add simple schedule

rmatif · rmatif · commit 6f81e6bc0ce6 · 2025-05-07T18:59:22.000Z
diff --git a/denoiser.hpp b/denoiser.hpp
@@ -279,6 +279,48 @@ struct KarrasSchedule : SigmaSchedule {
     }
 };
 
+struct SimpleSchedule : SigmaSchedule {
+    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_sigmas;
+
+        if (n == 0) {
+            return result_sigmas; // Return empty for n=0, consistent with DiscreteSchedule
+        }
+
+        result_sigmas.reserve(n + 1);
+
+        // TIMESTEPS is the length of the model's internal sigmas array, typically 1000.
+        // t_to_sigma(t) maps a timestep t (0 to TIMESTEPS-1) to its sigma value.
+        int model_sigmas_len = TIMESTEPS; 
+
+        // ss = len(s.sigmas) / steps in Python
+        float step_factor = static_cast<float>(model_sigmas_len) / static_cast<float>(n);
+
+        for (uint32_t i = 0; i < n; ++i) {
+            // Python: s.sigmas[-(1 + int(x * ss))]
+            // x corresponds to i (0 to n-1)
+            // int(x * ss) in Python is static_cast<int>(static_cast<float>(i) * step_factor)
+            // The index -(1 + offset) means (model_sigmas_len - 1 - offset) from the start of a 0-indexed array.
+            int offset_from_start_of_py_array = static_cast<int>(static_cast<float>(i) * step_factor);
+            int timestep_index = model_sigmas_len - 1 - offset_from_start_of_py_array;
+
+            // Ensure the index is within valid bounds [0, model_sigmas_len - 1]
+            if (timestep_index < 0) {
+                timestep_index = 0;
+            }
+            // No need for upper bound check like `timestep_index >= model_sigmas_len` because
+            // max offset is for i=n-1: int((n-1)/n * model_sigmas_len) which is < model_sigmas_len.
+            // So, model_sigmas_len - 1 - max_offset is >= 0 if model_sigmas_len/n >= 1.
+            // If n > model_sigmas_len, then model_sigmas_len/n < 1, resulting in timestep_index potentially being <0,
+            // which is handled by the clamp above.
+
+            result_sigmas.push_back(t_to_sigma(static_cast<float>(timestep_index)));
+        }
+        result_sigmas.push_back(0.0f); // Append the final zero sigma
+        return result_sigmas;
+    }
+};
+
 struct Denoiser {
     std::shared_ptr<SigmaSchedule> schedule                                                  = std::make_shared<DiscreteSchedule>();
     virtual float sigma_min()                                                                = 0;
diff --git a/examples/cli/main.cpp b/examples/cli/main.cpp
@@ -52,6 +52,7 @@ const char* schedule_str[] = {
     "ays",
     "gits",
     "sgm_uniform",
+    "simple",
 };
 
 const char* modes_str[] = {
@@ -235,7 +236,7 @@ void print_usage(int argc, const char* argv[]) {
     printf("  --rng {std_default, cuda}          RNG (default: cuda)\n");
     printf("  -s SEED, --seed SEED               RNG seed (default: 42, use random seed for < 0)\n");
     printf("  -b, --batch-count COUNT            number of images to generate\n");
-    printf("  --schedule {discrete, karras, exponential, ays, gits, sgm_uniform} Denoiser sigma schedule (default: discrete)\n");
+    printf("  --schedule {discrete, karras, exponential, ays, gits, sgm_uniform, simple} Denoiser sigma schedule (default: discrete)\n");
     printf("  --clip-skip N                      ignore last layers of CLIP network; 1 ignores none, 2 ignores one layer (default: -1)\n");
     printf("                                     <= 0 represents unspecified, will be 1 for SD1.x, 2 for SD2.x\n");
     printf("  --vae-tiling                       process vae in tiles to reduce memory usage\n");
@@ -545,7 +546,7 @@ void parse_args(int argc, const char** argv, SDParams& params) {
                 }
             }
             if (schedule_found == -1) {
-                fprintf(stderr, "error: invalid schedule %s, must be one of [discrete, karras, exponential, ays, gits, sgm_uniform]\n", schedule_selected);
+                fprintf(stderr, "error: invalid schedule %s, must be one of [discrete, karras, exponential, ays, gits, sgm_uniform, simple]\n", schedule_selected);
                 exit(1); // Exit directly as invalid_arg only triggers at the end
             }
             params.schedule = (schedule_t)schedule_found;
diff --git a/stable-diffusion.cpp b/stable-diffusion.cpp
@@ -585,6 +585,11 @@ class StableDiffusionGGML {
                     denoiser->schedule          = std::make_shared<SGMUniformSchedule>();
                     denoiser->schedule->version = version; // version might not be used by SGMUniform but good to keep pattern
                     break;
+                case SIMPLE:
+                    LOG_INFO("Running with Simple schedule");
+                    denoiser->schedule          = std::make_shared<SimpleSchedule>();
+                    denoiser->schedule->version = version; // version might not be used by Simple but good to keep pattern
+                    break;                    
                 case DEFAULT:
                     // Don't touch anything.
                     break;
diff --git a/stable-diffusion.h b/stable-diffusion.h
@@ -57,6 +57,7 @@ enum schedule_t {
     AYS,
     GITS,
     SGM_UNIFORM,
+    SIMPLE,
     N_SCHEDULES
 };
 
