feat: support for SDXS-512 model (#1180)

* feat: add U-Net specials of SDXS

* docs: update distilled_sd.md for SDXS-512

* feat: for SDXS use AutoencoderTiny as the primary VAE

* docs: update distilled_sd.md for SDXS-512

* fix: SDXS code cleaning after review by stduhpf

* format code

* fix sdxs with --taesd-preview-only

---------

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

docs/distilled_sd.md

@@ -83,7 +83,7 @@ python convert_diffusers_to_original_stable_diffusion.py \
 The file segmind_tiny-sd.ckpt will be generated and is now ready for use with sd.cpp. You can follow a similar process for the other models mentioned above.
 
 
-### Another available .ckpt file:
+##### Another available .ckpt file:
 
  * https://huggingface.co/ClashSAN/small-sd/resolve/main/tinySDdistilled.ckpt
 
@@ -97,3 +97,31 @@ for key, value in ckpt['state_dict'].items():
         ckpt['state_dict'][key] = value.contiguous()
 torch.save(ckpt, "tinySDdistilled_fixed.ckpt")
 ```
+
+
+### SDXS-512
+
+Another very tiny and **incredibly fast**  model is SDXS by IDKiro et al.  The authors refer to it as *"Real-Time One-Step Latent Diffusion Models with Image Conditions"*. For details read the paper: https://arxiv.org/pdf/2403.16627 . Once again the authors removed some more blocks of U-Net part and unlike other SD1 models they use an adjusted _AutoEncoderTiny_ instead of default _AutoEncoderKL_ for the VAE part.
+
+##### 1. Download the diffusers model from  Hugging Face using Python:
+
+```python
+from diffusers import StableDiffusionPipeline
+pipe = StableDiffusionPipeline.from_pretrained("IDKiro/sdxs-512-dreamshaper")
+pipe.save_pretrained(save_directory="sdxs")
+```
+##### 2. Create a safetensors file
+
+```bash
+python convert_diffusers_to_original_stable_diffusion.py \
+    --model_path  sdxs  --checkpoint_path sdxs.safetensors --half --use_safetensors
+```
+
+##### 3. Run the model as follows:
+
+```bash
+~/stable-diffusion.cpp/build/bin/sd-cli -m sdxs.safetensors -p "portrait of a lovely cat" \
+  --cfg-scale 1 --steps 1
+```
+
+Both options: ``` --cfg-scale 1 ``` and  ``` --steps 1 ``` are mandatory here.                                                 

model.cpp

@@ -1038,6 +1038,7 @@ SDVersion ModelLoader::get_sd_version() {
     int64_t patch_embedding_channels = 0;
     bool has_img_emb                 = false;
     bool has_middle_block_1          = false;
+    bool has_output_block_71         = false;
 
     for (auto& [name, tensor_storage] : tensor_storage_map) {
         if (!(is_xl)) {
@@ -1094,6 +1095,9 @@ SDVersion ModelLoader::get_sd_version() {
             tensor_storage.name.find("unet.mid_block.resnets.1.") != std::string::npos) {
             has_middle_block_1 = true;
         }
+        if (tensor_storage.name.find("model.diffusion_model.output_blocks.7.1") != std::string::npos) {
+            has_output_block_71 = true;
+        }
         if (tensor_storage.name == "cond_stage_model.transformer.text_model.embeddings.token_embedding.weight" ||
             tensor_storage.name == "cond_stage_model.model.token_embedding.weight" ||
             tensor_storage.name == "text_model.embeddings.token_embedding.weight" ||
@@ -1155,6 +1159,9 @@ SDVersion ModelLoader::get_sd_version() {
             return VERSION_SD1_PIX2PIX;
         }
         if (!has_middle_block_1) {
+            if (!has_output_block_71) {
+                return VERSION_SDXS;
+            }
             return VERSION_SD1_TINY_UNET;
         }
         return VERSION_SD1;

model.h

@@ -28,6 +28,7 @@ enum SDVersion {
     VERSION_SD2,
     VERSION_SD2_INPAINT,
     VERSION_SD2_TINY_UNET,
+    VERSION_SDXS,
     VERSION_SDXL,
     VERSION_SDXL_INPAINT,
     VERSION_SDXL_PIX2PIX,
@@ -50,7 +51,7 @@ enum SDVersion {
 };
 
 static inline bool sd_version_is_sd1(SDVersion version) {
-    if (version == VERSION_SD1 || version == VERSION_SD1_INPAINT || version == VERSION_SD1_PIX2PIX || version == VERSION_SD1_TINY_UNET) {
+    if (version == VERSION_SD1 || version == VERSION_SD1_INPAINT || version == VERSION_SD1_PIX2PIX || version == VERSION_SD1_TINY_UNET || version == VERSION_SDXS) {
         return true;
     }
     return false;

stable-diffusion.cpp

@@ -31,6 +31,7 @@ const char* model_version_to_str[] = {
     "SD 2.x",
     "SD 2.x Inpaint",
     "SD 2.x Tiny UNet",
+    "SDXS",
     "SDXL",
     "SDXL Inpaint",
     "SDXL Instruct-Pix2Pix",
@@ -407,6 +408,11 @@ public:
             vae_decode_only = false;
         }
 
+        bool tae_preview_only = sd_ctx_params->tae_preview_only;
+        if (version == VERSION_SDXS) {
+            tae_preview_only = false;
+        }
+
         if (sd_ctx_params->circular_x || sd_ctx_params->circular_y) {
             LOG_INFO("Using circular padding for convolutions");
         }
@@ -591,7 +597,7 @@ public:
                 vae_backend = backend;
             }
 
-            if (!use_tiny_autoencoder || sd_ctx_params->tae_preview_only) {
+            if (!(use_tiny_autoencoder || version == VERSION_SDXS) || tae_preview_only) {
                 if (sd_version_is_wan(version) || sd_version_is_qwen_image(version)) {
                     first_stage_model = std::make_shared<WAN::WanVAERunner>(vae_backend,
                                                                             offload_params_to_cpu,
@@ -629,8 +635,7 @@ public:
                     first_stage_model->get_param_tensors(tensors, "first_stage_model");
                 }
             }
-
-            if (use_tiny_autoencoder) {
+            if (use_tiny_autoencoder || version == VERSION_SDXS) {
                 if (sd_version_is_wan(version) || sd_version_is_qwen_image(version)) {
                     tae_first_stage = std::make_shared<TinyVideoAutoEncoder>(vae_backend,
                                                                              offload_params_to_cpu,
@@ -645,6 +650,10 @@ public:
                                                                              "decoder.layers",
                                                                              vae_decode_only,
                                                                              version);
+                    if (version == VERSION_SDXS) {
+                        tae_first_stage->alloc_params_buffer();
+                        tae_first_stage->get_param_tensors(tensors, "first_stage_model");
+                    }
                 }
                 if (sd_ctx_params->vae_conv_direct) {
                     LOG_INFO("Using Conv2d direct in the tae model");
@@ -782,14 +791,15 @@ public:
                 unet_params_mem_size += high_noise_diffusion_model->get_params_buffer_size();
             }
             size_t vae_params_mem_size = 0;
-            if (!use_tiny_autoencoder || sd_ctx_params->tae_preview_only) {
+            if (!(use_tiny_autoencoder || version == VERSION_SDXS) || tae_preview_only) {
                 vae_params_mem_size = first_stage_model->get_params_buffer_size();
             }
-            if (use_tiny_autoencoder) {
-                if (!tae_first_stage->load_from_file(taesd_path, n_threads)) {
+            if (use_tiny_autoencoder || version == VERSION_SDXS) {
+                if (use_tiny_autoencoder && !tae_first_stage->load_from_file(taesd_path, n_threads)) {
                     return false;
                 }
-                vae_params_mem_size = tae_first_stage->get_params_buffer_size();
+                use_tiny_autoencoder = true;  // now the processing is identical for VERSION_SDXS
+                vae_params_mem_size  = tae_first_stage->get_params_buffer_size();
             }
             size_t control_net_params_mem_size = 0;
             if (control_net) {
@@ -945,7 +955,7 @@ public:
         }
 
         ggml_free(ctx);
-        use_tiny_autoencoder = use_tiny_autoencoder && !sd_ctx_params->tae_preview_only;
+        use_tiny_autoencoder = use_tiny_autoencoder && !tae_preview_only;
         return true;
     }
 

tae.hpp

@@ -505,7 +505,8 @@ struct TinyAutoEncoder : public GGMLRunner {
                          struct ggml_tensor** output,
                          struct ggml_context* output_ctx = nullptr) = 0;
 
-    virtual bool load_from_file(const std::string& file_path, int n_threads) = 0;
+    virtual bool load_from_file(const std::string& file_path, int n_threads)                                      = 0;
+    virtual void get_param_tensors(std::map<std::string, struct ggml_tensor*>& tensors, const std::string prefix) = 0;
 };
 
 struct TinyImageAutoEncoder : public TinyAutoEncoder {
@@ -555,6 +556,10 @@ struct TinyImageAutoEncoder : public TinyAutoEncoder {
         return success;
     }
 
+    void get_param_tensors(std::map<std::string, struct ggml_tensor*>& tensors, const std::string prefix) {
+        taesd.get_param_tensors(tensors, prefix);
+    }
+
     struct ggml_cgraph* build_graph(struct ggml_tensor* z, bool decode_graph) {
         struct ggml_cgraph* gf  = ggml_new_graph(compute_ctx);
         z                       = to_backend(z);
@@ -624,6 +629,10 @@ struct TinyVideoAutoEncoder : public TinyAutoEncoder {
         return success;
     }
 
+    void get_param_tensors(std::map<std::string, struct ggml_tensor*>& tensors, const std::string prefix) {
+        taehv.get_param_tensors(tensors, prefix);
+    }
+
     struct ggml_cgraph* build_graph(struct ggml_tensor* z, bool decode_graph) {
         struct ggml_cgraph* gf  = ggml_new_graph(compute_ctx);
         z                       = to_backend(z);

unet.hpp

@@ -215,10 +215,13 @@ public:
         } else if (sd_version_is_unet_edit(version)) {
             in_channels = 8;
         }
-        if (version == VERSION_SD1_TINY_UNET || version == VERSION_SD2_TINY_UNET) {
+        if (version == VERSION_SD1_TINY_UNET || version == VERSION_SD2_TINY_UNET || version == VERSION_SDXS) {
             num_res_blocks = 1;
             channel_mult   = {1, 2, 4};
             tiny_unet      = true;
+            if (version == VERSION_SDXS) {
+                attention_resolutions = {4, 2};  // here just like SDXL
+            }
         }
 
         // dims is always 2