llama : support requantizing models instead of only allowing quantization from 16/32bit (#1691)

* Add support for quantizing already quantized models

* Threaded dequantizing and f16 to f32 conversion

* Clean up thread blocks with spares calculation a bit

* Use std::runtime_error exceptions.

1 files changed, 38 insertions, 19 deletions

diff --git a/examples/quantize/quantize.cpp b/examples/quantize/quantize.cpp
index 947b402..c6bf1b7 100644
--- a/examples/quantize/quantize.cpp
+++ b/examples/quantize/quantize.cpp
@@ -3,6 +3,7 @@
 #include "llama.h"
 
 #include <cstdio>
+#include <cstring>
 #include <map>
 #include <string>
 
@@ -53,27 +54,49 @@ bool try_parse_ftype(const std::string & ftype_str, llama_ftype & ftype, std::st
 // usage:
 //  ./quantize models/llama/ggml-model.bin [models/llama/ggml-model-quant.bin] type [nthreads]
 //
+void usage(const char * executable) {
+    fprintf(stderr, "usage: %s [--help] [--allow-requantize] [--leave-output-tensor] model-f32.bin [model-quant.bin] type [nthreads]\n", executable);
+    fprintf(stderr, "  --allow-requantize: Allows requantizing tensors that have already been quantized. Warning: This can severely reduce quality compared to quantizing from 16bit or 32bit\n");
+    fprintf(stderr, "  --leave-output-tensor: Will leave output.weight un(re)quantized. Increases model size but may also increase quality, especially when requantizing\n");
+    fprintf(stderr, "Allowed quantization types:\n");
+    for (auto it = LLAMA_FTYPE_MAP.begin(); it != LLAMA_FTYPE_MAP.end(); it++) {
+        fprintf(stderr, "  type = \"%s\" or %d\n", it->first.c_str(), it->second);
+    }
+    exit(1);
+}
+
 int main(int argc, char ** argv) {
     if (argc < 3) {
-        fprintf(stderr, "usage: %s model-f32.bin [model-quant.bin] type [nthreads]\n", argv[0]);
-        for (auto it = LLAMA_FTYPE_MAP.begin(); it != LLAMA_FTYPE_MAP.end(); it++) {
-            fprintf(stderr, "  type = \"%s\" or %d\n", it->first.c_str(), it->second);
+        usage(argv[0]);
+    }
+
+    llama_model_quantize_params params = llama_model_quantize_default_params();
+
+    int arg_idx = 1;
+
+    for (; arg_idx < argc && strncmp(argv[arg_idx], "--", 2) == 0; arg_idx++) {
+        if (strcmp(argv[arg_idx], "--leave-output-tensor") == 0) {
+            params.quantize_output_tensor = false;
+        } else if (strcmp(argv[arg_idx], "--allow-requantize") == 0) {
+            params.allow_requantize = true;
+        } else {
+            usage(argv[0]);
         }
-        return 1;
+    }
+
+    if (argc - arg_idx < 3) {
+        usage(argv[0]);
     }
 
     llama_init_backend();
 
     // parse command line arguments
-    const std::string fname_inp = argv[1];
+    const std::string fname_inp = argv[arg_idx];
+    arg_idx++;
     std::string fname_out;
-    int nthread;
-    llama_ftype ftype;
 
-    int arg_idx = 2;
     std::string ftype_str;
-    if (try_parse_ftype(argv[arg_idx], ftype, ftype_str)) {
-        // argv[2] is the ftype
+    if (try_parse_ftype(argv[arg_idx], params.ftype, ftype_str)) {
         std::string fpath;
         const size_t pos = fname_inp.find_last_of('/');
         if (pos != std::string::npos) {
@@ -84,7 +107,6 @@ int main(int argc, char ** argv) {
         arg_idx++;
     }
     else {
-        // argv[2] is the output path
         fname_out = argv[arg_idx];
         arg_idx++;
 
@@ -92,8 +114,7 @@ int main(int argc, char ** argv) {
             fprintf(stderr, "%s: missing ftype\n", __func__);
             return 1;
         }
-        // argv[3] is the ftype
-        if (!try_parse_ftype(argv[arg_idx], ftype, ftype_str)) {
+        if (!try_parse_ftype(argv[arg_idx], params.ftype, ftype_str)) {
             fprintf(stderr, "%s: invalid ftype '%s'\n", __func__, argv[3]);
             return 1;
         }
@@ -103,21 +124,19 @@ int main(int argc, char ** argv) {
     // parse nthreads
     if (argc > arg_idx) {
         try {
-            nthread = std::stoi(argv[arg_idx]);
+            params.nthread = std::stoi(argv[arg_idx]);
         }
         catch (const std::exception & e) {
             fprintf(stderr, "%s: invalid nthread '%s' (%s)\n", __func__, argv[arg_idx], e.what());
             return 1;
         }
-    } else {
-        nthread = 0;
     }
 
     fprintf(stderr, "%s: build = %d (%s)\n", __func__, BUILD_NUMBER, BUILD_COMMIT);
 
     fprintf(stderr, "%s: quantizing '%s' to '%s' as %s", __func__, fname_inp.c_str(), fname_out.c_str(), ftype_str.c_str());
-    if (nthread > 0) {
-        fprintf(stderr, " using %d threads", nthread);
+    if (params.nthread > 0) {
+        fprintf(stderr, " using %d threads", params.nthread);
     }
     fprintf(stderr, "\n");
 
@@ -129,7 +148,7 @@ int main(int argc, char ** argv) {
     {
         const int64_t t_start_us = llama_time_us();
 
-        if (llama_model_quantize(fname_inp.c_str(), fname_out.c_str(), ftype, nthread)) {
+        if (llama_model_quantize(fname_inp.c_str(), fname_out.c_str(), &params)) {
             fprintf(stderr, "%s: failed to quantize model from '%s'\n", __func__, fname_inp.c_str());
             return 1;
         }