ggml-quants : use ceiling division when quantizing q1_3

Author: compilade

convert-hf-to-gguf.py

@@ -334,7 +334,7 @@ def write_tensors(self):
                 shape = gguf.quant_shape_from_byte_shape(data.shape, data_qtype) if data.dtype == np.uint8 else data.shape
 
                 # reverse shape to make it similar to the internal ggml dimension order
-                shape_str = f"{{{', '.join(str(n) for n in reversed(shape))}}}"
+                shape_str = f"{{{', '.join(str(n) for n in reversed(shape)) or '1'}}}"
 
                 # n_dims is implicit in the shape
                 logger.info(f"{f'%-{max_name_len}s' % f'{new_name},'} {old_dtype} --> {data_qtype.name}, shape = {shape_str}")

ggml-quants.c

@@ -3389,8 +3389,8 @@ void quantize_row_q1_3_reference(const float * restrict x, block_q1_3 * restrict
             int xi = nearest_int(x[j]);
             uint8_t xt = xi < 0 ? 0 : xi == 0 ? 1 : 2;
             q[j] += xt * pow3[4];
-            q[j] = ((uint16_t)q[j] * 256) / pow3[5];
-            q[j] += (uint8_t)(q[j] != 0);
+            // ceiling division
+            q[j] = ((uint16_t)q[j] * 256 + (pow3[5] - 1)) / pow3[5];
             y[i].q[j] = q[j];
         }
         x += sizeof(y->q);
@@ -3403,8 +3403,8 @@ void quantize_row_q1_3_reference(const float * restrict x, block_q1_3 * restrict
                 qb += xt * pow3[m];
             }
             x += 4;
-            qb = ((uint16_t)qb * 256) / pow3[5];
-            qb += (uint8_t)(qb != 0);
+            // ceiling division
+            qb = ((uint16_t)qb * 256 + (pow3[5] - 1)) / pow3[5];
             y[i].qs[j] = qb;
         }
     }

gguf-py/gguf/quants.py

@@ -149,8 +149,7 @@ def __quantize_q1_3_rows(n: np.ndarray) -> np.ndarray:
     q4 = np.sum(q4 * pow3.reshape((1, 4)), axis=1, keepdims=True)
     q48 = q48 + (q12 * 81)
     q = np.concatenate([q48, q4], axis=1)
-    q = ((q.astype(np.uint16) * 256) // 243).astype(np.uint8)
-    q = np.where(q != 0, q + 1, 0)
+    q = (((q.astype(np.uint16) * 256) + (243 - 1)) // 243).astype(np.uint8)
 
     return q.reshape(__quantize_q1_3_shape_change(shape))
 

tests/test-quantize-fns.cpp

@@ -15,11 +15,13 @@
 
 constexpr float MAX_QUANTIZATION_REFERENCE_ERROR = 0.0001f;
 constexpr float MAX_QUANTIZATION_TOTAL_ERROR = 0.002f;
+constexpr float MAX_QUANTIZATION_TOTAL_ERROR_BITNET = 0.015625f;
 constexpr float MAX_QUANTIZATION_TOTAL_ERROR_2BITS = 0.0075f;
 constexpr float MAX_QUANTIZATION_TOTAL_ERROR_3BITS = 0.0040f;
 constexpr float MAX_QUANTIZATION_TOTAL_ERROR_3BITS_XXS = 0.0050f;
 constexpr float MAX_DOT_PRODUCT_ERROR = 0.02f;
 constexpr float MAX_DOT_PRODUCT_ERROR_LOWBIT = 0.04f;
+constexpr float MAX_DOT_PRODUCT_ERROR_BITNET = 0.5f;
 
 static const char* RESULT_STR[] = {"ok", "FAILED"};
 
@@ -144,6 +146,8 @@ int main(int argc, char * argv[]) {
         if (qfns.from_float && qfns.to_float) {
             const float total_error = total_quantization_error(qfns, test_size, test_data.data());
             const float max_quantization_error =
+                type == GGML_TYPE_Q1_3    ? MAX_QUANTIZATION_TOTAL_ERROR_BITNET :
+                type == GGML_TYPE_Q2_2    ? MAX_QUANTIZATION_TOTAL_ERROR_BITNET :
                 type == GGML_TYPE_Q2_K    ? MAX_QUANTIZATION_TOTAL_ERROR_2BITS :
                 type == GGML_TYPE_IQ2_S   ? MAX_QUANTIZATION_TOTAL_ERROR_2BITS :
                 type == GGML_TYPE_Q3_K    ? MAX_QUANTIZATION_TOTAL_ERROR_3BITS :
@@ -166,6 +170,8 @@ int main(int argc, char * argv[]) {
             const float max_allowed_error = type == GGML_TYPE_Q2_K || type == GGML_TYPE_IQ2_XS || type == GGML_TYPE_IQ2_XXS ||
                                             type == GGML_TYPE_IQ3_XXS || type == GGML_TYPE_IQ3_S || type == GGML_TYPE_IQ2_S
                                           ? MAX_DOT_PRODUCT_ERROR_LOWBIT
+                                          : type == GGML_TYPE_Q2_2 || type == GGML_TYPE_Q1_3
+                                          ? MAX_DOT_PRODUCT_ERROR_BITNET
                                           : MAX_DOT_PRODUCT_ERROR;
             failed = !(vec_dot_error < max_allowed_error);
             num_failed += failed;