diff --git a/training/train_double_buffer.m b/training/train_double_buffer.m
index a74eabe..66cc359 100644
--- a/training/train_double_buffer.m
+++ b/training/train_double_buffer.m
@@ -282,15 +282,30 @@ int main(int argc, char *argv[]) {
             printf("ANE FLOPs/step: %.0fM (fwd+bwd_dx+sdpa_bwd) | CPU: dW+cls (cblas)\n\n", ane_f/1e6);
         }
 
-        // mmap token data
+        // mmap token data (or generate synthetic if not available)
+        uint16_t *token_data = NULL;
+        size_t n_tokens = 0;
+        size_t data_len = 0;
+        bool synthetic_data = false;
         int data_fd = open(DATA_PATH, O_RDONLY);
-        if (data_fd < 0) { printf("Cannot open %s\n", DATA_PATH); return 1; }
-        struct stat st; fstat(data_fd, &st);
-        size_t data_len = st.st_size;
-        uint16_t *token_data = (uint16_t*)mmap(NULL, data_len, PROT_READ, MAP_PRIVATE, data_fd, 0);
-        if (token_data == MAP_FAILED) { printf("mmap failed\n"); return 1; }
-        size_t n_tokens = data_len / 2;
-        printf("Token data: %zu tokens (%.1f MB)\n", n_tokens, data_len/1e6);
+        if (data_fd >= 0) {
+            struct stat st; fstat(data_fd, &st);
+            data_len = st.st_size;
+            token_data = (uint16_t*)mmap(NULL, data_len, PROT_READ, MAP_PRIVATE, data_fd, 0);
+            if (token_data == MAP_FAILED) { printf("mmap failed\n"); return 1; }
+            n_tokens = data_len / 2;
+            printf("Token data: %zu tokens (%.1f MB)\n", n_tokens, data_len/1e6);
+        } else {
+            // Synthetic data for double-buffer benchmark
+            synthetic_data = true;
+            n_tokens = 100000;
+            data_len = n_tokens * 2;
+            token_data = (uint16_t*)malloc(data_len);
+            srand48(123);
+            for (size_t i = 0; i < n_tokens; i++)
+                token_data[i] = (uint16_t)(drand48() * (VOCAB - 1));
+            printf("[DB] Using synthetic data: %zu tokens (benchmark mode)\n", n_tokens);
+        }
 
         // Gradient buffers shared across layers (reused each step)
         float *dy = (float*)malloc(SEQ*DIM*4);            // gradient flowing backward
@@ -748,8 +763,8 @@ int main(int argc, char *argv[]) {
             layer_acts_free(&acts[L]);
             layer_grads_free(&grads[L]);
         }
-        munmap(token_data, data_len);
-        close(data_fd);
+        if (synthetic_data) { free(token_data); }
+        else { munmap(token_data, data_len); close(data_fd); }
         free(rms_final); free(embed); free(grms_final); free(gembed);
         adam_free(&arms_final); adam_free(&aembed);
         free(dy); free(dffn); free(dh1); free(dh3); free(dx_ffn); free(dx2);