model-conversion : add support for SentenceTransformers (#16387)

* model-conversion : add support for SentenceTransformers

This commit adds support for models that use SentenceTransformer layers.

The motivation for this is that if converted model includes any of the
numbered layers specified in the original models repository then these
changes enable these models to be used and verified. Currently the
model-conversion only support the base model output without any of
the additional transformation layers.

Usage:
Convert the model that also includes the SentenceTransformer layers:
```console
(venv) $ export EMBEDDING_MODEL_PATH="~/google/embeddinggemma-300M"
(venv) make embedding-convert-model
```

Verify the produced embeddings from the converted model against the
original model embeddings:
```console
(venv) make embedding-verify-logits-st
```

The original model can be run using SentenceTransformer:
```console
(venv) make embedding-run-original-model-st
```

Run the converted model using "SentenceTransformer" layers whic
enables pooling and normalization:
```console
(venv) make embedding-run-converted-model-st
```

* add model-conversion example requirements

* add support for -st flag in embedding model conversion

This commit add support for the -st flag in the embedding model
conversion script. This will enable models to be converted using
sentence transformers dense layers.

examples/model-conversion/logits.cpp

@@ -1,4 +1,7 @@
 #include "llama.h"
+#include "common.h"
+
+
 #include <cstdio>
 #include <cstring>
 #include <string>
@@ -8,7 +11,10 @@
 
 static void print_usage(int, char ** argv) {
     printf("\nexample usage:\n");
-    printf("\n    %s -m model.gguf [-ngl n_gpu_layers] -embd-mode [prompt]\n", argv[0]);
+    printf("\n    %s -m model.gguf [-ngl n_gpu_layers] -embd-mode [-pooling] [-embd-norm <norm>] [prompt]\n", argv[0]);
+    printf("\n");
+    printf("  -embd-norm: normalization type for pooled embeddings (default: 2)\n");
+    printf("              -1=none, 0=max absolute int16, 1=taxicab, 2=Euclidean/L2, >2=p-norm\n");
     printf("\n");
 }
 
@@ -17,6 +23,8 @@ int main(int argc, char ** argv) {
     std::string prompt = "Hello, my name is";
     int ngl = 0;
     bool embedding_mode = false;
+    bool pooling_enabled = false;
+    int32_t embd_norm = 2;  // (-1=none, 0=max absolute int16, 1=taxicab, 2=Euclidean/L2, >2=p-norm)
 
     {
         int i = 1;
@@ -41,9 +49,13 @@ int main(int argc, char ** argv) {
                     return 1;
                 }
             } else if (strcmp(argv[i], "-embd-mode") == 0) {
+                embedding_mode = true;
+            } else if (strcmp(argv[i], "-pooling") == 0) {
+                pooling_enabled = true;
+            } else if (strcmp(argv[i], "-embd-norm") == 0) {
                 if (i + 1 < argc) {
                     try {
-                        embedding_mode = true;
+                        embd_norm = std::stoi(argv[++i]);
                     } catch (...) {
                         print_usage(argc, argv);
                         return 1;
@@ -112,7 +124,7 @@ int main(int argc, char ** argv) {
     ctx_params.no_perf = false;
     if (embedding_mode) {
         ctx_params.embeddings = true;
-        ctx_params.pooling_type = LLAMA_POOLING_TYPE_NONE;
+        ctx_params.pooling_type = pooling_enabled ? LLAMA_POOLING_TYPE_MEAN : LLAMA_POOLING_TYPE_NONE;
         ctx_params.n_ubatch = ctx_params.n_batch;
     }
 
@@ -143,17 +155,27 @@ int main(int argc, char ** argv) {
         return 1;
     }
 
-    float * logits;
-    int n_logits;
+    float * data_ptr;
+    int data_size;
     const char * type;
+    std::vector<float> embd_out;
 
     if (embedding_mode) {
-        logits = llama_get_embeddings(ctx);
-        n_logits = llama_model_n_embd(model) * batch.n_tokens;
+        const int n_embd = llama_model_n_embd(model);
+        const int n_embd_count = pooling_enabled ? 1 : batch.n_tokens;
+        const int n_embeddings = n_embd * n_embd_count;
+        float * embeddings;
         type = "-embeddings";
 
-        const int n_embd = llama_model_n_embd(model);
-        const int n_embd_count = batch.n_tokens;
+        if (llama_pooling_type(ctx) != LLAMA_POOLING_TYPE_NONE) {
+            embeddings = llama_get_embeddings_seq(ctx, 0);
+            embd_out.resize(n_embeddings);
+            printf("Normalizing embeddings using norm: %d\n", embd_norm);
+            common_embd_normalize(embeddings, embd_out.data(), n_embeddings, embd_norm);
+            embeddings = embd_out.data();
+        } else {
+            embeddings = llama_get_embeddings(ctx);
+        }
 
         printf("Embedding dimension: %d\n", n_embd);
         printf("\n");
@@ -164,7 +186,7 @@ int main(int argc, char ** argv) {
 
             // Print first 3 values
             for (int i = 0; i < 3 && i < n_embd; i++) {
-                printf("%9.6f ", logits[j * n_embd + i]);
+                printf("%9.6f ", embeddings[j * n_embd + i]);
             }
 
             printf(" ... ");
@@ -172,7 +194,7 @@ int main(int argc, char ** argv) {
             // Print last 3 values
             for (int i = n_embd - 3; i < n_embd; i++) {
                 if (i >= 0) {
-                    printf("%9.6f ", logits[j * n_embd + i]);
+                    printf("%9.6f ", embeddings[j * n_embd + i]);
                 }
             }
 
@@ -180,27 +202,33 @@ int main(int argc, char ** argv) {
         }
         printf("\n");
 
-        printf("Embeddings size: %d\n", n_logits);
+        printf("Embeddings size: %d\n", n_embeddings);
+
+        data_ptr = embeddings;
+        data_size = n_embeddings;
     } else {
-        logits = llama_get_logits_ith(ctx, batch.n_tokens - 1);
-        n_logits = llama_vocab_n_tokens(vocab);
+        float * logits = llama_get_logits_ith(ctx, batch.n_tokens - 1);
+        const int n_logits = llama_vocab_n_tokens(vocab);
         type = "";
         printf("Vocab size: %d\n", n_logits);
+
+        data_ptr = logits;
+        data_size = n_logits;
     }
 
     std::filesystem::create_directory("data");
 
-    // Save logits to binary file
+    // Save data to binary file
     char bin_filename[512];
     snprintf(bin_filename, sizeof(bin_filename), "data/llamacpp-%s%s.bin", model_name, type);
-    printf("Saving logits to %s\n", bin_filename);
+    printf("Saving data to %s\n", bin_filename);
 
     FILE * f = fopen(bin_filename, "wb");
     if (f == NULL) {
         fprintf(stderr, "%s: error: failed to open binary output file\n", __func__);
         return 1;
     }
-    fwrite(logits, sizeof(float), n_logits, f);
+    fwrite(data_ptr, sizeof(float), data_size, f);
     fclose(f);
 
     // Also save as text for debugging
@@ -211,27 +239,27 @@ int main(int argc, char ** argv) {
         fprintf(stderr, "%s: error: failed to open text output file\n", __func__);
         return 1;
     }
-    for (int i = 0; i < n_logits; i++) {
-        fprintf(f, "%d: %.6f\n", i, logits[i]);
+    for (int i = 0; i < data_size; i++) {
+        fprintf(f, "%d: %.6f\n", i, data_ptr[i]);
     }
     fclose(f);
 
     if (!embedding_mode) {
         printf("First 10 logits: ");
-        for (int i = 0; i < 10 && i < n_logits; i++) {
-            printf("%.6f ", logits[i]);
+        for (int i = 0; i < 10 && i < data_size; i++) {
+            printf("%.6f ", data_ptr[i]);
         }
         printf("\n");
 
         printf("Last 10 logits: ");
-        for (int i = n_logits - 10; i < n_logits; i++) {
-            if (i >= 0) printf("%.6f ", logits[i]);
+        for (int i = data_size - 10; i < data_size; i++) {
+            if (i >= 0) printf("%.6f ", data_ptr[i]);
         }
         printf("\n\n");
     }
 
-    printf("Logits saved to %s\n", bin_filename);
-    printf("Logits saved to %s\n", txt_filename);
+    printf("Data saved to %s\n", bin_filename);
+    printf("Data saved to %s\n", txt_filename);
 
     llama_free(ctx);
     llama_model_free(model);