explicit_threshold_cap regression diffs

[df7cb]

2.20 fails the tests here:

--- /home/myon/projects/postgresql/postgresql-hll/postgresql-hll/expected/explicit_threshold_cap.out	2026-05-27 10:05:41.000000000 +0200
+++ /home/myon/projects/postgresql/postgresql-hll/postgresql-hll/results/explicit_threshold_cap.out	2026-05-27 11:22:29.487065776 +0200
@@ -271,9 +271,9 @@
 -- Non-parallel baseline.
 SET max_parallel_workers_per_gather = 0;
 SELECT hll_cardinality(hll_union_agg(h)) AS card_serial FROM hll_parallel_test;
-    card_serial    
--------------------
- 999.7020724616214
+   card_serial    
+------------------
+ 999.702072461621
 (1 row)
 
 -- Force parallel execution to exercise hll_serialize/hll_deserialize.
@@ -282,9 +282,9 @@
 SET parallel_setup_cost = 0;
 SET min_parallel_table_scan_size = 0;
 SELECT hll_cardinality(hll_union_agg(h)) AS card_parallel FROM hll_parallel_test;
-   card_parallel   
--------------------
- 999.7020724616214
+  card_parallel   
+------------------
+ 999.702072461621
 (1 row)
 
 -- Reset.
### End 18 installcheck (FAILED with exit code 1) ###

[ihalatci]

Could you please share details on your environment?

[df7cb]

The problem originally happened on Debian unstable amd64, but the fix is required on all Debian and Ubuntu versions and all architectures (amd64 arm64 ppc64el loong64).