Fix incorrect reduction for small kernels

SanityRemnants · SanityRemnants · commit 59a498842a82 · 2025-12-09T14:14:29.000+01:00
Ensures num_items is recalculated after updating group_width when num_items is less than max_sg_sz, preventing incorrect parallelism configuration.
diff --git a/src/ATen/native/xpu/sycl/Reduce.h b/src/ATen/native/xpu/sycl/Reduce.h
@@ -259,7 +259,10 @@ struct ReduceConfig {
     num_items = group_width * group_height;
 
     if (num_items < max_sg_sz)
+    {
       group_width = max_sg_sz;
+      num_items = group_width * group_height;
+    }
   }
 
   int split_input(int parallelism) {

Original file line number	Diff line number	Diff line change
`@@ -259,7 +259,10 @@ struct ReduceConfig {`
`259`	`259`	`num_items = group_width * group_height;`
`260`	`260`
`261`	`261`	`if (num_items < max_sg_sz)`
	`262`	`+ {`
`262`	`263`	`group_width = max_sg_sz;`
	`264`	`+ num_items = group_width * group_height;`
	`265`	`+ }`
`263`	`266`	`}`
`264`	`267`
`265`	`268`	`int split_input(int parallelism) {`