common : support manually triggering the reasoning budget end sequence (#23949)

common/reasoning-budget.cpp

@@ -247,3 +247,24 @@ common_reasoning_budget_state common_reasoning_budget_get_state(const struct lla
     }
     return ((const common_reasoning_budget_ctx *)smpl->ctx)->state;
 }
+
+bool common_reasoning_budget_force(struct llama_sampler * smpl) {
+    if (!smpl) {
+        return false;
+    }
+
+    auto * ctx = (common_reasoning_budget_ctx *) smpl->ctx;
+
+    // only a sampler that is actively counting down the budget may be forced;
+    // any other state (idle, already forcing/waiting, or done) is left untouched
+    if (ctx->state != REASONING_BUDGET_COUNTING) {
+        return false;
+    }
+
+    ctx->state = REASONING_BUDGET_FORCING;
+    ctx->force_pos = 0;
+    ctx->end_matcher.reset();
+    LOG_INF("reasoning-budget: forced into forcing state (manual transition)\n");
+
+    return true;
+}

common/reasoning-budget.h

@@ -40,3 +40,7 @@ struct llama_sampler * common_reasoning_budget_init(
         common_reasoning_budget_state    initial_state = REASONING_BUDGET_IDLE);
 
 common_reasoning_budget_state common_reasoning_budget_get_state(const struct llama_sampler * smpl);
+
+// Manually transition the reasoning budget sampler into the FORCING state.
+// Returns true if the transition occurred.
+bool common_reasoning_budget_force(struct llama_sampler * smpl);

common/sampling.cpp

@@ -661,6 +661,14 @@ uint32_t common_sampler_get_seed(const struct common_sampler * gsmpl) {
     return llama_sampler_get_seed(gsmpl->chain);
 }
 
+bool common_sampler_reasoning_budget_force(struct common_sampler * gsmpl) {
+    if (!gsmpl) {
+        return false;
+    }
+
+    return common_reasoning_budget_force(gsmpl->rbudget);
+}
+
 // helpers
 
 llama_token_data_array * common_sampler_get_candidates(struct common_sampler * gsmpl, bool do_sort) {

common/sampling.h

@@ -87,6 +87,9 @@ std::vector<llama_token> common_sampler_sample_and_accept_n(struct common_sample
 
 uint32_t common_sampler_get_seed(const struct common_sampler * gsmpl);
 
+// force the reasoning budget sampler (if any) to begin forcing its end sequence now.
+bool common_sampler_reasoning_budget_force(struct common_sampler * gsmpl);
+
 // helpers
 
 // access the internal list of current candidate tokens

tests/test-reasoning-budget.cpp

@@ -184,6 +184,76 @@ static void test_reasoning_budget_clone_mid_forcing() {
     llama_sampler_free(sampler);
 }
 
+static void test_reasoning_budget_force_manual() {
+    const std::vector<llama_token> start  = {100};
+    const std::vector<llama_token> end    = {101};
+    const std::vector<llama_token> forced = {102, 101};
+
+    // if COUNTING, force() succeeds and begins forcing the end sequence from the start
+    {
+        auto * sampler = common_reasoning_budget_init(nullptr, start, end, forced, 5, REASONING_BUDGET_IDLE);
+
+        llama_sampler_accept(sampler, 100); // COUNTING, remaining=5
+        llama_sampler_accept(sampler, 50);  // COUNTING, remaining=4
+        GGML_ASSERT(common_reasoning_budget_get_state(sampler) == REASONING_BUDGET_COUNTING);
+
+        GGML_ASSERT(common_reasoning_budget_force(sampler) && "force() should succeed from COUNTING");
+        GGML_ASSERT(common_reasoning_budget_get_state(sampler) == REASONING_BUDGET_FORCING);
+
+        // forces the configured sequence from force_pos=0, then transitions to DONE
+        GGML_ASSERT(get_forced_token(sampler, 102) == 102);
+        llama_sampler_accept(sampler, 102);
+        GGML_ASSERT(get_forced_token(sampler, 102) == 101);
+        llama_sampler_accept(sampler, 101);
+        GGML_ASSERT(common_reasoning_budget_get_state(sampler) == REASONING_BUDGET_DONE);
+
+        llama_sampler_free(sampler);
+    }
+
+    // if IDLE, force() is a no-op
+    {
+        auto * sampler = common_reasoning_budget_init(nullptr, start, end, forced, 5, REASONING_BUDGET_IDLE);
+
+        GGML_ASSERT(!common_reasoning_budget_force(sampler) && "force() must not transition from IDLE");
+        GGML_ASSERT(common_reasoning_budget_get_state(sampler) == REASONING_BUDGET_IDLE);
+
+        llama_sampler_free(sampler);
+    }
+
+    // if DONE, force() is a no-op
+    {
+        auto * sampler = common_reasoning_budget_init(nullptr, start, end, forced, 5, REASONING_BUDGET_IDLE);
+
+        llama_sampler_accept(sampler, 100); // COUNTING
+        llama_sampler_accept(sampler, 101); // natural end -> DONE
+        GGML_ASSERT(common_reasoning_budget_get_state(sampler) == REASONING_BUDGET_DONE);
+
+        GGML_ASSERT(!common_reasoning_budget_force(sampler) && "force() must not transition from DONE");
+        GGML_ASSERT(common_reasoning_budget_get_state(sampler) == REASONING_BUDGET_DONE);
+
+        llama_sampler_free(sampler);
+    }
+
+    // if FORCING, force() is a no-op and must not rewind the force position
+    {
+        auto * sampler = common_reasoning_budget_init(nullptr, start, end, forced, 0, REASONING_BUDGET_FORCING);
+
+        GGML_ASSERT(get_forced_token(sampler, 102) == 102);
+        llama_sampler_accept(sampler, 102); // advance to the second forced token (force_pos=1)
+
+        GGML_ASSERT(!common_reasoning_budget_force(sampler) && "force() must not transition from FORCING");
+        GGML_ASSERT(common_reasoning_budget_get_state(sampler) == REASONING_BUDGET_FORCING);
+        GGML_ASSERT(get_forced_token(sampler, 102) == 101 && "force() must not rewind the force position");
+
+        llama_sampler_free(sampler);
+    }
+
+    // a null sampler is safely ignored
+    GGML_ASSERT(!common_reasoning_budget_force(nullptr));
+
+    fprintf(stderr, "  Test 'manual force transition' passed\n");
+}
+
 // UTF-8 boundary detection unit test
 // Tests common_utf8_is_complete() from reasoning-budget.h
 static void test_utf8_boundary_detection() {
@@ -312,8 +382,9 @@ int main(void) {
 
     test_reasoning_budget_clone_mid_counting();
     test_reasoning_budget_clone_mid_forcing();
+    test_reasoning_budget_force_manual();
 
-    printf("OK (8 tests passed)\n");
+    printf("OK (9 tests passed)\n");
 
     printf("Testing UTF-8 boundary detection... ");
     test_utf8_boundary_detection();