revised power law sampling

Author: LostRuins

gpttype_adapter.cpp

@@ -1291,9 +1291,11 @@ llama_token_data_array * cur_p)
     float computed_target = std::clamp(total_weight == 0.0f ? target : 2.0f * target - (weighted_sum / total_weight),0.0f, 1.0f);
 
     // power law transform
+    const float k = 4.0f; // controls sharpness
     for (size_t i = 0; i < cur_p->size; ++i) {
         float dist = (cur_p->data[i].p - computed_target) * inv_width;
-        cur_p->data[i].logit = (peak_logit / (1.0f + dist * dist));
+        float abs_dist = fabs(dist);
+        cur_p->data[i].logit = peak_logit - k * abs_dist * (abs_dist / (1.0f + abs_dist));
     }
 
     cur_p->sorted = false;