feat: add code and doc for running SSD1B models

Author: akleine

model.cpp

@@ -1858,7 +1858,12 @@ SDVersion ModelLoader::get_sd_version() {
         if (is_ip2p) {
             return VERSION_SDXL_PIX2PIX;
         }
-        return VERSION_SDXL;
+        for (auto& tensor_storage : tensor_storages) {
+            if (tensor_storage.name.find("model.diffusion_model.middle_block.1") != std::string::npos) {
+                return VERSION_SDXL;      // found a missing tensor in SSD1B, so it is SDXL
+            }
+        }
+       	return VERSION_SDXL_SSD1B;
     }
 
     if (is_flux) {

model.h

@@ -28,6 +28,7 @@ enum SDVersion {
     VERSION_SDXL,
     VERSION_SDXL_INPAINT,
     VERSION_SDXL_PIX2PIX,
+    VERSION_SDXL_SSD1B,
     VERSION_SVD,
     VERSION_SD3,
     VERSION_FLUX,
@@ -56,7 +57,7 @@ static inline bool sd_version_is_sd2(SDVersion version) {
 }
 
 static inline bool sd_version_is_sdxl(SDVersion version) {
-    if (version == VERSION_SDXL || version == VERSION_SDXL_INPAINT || version == VERSION_SDXL_PIX2PIX) {
+    if (version == VERSION_SDXL || version == VERSION_SDXL_INPAINT || version == VERSION_SDXL_PIX2PIX || version == VERSION_SDXL_SSD1B) {
         return true;
     }
     return false;

stable-diffusion.cpp

@@ -58,6 +58,7 @@ const char* model_version_to_str[] = {
     "SDXL",
     "SDXL Inpaint",
     "SDXL Instruct-Pix2Pix",
+    "SDXL (SSD1B)",
     "SVD",
     "SD3.x",
     "Flux",

unet.hpp

@@ -270,10 +270,14 @@ class UnetModelBlock : public GGMLBlock {
                         n_head = ch / d_head;
                     }
                     std::string name = "input_blocks." + std::to_string(input_block_idx) + ".1";
+                    int td=transformer_depth[i];
+                    if (version == VERSION_SDXL_SSD1B) {
+                        if (i==2) td=4;
+                    }
                     blocks[name]     = std::shared_ptr<GGMLBlock>(get_attention_layer(ch,
                                                                                       n_head,
                                                                                       d_head,
-                                                                                      transformer_depth[i],
+                                                                                      td,
                                                                                       context_dim));
                 }
                 input_block_chans.push_back(ch);
@@ -296,13 +300,14 @@ class UnetModelBlock : public GGMLBlock {
             n_head = ch / d_head;
         }
         blocks["middle_block.0"] = std::shared_ptr<GGMLBlock>(get_resblock(ch, time_embed_dim, ch));
-        blocks["middle_block.1"] = std::shared_ptr<GGMLBlock>(get_attention_layer(ch,
-                                                                                  n_head,
-                                                                                  d_head,
-                                                                                  transformer_depth[transformer_depth.size() - 1],
-                                                                                  context_dim));
-        blocks["middle_block.2"] = std::shared_ptr<GGMLBlock>(get_resblock(ch, time_embed_dim, ch));
-
+        if (version != VERSION_SDXL_SSD1B) {
+            blocks["middle_block.1"] = std::shared_ptr<GGMLBlock>(get_attention_layer(ch,
+                                                                                      n_head,
+                                                                                      d_head,
+                                                                                      transformer_depth[transformer_depth.size() - 1],
+                                                                                      context_dim));
+            blocks["middle_block.2"] = std::shared_ptr<GGMLBlock>(get_resblock(ch, time_embed_dim, ch));
+        }
         // output_blocks
         int output_block_idx = 0;
         for (int i = (int)len_mults - 1; i >= 0; i--) {
@@ -324,7 +329,12 @@ class UnetModelBlock : public GGMLBlock {
                         n_head = ch / d_head;
                     }
                     std::string name = "output_blocks." + std::to_string(output_block_idx) + ".1";
-                    blocks[name]     = std::shared_ptr<GGMLBlock>(get_attention_layer(ch, n_head, d_head, transformer_depth[i], context_dim));
+                    int td = transformer_depth[i];
+                    if (version == VERSION_SDXL_SSD1B) {
+                        if (i==2 && (j==0 || j==1)) td=4;
+                        if (i==1 && (j==1 || j==2)) td=1;
+                    }                                              
+                    blocks[name]     = std::shared_ptr<GGMLBlock>(get_attention_layer(ch, n_head, d_head, td, context_dim));
 
                     up_sample_idx++;
                 }
@@ -478,9 +488,10 @@ class UnetModelBlock : public GGMLBlock {
 
         // middle_block
         h = resblock_forward("middle_block.0", ctx, h, emb, num_video_frames);                      // [N, 4*model_channels, h/8, w/8]
-        h = attention_layer_forward("middle_block.1", ctx, backend, h, context, num_video_frames);  // [N, 4*model_channels, h/8, w/8]
-        h = resblock_forward("middle_block.2", ctx, h, emb, num_video_frames);                      // [N, 4*model_channels, h/8, w/8]
-
+        if (version != VERSION_SDXL_SSD1B) {
+            h = attention_layer_forward("middle_block.1", ctx, backend, h, context, num_video_frames);  // [N, 4*model_channels, h/8, w/8]
+            h = resblock_forward("middle_block.2", ctx, h, emb, num_video_frames);                      // [N, 4*model_channels, h/8, w/8]
+        }
         if (controls.size() > 0) {
             auto cs = ggml_scale_inplace(ctx, controls[controls.size() - 1], control_strength);
             h       = ggml_add(ctx, h, cs);  // middle control