, 0 }, |
| 212 | + /* .forced_tokens = */ forced_tokens, |
| 213 | + /* .budget = */ budget, |
| 214 | + /* .remaining = */ budget, |
| 215 | + /* .state = */ initial_state, |
| 216 | + /* .force_pos = */ 0, |
| 217 | + } |
| 218 | + ); |
| 219 | +} |
0 commit comments