feat: default to LCM scheduler for LCM sampling (#1109)

* feat: default to LCM scheduler for LCM sampling

* fix bug and attempt to get default scheduler for vid_gen when none is set

---------

Co-authored-by: leejet <leejet714@gmail.com>

Author: wbruna

examples/cli/main.cpp

@@ -579,7 +579,7 @@ int main(int argc, const char* argv[]) {
         }
 
         if (gen_params.sample_params.scheduler == SCHEDULER_COUNT) {
-            gen_params.sample_params.scheduler = sd_get_default_scheduler(sd_ctx);
+            gen_params.sample_params.scheduler = sd_get_default_scheduler(sd_ctx, gen_params.sample_params.sample_method);
         }
 
         if (cli_params.mode == IMG_GEN) {
@@ -752,4 +752,4 @@ int main(int argc, const char* argv[]) {
     release_all_resources();
 
     return 0;
-}
+}

stable-diffusion.cpp

@@ -2777,13 +2777,16 @@ enum sample_method_t sd_get_default_sample_method(const sd_ctx_t* sd_ctx) {
     return EULER_A_SAMPLE_METHOD;
 }
 
-enum scheduler_t sd_get_default_scheduler(const sd_ctx_t* sd_ctx) {
+enum scheduler_t sd_get_default_scheduler(const sd_ctx_t* sd_ctx, enum sample_method_t sample_method) {
     if (sd_ctx != nullptr && sd_ctx->sd != nullptr) {
         auto edm_v_denoiser = std::dynamic_pointer_cast<EDMVDenoiser>(sd_ctx->sd->denoiser);
         if (edm_v_denoiser) {
             return EXPONENTIAL_SCHEDULER;
         }
     }
+    if (sample_method == LCM_SAMPLE_METHOD) {
+        return LCM_SCHEDULER;
+    }
     return DISCRETE_SCHEDULER;
 }
 
@@ -3218,9 +3221,13 @@ sd_image_t* generate_image(sd_ctx_t* sd_ctx, const sd_img_gen_params_t* sd_img_g
             LOG_WARN("sample_steps != custom_sigmas_count - 1, set sample_steps to %d", sample_steps);
         }
     } else {
+        scheduler_t scheduler = sd_img_gen_params->sample_params.scheduler;
+        if (scheduler == SCHEDULER_COUNT) {
+            scheduler = sd_get_default_scheduler(sd_ctx, sample_method);
+        }
         sigmas = sd_ctx->sd->denoiser->get_sigmas(sample_steps,
                                                   sd_ctx->sd->get_image_seq_len(height, width),
-                                                  sd_img_gen_params->sample_params.scheduler,
+                                                  scheduler,
                                                   sd_ctx->sd->version);
     }
 
@@ -3503,9 +3510,13 @@ SD_API sd_image_t* generate_video(sd_ctx_t* sd_ctx, const sd_vid_gen_params_t* s
             }
         }
     } else {
+        scheduler_t scheduler = sd_vid_gen_params->sample_params.scheduler;
+        if (scheduler == SCHEDULER_COUNT) {
+            scheduler = sd_get_default_scheduler(sd_ctx, sample_method);
+        }
         sigmas = sd_ctx->sd->denoiser->get_sigmas(total_steps,
                                                   0,
-                                                  sd_vid_gen_params->sample_params.scheduler,
+                                                  scheduler,
                                                   sd_ctx->sd->version);
     }
 

stable-diffusion.h

@@ -335,7 +335,7 @@ SD_API void sd_sample_params_init(sd_sample_params_t* sample_params);
 SD_API char* sd_sample_params_to_str(const sd_sample_params_t* sample_params);
 
 SD_API enum sample_method_t sd_get_default_sample_method(const sd_ctx_t* sd_ctx);
-SD_API enum scheduler_t sd_get_default_scheduler(const sd_ctx_t* sd_ctx);
+SD_API enum scheduler_t sd_get_default_scheduler(const sd_ctx_t* sd_ctx, enum sample_method_t sample_method);
 
 SD_API void sd_img_gen_params_init(sd_img_gen_params_t* sd_img_gen_params);
 SD_API char* sd_img_gen_params_to_str(const sd_img_gen_params_t* sd_img_gen_params);