finetune : fix ggml_allocr lifetimes (tmp workaround) (#5033)

* Fix issue with alloc causing max_compute_size to be calculated

* remove ggml_allocr_free as suggested in issue #4791

examples/train-text-from-scratch/train-text-from-scratch.cpp

@@ -263,7 +263,6 @@ static void init_model(struct my_llama_model * model) {
     model->data.resize(size + tensor_alignment);
     alloc = ggml_allocr_new(model->data.data(), model->data.size(), tensor_alignment);
     alloc_model(alloc, model);
-    ggml_allocr_free(alloc);
 }
 
 static void randomize_model(struct my_llama_model * model, int seed, float mean, float std, float min, float max) {
@@ -1102,7 +1101,6 @@ int main(int argc, char ** argv) {
     alloc = ggml_allocr_new(mem_input_data.data(), mem_input_data.size(), tensor_alignment);
     ggml_allocr_alloc(alloc, tokens_input);
     ggml_allocr_alloc(alloc, target_probs);
-    ggml_allocr_free(alloc);
 
     // context for compute tensors without their data
     const size_t estimated_compute_size_wo_data = (
@@ -1149,7 +1147,6 @@ int main(int argc, char ** argv) {
             best_compute_size = max_compute_size;
             best_order = gf->order;
         }
-        ggml_allocr_free(alloc);
         ggml_free(ctx_compute);
     }
     size_t max_compute_size = best_compute_size;
@@ -1177,7 +1174,6 @@ int main(int argc, char ** argv) {
         params.common.use_flash,
         params.common.use_checkpointing
     );
-    ggml_allocr_free(alloc);
 
     std::vector<llama_token> train_tokens;
     std::vector<size_t> train_samples_begin;