[pve-devel] [PATCH proxmox-resource-scheduling] pve static: add one to avoid boosting tiny relative differences

[Fiona Ebner]

Only the relative difference for values between different alternatives
is relevant, meaning 0.002 vs 0.004 and 0.2 vs 0.4 will influence the
scoring in the same way. This is not really desirable, because values
closer to 1.0 indicate higher load and thus should influence the
scoring more than differences that are actually tiny, but big when
viewed as a relative difference.

To avoid the issue, simply add 1.0 to all values. Like that, 1.002 vs
1.004 will also be small when viewed as a relative difference.

Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
---
 src/pve_static.rs | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/pve_static.rs b/src/pve_static.rs
index 814d44f..d39614c 100644
--- a/src/pve_static.rs
+++ b/src/pve_static.rs
@@ -104,11 +104,13 @@ pub fn score_nodes_to_start_service(
                 squares_mem += new_mem.powi(2);
             }
 
+            // Add 1.0 to avoid boosting tiny differences: e.g. 0.004 is twice as much as 0.002, but
+            // 1.004 is only slightly more than 1.002.
             PveTopsisAlternative {
-                average_cpu: (squares_cpu / len as f64).sqrt(),
-                highest_cpu,
-                average_memory: (squares_mem / len as f64).sqrt(),
-                highest_memory: highest_mem,
+                average_cpu: 1.0 + (squares_cpu / len as f64).sqrt(),
+                highest_cpu: 1.0 + highest_cpu,
+                average_memory: 1.0 + (squares_mem / len as f64).sqrt(),
+                highest_memory: 1.0 + highest_mem,
             }
             .into()
         })
-- 
2.30.2