change for loop to transform_reduce

cpp/src/strings/convert/convert_durations.cu

@@ -20,6 +20,7 @@
 #include <strings/convert/utilities.cuh>
 #include <strings/utilities.cuh>
 
+#include <thrust/transform_reduce.h>
 #include <map>
 #include <rmm/device_uvector.hpp>
 #include <vector>
@@ -228,17 +229,20 @@ struct duration_to_string_size_fn {
     auto duration                   = d_durations.element<T>(idx);
     int32_t timeparts[DU_ARRAYSIZE] = {0};  // days, hours, minutes, seconds, subseconds(9)
     dissect_duration(duration.count(), timeparts, type);
-    size_type string_length{0};
-    for (auto i = 0; i < items_count; i++) {
-      format_item item = d_format_items[i];
-      if (item.item_type == format_char_type::literal)
-        string_length++;
-      else if (item.length != -1)
-        string_length += item.length;
-      else
-        string_length += format_length(item.value, timeparts);
-    }
-    return string_length;
+    return thrust::transform_reduce(
+      thrust::seq,
+      d_format_items,
+      d_format_items + items_count,
+      [this, &timeparts] __device__(format_item item) -> size_type {
+        if (item.item_type == format_char_type::literal)
+          return 1;
+        else if (item.length != -1)
+          return item.length;
+        else
+          return format_length(item.value, timeparts);
+      },
+      size_type{0},
+      thrust::maximum<size_type>());
   }
 };