tuning: fix thread counts

Author: mdekstrand

src/lenskit/tuning/_search.py

@@ -217,6 +217,8 @@ def setup_harness(self):
 
         match self.spec.search.num_cpus:
             case "threads":
+                tune_cpus = paracfg.num_threads or 1
+            case "backend-threads":
                 tune_cpus = paracfg.num_backend_threads or 1
             case "all-threads":
                 tune_cpus = paracfg.total_threads

src/lenskit/tuning/spec.py

@@ -50,7 +50,7 @@ class SearchConfig(BaseModel):
     """
     The length of recommendation lists to use.
     """
-    num_cpus: int | Literal["threads", "all-threads"] = "threads"
+    num_cpus: int | Literal["threads", "backend-threads", "all-threads"] = "threads"
     """
     The number of CPUs to request from Ray Tune.
     """