deduplicate code for get_group_qparams_symmetric

Summary:
This just removes the implementation, we can have follow up PRs to remove the call all together
after we have replaced all implementation with the new blockwise quant code

Test Plan:
CI

Reviewers:

Subscribers:

Tasks:

Tags:

test/quantization/test_quant_primitives.py

@@ -67,9 +67,11 @@ def test_choose_qparams_group_sym(self):
         mapping_type = MappingType.SYMMETRIC
         dtype = torch.int8
         block_size = (1, 2)
-        scale, zero_point = choose_qparams_affine(input, mapping_type, block_size, dtype, eps=torch.finfo(torch.float32).eps)
+        eps = torch.finfo(torch.float32).eps
+        precision = torch.float32
+        scale, zero_point = choose_qparams_affine(input, mapping_type, block_size, dtype, eps=eps, scale_dtype=precision, zero_point_dtype=precision)
 
-        scale_ref, zp_ref = get_group_qparams_symmetric(input, n_bit=8, groupsize=2)
+        scale_ref, zp_ref = get_group_qparams_symmetric(input, n_bit=8, groupsize=2, precision=precision)
 
         self.assertTrue(torch.equal(scale, scale_ref))
         self.assertTrue(torch.equal(zero_point, zp_ref))

torchao/quantization/quant_primitives.py

@@ -40,6 +40,9 @@
     "groupwise_affine_dequantize_tensor_from_qparams",
     "groupwise_affine_quantize_tensor",
     "groupwise_affine_dequantize_tensor",
+    "choose_qparams_affine",
+    "quantize_affine",
+    "dequantize_affine",
     # TODO: need to clean up above functions
 ] + (_AFTER_TORCH_2_3_ONLY if TORCH_VERSION_AFTER_2_3 else [])
 
@@ -728,26 +731,18 @@ def get_group_qparams_symmetric(w, n_bit=4, groupsize=128, precision=torch.float
     assert groupsize > 1
     assert w.shape[-1] % groupsize == 0
     assert w.dim() == 2
+    assert n_bit <= 8, f"unsupported n_bit: {n_bit}"
 
-    to_quant = w.reshape(-1, groupsize)
-    assert torch.isnan(to_quant).sum() == 0
-
-    max_val = to_quant.amax(dim=1, keepdim=True)
-    min_val = to_quant.amin(dim=1, keepdim=True)
-    min_val_neg = torch.min(min_val, torch.zeros_like(min_val))
-    max_val_pos = torch.max(max_val, torch.zeros_like(max_val))
-
-    max_val_abs = torch.max(-min_val_neg, max_val_pos)
-    max_int = 2 ** (n_bit - 1) - 1
-    min_int = -(2 ** (n_bit - 1))
-
-    scales = max_val_abs / (float(max_int - min_int) / 2)
-    scales = torch.max(scales, torch.full_like(scales, torch.finfo(torch.float32).eps))
-    # TODO: make sure abs(scales) is not too small?
-    zeros = torch.full_like(scales, 0)
-    return scales.to(precision).reshape(w.shape[0], -1), zeros.to(precision).reshape(
-        w.shape[0], -1
-    )
+    block_size = (1, groupsize)
+    mapping_type = MappingType.SYMMETRIC
+    eps = torch.finfo(torch.float32).eps
+    ranges = {}
+    ranges[1] = (-1, 0)
+    # generating ranges for bit 2 to 8
+    for i in range(2, 9):
+        ranges[i] = (-(2 ** (i - 1)), 2 ** (i - 1) - 1)
+    quant_min, quant_max = ranges[n_bit]
+    return choose_qparams_affine(w, mapping_type, block_size, target_dtype=torch.int8, quant_min=quant_min, quant_max=quant_max, eps=eps, scale_dtype=precision, zero_point_dtype=precision)
 
 
 if TORCH_VERSION_AFTER_2_3: