Beta Scheduler

phil2sat · Green-Sky · commit f382a48e5961 · 2025-09-10T12:03:34.000+02:00
diff --git a/denoiser.hpp b/denoiser.hpp
@@ -3,6 +3,7 @@
 
 #include "ggml_extend.hpp"
 #include "gits_noise.inl"
+#include <boost/math/distributions/beta.hpp>
 
 /*================================================= CompVisDenoiser ==================================================*/
 
@@ -251,6 +252,48 @@ struct KarrasSchedule : SigmaSchedule {
     }
 };
 
+struct BetaSchedule : SigmaSchedule {
+    float alpha = 0.6f;
+    float beta  = 0.6f;
+
+    BetaSchedule(float a = 0.6f, float b = 0.6f) : alpha(a), beta(b) {}
+
+    std::vector<float> get_sigmas(uint32_t n, float sigma_min, float sigma_max, t_to_sigma_t t_to_sigma) override {
+        std::vector<float> result;
+        result.reserve(n + 1);
+
+        int t_max = TIMESTEPS - 1;
+        if (n == 0) {
+            return result;
+        } else if (n == 1) {
+            result.push_back(t_to_sigma((float)t_max));
+            result.push_back(0);
+            return result;
+        }
+
+        // Beta-Verteilung (wie scipy.stats.beta.ppf)
+        boost::math::beta_distribution<double> dist(alpha, beta);
+
+        int last_t = -1;
+        for (uint32_t i = 0; i < n; i++) {
+            // entspricht ts = 1 - linspace(0,1,n,endpoint=False)
+            double u = 1.0 - static_cast<double>(i) / static_cast<double>(n);
+
+            // ppf(ts) * total_timesteps
+            double t_cont = quantile(dist, u) * t_max;
+            int t = (int)std::lround(t_cont);
+
+            if (t != last_t) {
+                result.push_back(t_to_sigma((float)t));
+                last_t = t;
+            }
+        }
+
+        result.push_back(0.0f);
+        return result;
+    }
+};
+
 struct Denoiser {
     std::shared_ptr<SigmaSchedule> scheduler                                                 = std::make_shared<DiscreteSchedule>();
     virtual float sigma_min()                                                                = 0;
diff --git a/examples/cli/main.cpp b/examples/cli/main.cpp
@@ -238,7 +238,7 @@ void print_usage(int argc, const char* argv[]) {
     printf("  --skip-layers LAYERS               Layers to skip for SLG steps: (default: [7,8,9])\n");
     printf("  --skip-layer-start START           SLG enabling point: (default: 0.01)\n");
     printf("  --skip-layer-end END               SLG disabling point: (default: 0.2)\n");
-    printf("  --scheduler {discrete, karras, exponential, ays, gits} Denoiser sigma scheduler (default: discrete)\n");
+    printf("  --scheduler {discrete, karras, beta, exponential, ays, gits} Denoiser sigma scheduler (default: discrete)\n");
     printf("  --sampling-method {euler, euler_a, heun, dpm2, dpm++2s_a, dpm++2m, dpm++2mv2, ipndm, ipndm_v, lcm, ddim_trailing, tcd}\n");
     printf("                                     sampling method (default: \"euler_a\")\n");
     printf("  --steps  STEPS                     number of sample steps (default: 20)\n");
@@ -251,7 +251,7 @@ void print_usage(int argc, const char* argv[]) {
     printf("  --high-noise-skip-layers LAYERS    (high noise) Layers to skip for SLG steps: (default: [7,8,9])\n");
     printf("  --high-noise-skip-layer-start      (high noise) SLG enabling point: (default: 0.01)\n");
     printf("  --high-noise-skip-layer-end END    (high noise) SLG disabling point: (default: 0.2)\n");
-    printf("  --high-noise-scheduler {discrete, karras, exponential, ays, gits} Denoiser sigma scheduler (default: discrete)\n");
+    printf("  --high-noise-scheduler {discrete, karras, beta, exponential, ays, gits} Denoiser sigma scheduler (default: discrete)\n");
     printf("  --high-noise-sampling-method {euler, euler_a, heun, dpm2, dpm++2s_a, dpm++2m, dpm++2mv2, ipndm, ipndm_v, lcm, ddim_trailing, tcd}\n");
     printf("                                     (high noise) sampling method (default: \"euler_a\")\n");
     printf("  --high-noise-steps  STEPS          (high noise) number of sample steps (default: -1 = auto)\n");
diff --git a/stable-diffusion.cpp b/stable-diffusion.cpp
@@ -730,6 +730,10 @@ class StableDiffusionGGML {
                 LOG_INFO("running with Karras scheduler");
                 denoiser->scheduler = std::make_shared<KarrasSchedule>();
                 break;
+            case BETA:
+                LOG_INFO("running with Beta scheduler");
+                denoiser->scheduler = std::make_shared<BetaSchedule>();
+                break;
             case EXPONENTIAL:
                 LOG_INFO("running exponential scheduler");
                 denoiser->scheduler = std::make_shared<ExponentialSchedule>();
@@ -1524,6 +1528,7 @@ const char* schedule_to_str[] = {
     "default",
     "discrete",
     "karras",
+    "beta",
     "exponential",
     "ays",
     "gits",
diff --git a/stable-diffusion.h b/stable-diffusion.h
@@ -54,6 +54,7 @@ enum scheduler_t {
     DEFAULT,
     DISCRETE,
     KARRAS,
+    BETA,
     EXPONENTIAL,
     AYS,
     GITS,
