CLI default KV type: uniform_4b → turbo_kv_4b

Variant F validation across two models confirms turbo_kv_4b beats
uniform_4b at the same 4-bit budget on both:

  SmolLM2 135M  (FP32 18.62):
    uniform_4b   20.33  (+9.2%)
    turbo_kv_4b  19.70  (+5.8%)  ✅ -3.1% PPL improvement

  Llama 3.2 3B  (FP32 13.56):
    uniform_4b   14.41  (+6.3%)
    turbo_kv_4b  14.28  (+5.3%)  ✅ -0.9% PPL improvement

Smaller model = larger relative improvement, consistent with the
finer codebook (16 levels vs 15) capturing more of the per-block
distribution detail.

Switching the CLI default so users get the better quantization
without having to know the type name. uniform_4b remains available
via -k uniform_4b.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: unamedkr

tools/quant.c

@@ -12,7 +12,7 @@
  *   -P <top_p>       Top-p nucleus sampling (default: 0.9)
  *   -k <kv_type>     KV cache type: fp32, uniform_4b, uniform_2b,
  *                     polar_3b, polar_4b, turbo_3b, turbo_4b,
- *                     turbo_kv_1b, turbo_kv_3b, turbo_kv_4b (default: uniform_4b)
+ *                     turbo_kv_1b, turbo_kv_3b, turbo_kv_4b (default: turbo_kv_4b)
  *   -v <vq>          Value cache quantization: q4 (4-bit), q2 (2-bit),
  *                     or fp16 (default: fp16 when -k is set, fp32 otherwise)
  *   -j <threads>     Number of threads for matmul (default: 4)
@@ -71,7 +71,7 @@ static void print_token(const char* text, void* user_data) {
 
 /* Parse KV type from string */
 static tq_type parse_kv_type(const char* s) {
-    if (!s) return TQ_TYPE_UNIFORM_4B;
+    if (!s) return TQ_TYPE_TURBO_KV_4B;
     if (strcmp(s, "fp32") == 0)       return TQ_TYPE_COUNT; /* sentinel for FP32 */
     if (strcmp(s, "uniform_4b") == 0) return TQ_TYPE_UNIFORM_4B;
     if (strcmp(s, "uniform_2b") == 0) return TQ_TYPE_UNIFORM_2B;
@@ -85,8 +85,8 @@ static tq_type parse_kv_type(const char* s) {
     if (strcmp(s, "qjl_1b") == 0)     return TQ_TYPE_QJL_1B;
     if (strcmp(s, "mixed_4b8") == 0)  return TQ_TYPE_MIXED_4B8;
     if (strcmp(s, "uniform_3b") == 0) return TQ_TYPE_UNIFORM_3B;
-    fprintf(stderr, "Unknown KV type: %s (using uniform_4b)\n", s);
-    return TQ_TYPE_UNIFORM_4B;
+    fprintf(stderr, "Unknown KV type: %s (using turbo_kv_4b)\n", s);
+    return TQ_TYPE_TURBO_KV_4B;
 }
 
 #define QUANT_VERSION "0.2.0"
@@ -145,7 +145,7 @@ int main(int argc, char** argv) {
     int max_tokens = 256;
     float temperature = 0.7f;
     float top_p = 0.9f;
-    tq_type kv_type = TQ_TYPE_UNIFORM_4B;
+    tq_type kv_type = TQ_TYPE_TURBO_KV_4B;
     int n_threads = 4;
     int quant_mode = 0;   /* 0 = none (default), 2 = Q2, 4 = Q4, 8 = Q8 */
     int value_quant_bits = 0; /* 0 = FP16/FP32 (default), 4 = Q4, 2 = Q2 */