add euler flow flash sample method

include/stable-diffusion.h

@@ -37,6 +37,7 @@ enum rng_type_t {
 
 enum sample_method_t {
     EULER_SAMPLE_METHOD,
+    EULER_FLOW_FLASH_SAMPLE_METHOD,
     EULER_A_SAMPLE_METHOD,
     HEUN_SAMPLE_METHOD,
     DPM2_SAMPLE_METHOD,

src/denoiser.hpp

@@ -867,6 +867,31 @@ static sd::Tensor<float> sample_euler_flow(denoise_cb_t model,
     return x;
 }
 
+static sd::Tensor<float> sample_euler_flow_flash(denoise_cb_t model,
+                                                 sd::Tensor<float> x,
+                                                 const std::vector<float>& sigmas,
+                                                 std::shared_ptr<RNG> rng,
+                                                 float eta) {
+    float s_noise = eta;
+    int steps     = static_cast<int>(sigmas.size()) - 1;
+    for (int i = 0; i < steps; i++) {
+        float sigma       = sigmas[i];
+        float sigma_next  = sigmas[i + 1];
+        auto denoised_opt = model(x, sigma, i + 1);
+        if (denoised_opt.empty()) {
+            return {};
+        }
+        sd::Tensor<float> denoised = std::move(denoised_opt);
+        if (sigma_next == 0.0f) {
+            x = std::move(denoised);
+            continue;
+        }
+        auto noise = sd::Tensor<float>::randn_like(x, rng);
+        x          = sigma_next * noise * s_noise + (1.0f - sigma_next) * denoised;
+    }
+    return x;
+}
+
 static sd::Tensor<float> sample_euler(denoise_cb_t model,
                                       sd::Tensor<float> x,
                                       const std::vector<float>& sigmas) {
@@ -1658,6 +1683,8 @@ static sd::Tensor<float> sample_k_diffusion(sample_method_t method,
                                             float eta,
                                             bool is_flow_denoiser) {
     switch (method) {
+        case EULER_FLOW_FLASH_SAMPLE_METHOD:
+            return sample_euler_flow_flash(model, std::move(x), sigmas, rng, eta);
         case EULER_A_SAMPLE_METHOD:
             if (is_flow_denoiser)
                 return sample_euler_flow(model, std::move(x), sigmas, rng, eta);

src/stable-diffusion.cpp

@@ -60,6 +60,7 @@ const char* model_version_to_str[] = {
 
 const char* sampling_methods_str[] = {
     "Euler",
+    "Euler Flow Flash",
     "Euler A",
     "Heun",
     "DPM2",
@@ -1978,6 +1979,7 @@ enum rng_type_t str_to_rng_type(const char* str) {
 
 const char* sample_method_to_str[] = {
     "euler",
+    "euler_flow_flash",
     "euler_a",
     "heun",
     "dpm2",