diff --git a/src/correlation/vk.rs b/src/correlation/vk.rs
index ed81ce7..8968a9e 100644
--- a/src/correlation/vk.rs
+++ b/src/correlation/vk.rs
@@ -1,4 +1,4 @@
-use std::{collections::HashMap, error, ffi::CStr, fmt, slice, time::SystemTime};
+use std::{cmp::Ordering, collections::HashMap, error, ffi::CStr, fmt, slice, time::SystemTime};
 
 use ash::{prelude::VkResult, vk};
 use nalgebra::Matrix3;
@@ -906,7 +906,7 @@ impl Device {
     unsafe fn find_device(
         instance: &ash::Instance,
         max_buffer_size: usize,
-    ) -> Result<(vk::PhysicalDevice, &'static str, u32), Box<dyn error::Error>> {
+    ) -> Result<(vk::PhysicalDevice, String, u32), Box<dyn error::Error>> {
         let devices = instance.enumerate_physical_devices()?;
         let device = devices
             .iter()
@@ -923,16 +923,7 @@ impl Device {
                 let queue_index = Device::find_compute_queue(instance, device)?;
 
                 let device_name = CStr::from_ptr(props.device_name.as_ptr());
-                let device_name = device_name.to_str().unwrap();
-                println!(
-                    "Device {} type {} {}-{}-{}-{}",
-                    device_name,
-                    props.device_type.as_raw(),
-                    props.limits.max_push_constants_size,
-                    props.limits.max_bound_descriptor_sets,
-                    props.limits.max_storage_buffer_range,
-                    max_buffer_size
-                );
+                let device_name = String::from_utf8_lossy(device_name.to_bytes()).to_string();
                 // TODO: allow to specify a device name filter/regex?
                 let score = match props.device_type {
                     vk::PhysicalDeviceType::DISCRETE_GPU => 3,
@@ -941,24 +932,25 @@ impl Device {
                     _ => 0,
                 };
                 // Prefer real devices instead of dzn emulation.
-                let dzn_multiplier = if device_name
+                let is_dzn = device_name
                     .to_lowercase()
-                    .starts_with("microsoft direct3d12")
-                {
-                    1
-                } else {
-                    10
-                };
-                Some((device, device_name, queue_index, score * dzn_multiplier))
+                    .starts_with("microsoft direct3d12");
+                let score = (score, is_dzn);
+                Some((device, device_name, queue_index, score))
             })
-            .max_by_key(|(_device, _name, _queue_index, score)| *score);
-        let (device, name, queue_index) = if let Some((device, name, queue_index, _score)) = device
-        {
+            .max_by(|(_, _, _, a), (_, _, _, b)| {
+                if a.1 && !b.1 {
+                    return Ordering::Less;
+                } else if !a.1 && b.1 {
+                    return Ordering::Greater;
+                }
+                return a.0.cmp(&b.0);
+            });
+        let (device, name, queue_index) = if let Some((device, name, queue_index, score)) = device {
             (device, name, queue_index)
         } else {
             return Err(GpuError::new("Device not found").into());
         };
-        println!("selected device {}", name);
         Ok((device, name, queue_index))
     }
 
@@ -1009,6 +1001,7 @@ impl Device {
         let max_pixels = img1_pixels.max(img2_pixels);
         let mut buffers: Vec<Buffer> = vec![];
         let cleanup_err = |buffers: &[Buffer], err| {
+            println!("buffers count is {}", buffers.len());
             buffers.iter().for_each(|buffer| {
                 device.free_memory(buffer.buffer_memory, None);
                 device.destroy_buffer(buffer.buffer, None)