Fix batched qmv bug (#1758)

Author: barronalex

mlx/backend/metal/kernels/quantized.h

@@ -1323,13 +1323,14 @@ template <typename T, int group_size, int bits, int D, bool batched>
     uint quad_gid [[quadgroup_index_in_threadgroup]],
     uint quad_lid [[thread_index_in_quadgroup]]) {
   if (batched) {
+    int M = x_shape[x_batch_ndims];
     adjust_matrix_offsets<T>(
         x,
         w,
         scales,
         biases,
         y,
-        out_vec_size,
+        out_vec_size * M,
         x_batch_ndims,
         x_shape,
         x_strides,
@@ -1374,13 +1375,14 @@ template <typename T, int group_size, int bits, bool batched>
     uint simd_gid [[simdgroup_index_in_threadgroup]],
     uint simd_lid [[thread_index_in_simdgroup]]) {
   if (batched) {
+    int M = x_shape[x_batch_ndims];
     adjust_matrix_offsets<T>(
         x,
         w,
         scales,
         biases,
         y,
-        out_vec_size,
+        out_vec_size * M,
         x_batch_ndims,
         x_shape,
         x_strides,
@@ -1425,13 +1427,14 @@ template <typename T, const int group_size, const int bits, bool batched>
     uint simd_gid [[simdgroup_index_in_threadgroup]],
     uint simd_lid [[thread_index_in_simdgroup]]) {
   if (batched) {
+    int M = x_shape[x_batch_ndims];
     adjust_matrix_offsets<T>(
         x,
         w,
         scales,
         biases,
         y,
-        out_vec_size,
+        out_vec_size * M,
         x_batch_ndims,
         x_shape,
         x_strides,
@@ -1476,13 +1479,14 @@ template <typename T, const int group_size, const int bits, bool batched>
     uint simd_gid [[simdgroup_index_in_threadgroup]],
     uint simd_lid [[thread_index_in_simdgroup]]) {
   if (batched) {
+    int M = x_shape[x_batch_ndims];
     adjust_matrix_offsets<T>(
         x,
         w,
         scales,
         biases,
         y,
-        out_vec_size,
+        out_vec_size * M,
         x_batch_ndims,
         x_shape,
         x_strides,
@@ -1527,13 +1531,14 @@ template <typename T, const int group_size, const int bits, int split_k = 32>
     uint3 tid [[threadgroup_position_in_grid]],
     uint simd_gid [[simdgroup_index_in_threadgroup]],
     uint simd_lid [[thread_index_in_simdgroup]]) {
+  int M = x_shape[x_batch_ndims];
   adjust_matrix_offsets<T>(
       x,
       w,
       scales,
       biases,
       y,
-      out_vec_size,
+      out_vec_size * M,
       x_batch_ndims,
       x_shape,
       x_strides,
@@ -1706,6 +1711,7 @@ template <typename T, int group_size, int bits>
     uint3 tid [[threadgroup_position_in_grid]],
     uint simd_gid [[simdgroup_index_in_threadgroup]],
     uint simd_lid [[thread_index_in_simdgroup]]) {
+  int M = x_shape[x_batch_ndims];
   adjust_matrix_offsets<T>(
       x,
       w,
@@ -1714,7 +1720,7 @@ template <typename T, int group_size, int bits>
       lhs_indices,
       rhs_indices,
       y,
-      out_vec_size,
+      out_vec_size * M,
       batch_ndims,
       batch_shape,
       lhs_strides,
@@ -1767,6 +1773,7 @@ template <typename T, int group_size, int bits>
     uint3 tid [[threadgroup_position_in_grid]],
     uint simd_gid [[simdgroup_index_in_threadgroup]],
     uint simd_lid [[thread_index_in_simdgroup]]) {
+  int M = x_shape[x_batch_ndims];
   adjust_matrix_offsets<T>(
       x,
       w,
@@ -1775,7 +1782,7 @@ template <typename T, int group_size, int bits>
       lhs_indices,
       rhs_indices,
       y,
-      out_vec_size,
+      out_vec_size * M,
       batch_ndims,
       batch_shape,
       lhs_strides,
@@ -1828,6 +1835,7 @@ template <typename T, int group_size, int bits>
     uint3 tid [[threadgroup_position_in_grid]],
     uint simd_gid [[simdgroup_index_in_threadgroup]],
     uint simd_lid [[thread_index_in_simdgroup]]) {
+  int M = x_shape[x_batch_ndims];
   adjust_matrix_offsets<T>(
       x,
       w,
@@ -1836,7 +1844,7 @@ template <typename T, int group_size, int bits>
       lhs_indices,
       rhs_indices,
       y,
-      out_vec_size,
+      out_vec_size * M,
       batch_ndims,
       batch_shape,
       lhs_strides,

python/tests/test_quantized.py

@@ -212,11 +212,12 @@ def test_small_matrix(self):
                 w_hat = mx.dequantize(w_q, scales, biases)
 
                 # Test qmv
-                x = mx.random.normal(shape=(3, 1, 256))
-                y_q = mx.quantized_matmul(x, w_q, scales, biases, transpose=True)
-                y_hat = x @ mx.swapaxes(w_hat, -1, -2)
-                self.assertEqual(y_q.shape, y_hat.shape)
-                self.assertLess((y_q - y_hat).abs().max(), 1e-3)
+                for shape in [(3, 1, 256), (3, 4, 256)]:
+                    x = mx.random.normal(shape=shape)
+                    y_q = mx.quantized_matmul(x, w_q, scales, biases, transpose=True)
+                    y_hat = x @ mx.swapaxes(w_hat, -1, -2)
+                    self.assertEqual(y_q.shape, y_hat.shape)
+                    self.assertLess((y_q - y_hat).abs().max(), 1e-3)
 
                 # Test qmm_t
                 x = mx.random.normal(shape=(3, 10, 256))