llama : add api for getting/setting the complete state: rng, logits, embedding and kv_cache (#1105)

* reserve correct size for logits

* add functions to get and set the whole llama state:

including rng, logits, embedding and kv_cache

* remove unused variables

* remove trailing whitespace

* fix comment

2 files changed, 133 insertions, 1 deletions

diff --git a/llama.cpp b/llama.cpp
index 0345b61..00cce6e 100644
--- a/llama.cpp
+++ b/llama.cpp
@@ -27,6 +27,7 @@
 #include <thread>
 #include <atomic>
 #include <mutex>
+#include <sstream>
 
 #define LLAMA_USE_SCRATCH
 #define LLAMA_MAX_SCRATCH_BUFFERS 16
@@ -1787,7 +1788,7 @@ struct llama_context * llama_init_from_file(
         if (params.logits_all) {
             ctx->logits.reserve(hparams.n_ctx*hparams.n_vocab);
         } else {
-            ctx->logits.reserve(hparams.n_ctx);
+            ctx->logits.reserve(hparams.n_vocab);
         }
 
         if (params.embedding){
@@ -2252,3 +2253,122 @@ const char * llama_print_system_info(void) {
 std::vector<std::pair<std::string, struct ggml_tensor *>>& llama_internal_get_tensor_map(struct llama_context * ctx) {
     return ctx->model.tensors_by_name;
 }
+
+// Returns the size of the state
+size_t llama_get_state_size(struct llama_context * ctx) {
+    const size_t s_bool = sizeof(int32_t);
+    // we don't know size of rng until we actually serialize it. so reserve more than enough memory for its serialized state.
+    // for reference, std::mt19937(1337) serializes to 6701 bytes.
+    const size_t s_rng_size = sizeof(size_t);
+    const size_t s_rng = 64*1024;
+    const size_t s_logits_capacity = sizeof(size_t);
+    const size_t s_logits_size = sizeof(size_t);
+    const size_t s_logits = ctx->logits.capacity() * sizeof(float);
+    const size_t s_embedding_size = sizeof(size_t);
+    const size_t s_embedding = ctx->embedding.size() * sizeof(float);
+    const size_t s_kv_size = sizeof(size_t);
+    const size_t s_kv_ntok = sizeof(int);
+    const size_t s_kv = llama_get_kv_cache_size(ctx);
+    const size_t s_total = (
+        + s_rng_size
+        + s_rng
+        + s_logits_capacity
+        + s_logits_size
+        + s_logits
+        + s_embedding_size
+        + s_embedding
+        + s_kv_size
+        + s_kv_ntok
+        + s_kv
+    );
+    return s_total;
+}
+
+// Copies the state to the specified destination address
+size_t llama_copy_state_data(struct llama_context * ctx, uint8_t * dest) {
+    std::stringstream rng_ss;
+    rng_ss << ctx->rng;
+    const size_t rng_size = rng_ss.str().size();
+    char rng_buf[64*1024];
+    memset(&rng_buf[0], 0, 64*1024);
+    memcpy(&rng_buf[0], rng_ss.str().data(), rng_ss.str().size());
+    const size_t logits_capacity = ctx->logits.capacity();
+    const size_t logits_size = ctx->logits.size();
+    const size_t embedding_size = ctx->embedding.size();
+    const size_t kv_size = llama_get_kv_cache_size(ctx);
+    const int kv_ntok = llama_get_kv_cache_token_count(ctx);
+
+    uint8_t * out = dest;
+    memcpy(out, &rng_size, sizeof(size_t)); out += sizeof(size_t);
+    memcpy(out, &rng_buf[0], 64*1024); out += 64*1024;
+    memcpy(out, &logits_capacity, sizeof(size_t)); out += sizeof(size_t);
+    memcpy(out, &logits_size, sizeof(size_t)); out += sizeof(size_t);
+    if (logits_size) {
+        memcpy(out, ctx->logits.data(), logits_size * sizeof(float));
+    }
+    out += logits_capacity * sizeof(float);
+    memcpy(out, &embedding_size, sizeof(size_t)); out += sizeof(size_t);
+    if (embedding_size) {
+        memcpy(out, ctx->embedding.data(), embedding_size * sizeof(float)); out += embedding_size * sizeof(float);
+    }
+    memcpy(out, &kv_size, sizeof(size_t)); out += sizeof(size_t);
+    memcpy(out, &kv_ntok, sizeof(int)); out += sizeof(int);
+    if (kv_size) {
+        memcpy(out, llama_get_kv_cache(ctx), kv_size); out += kv_size;
+    }
+    const size_t written = out - dest;
+    const size_t expected = llama_get_state_size(ctx);
+    LLAMA_ASSERT(written == expected);
+    return written;
+}
+
+// Sets the state reading from the specified source address
+size_t llama_set_state_data(struct llama_context * ctx, const uint8_t * src) {
+    size_t rng_size;
+    char rng_buf[64*1024];
+    std::stringstream rng_ss;
+
+    const uint8_t * in = src;
+    memcpy(&rng_size, in, sizeof(size_t)); in += sizeof(size_t);
+    memcpy(&rng_buf[0], in, 64*1024); in += 64*1024;
+    rng_ss.str(std::string(&rng_buf[0], rng_size));
+    rng_ss >> ctx->rng;
+    LLAMA_ASSERT(rng_ss.fail() == false);
+
+    size_t logits_capacity;
+    size_t logits_size;
+    size_t embedding_size;
+    size_t kv_size;
+    int kv_ntok;
+
+    memcpy(&logits_capacity, in, sizeof(size_t)); in += sizeof(size_t);
+    memcpy(&logits_size, in, sizeof(size_t)); in += sizeof(size_t);
+    LLAMA_ASSERT(ctx->logits.capacity() == logits_capacity);
+    if (logits_size) {
+        ctx->logits.resize(logits_size);
+        memcpy(ctx->logits.data(), in, logits_size * sizeof(float));
+    }
+    in += logits_capacity * sizeof(float);
+    memcpy(&embedding_size, in, sizeof(size_t)); in += sizeof(size_t);
+    LLAMA_ASSERT(ctx->embedding.capacity() == embedding_size);
+    if (embedding_size) {
+        memcpy(ctx->embedding.data(), in, embedding_size * sizeof(float));
+        in += embedding_size * sizeof(float);
+    }
+    memcpy(&kv_size, in, sizeof(size_t)); in += sizeof(size_t);
+    memcpy(&kv_ntok, in, sizeof(int)); in += sizeof(int);
+    if (kv_size) {
+        LLAMA_ASSERT(ctx->model.kv_self.buf.size == kv_size);
+        void * k_data = ctx->model.kv_self.k->data; // remember data pointers
+        void * v_data = ctx->model.kv_self.v->data; // because their value is stored in buf and overwritten by memcpy
+        memcpy(ctx->model.kv_self.buf.addr, in, kv_size);
+        ctx->model.kv_self.k->data = k_data; // restore correct data pointers
+        ctx->model.kv_self.v->data = v_data;
+        in += kv_size;
+    }
+    ctx->model.kv_self.n = kv_ntok;
+    const size_t nread = in - src;
+    const size_t expected = llama_get_state_size(ctx);
+    LLAMA_ASSERT(nread == expected);
+    return nread;
+}
diff --git a/llama.h b/llama.h
index e95ff73..f68a0cb 100644
--- a/llama.h
+++ b/llama.h
@@ -129,6 +129,18 @@ extern "C" {
                           size_t   n_size,
                              int   n_token_count);
 
+    // Returns the size in bytes of the state (rng, logits, embedding and kv_cache)
+    LLAMA_API size_t llama_get_state_size(struct llama_context * ctx);
+
+    // Copies the state to the specified destination address.
+    // Destination needs to have allocated enough memory.
+    // Returns the number of bytes copied
+    LLAMA_API size_t llama_copy_state_data(struct llama_context * ctx, uint8_t * dest);
+
+    // Set the state reading from the specified address
+    // Returns the number of bytes read
+    LLAMA_API size_t llama_set_state_data(struct llama_context * ctx, const uint8_t * src);
+
     // Run the llama inference to obtain the logits and probabilities for the next token.
     // tokens + n_tokens is the provided batch of new tokens to process
     // n_past is the number of tokens to use from previous eval calls