Do not default to n1-standard-4 if cpu or ram is specified

PiperOrigin-RevId: 449887413
Change-Id: I14d72ef8cc98d7cad84b8ac730634f59b4f4a5aa
GitOrigin-RevId: dbfca7713bb4e297bd1a14ff486a0c2e86d9a634

xmanager/cloud/vertex.py

@@ -341,7 +341,9 @@ def launch(experiment_title: str, work_unit_name: str,
 
 def cpu_ram_to_machine_type(cpu: Optional[int], ram: Optional[int]) -> str:
   """Convert a cpu and memory spec into a machine type."""
-  if cpu is None or ram is None:
+  cpu = cpu or 0
+  ram = ram or 0
+  if cpu + ram == 0:
     return 'n1-standard-4'
 
   optimal_machine_type = ''

xmanager/cloud/vertex_test.py

@@ -170,10 +170,17 @@ def test_cpu_ram_to_machine_type_highmem(self):
     self.assertEqual('n1-highmem-64',
                      vertex.cpu_ram_to_machine_type(1, 415 * xm.GiB))
 
+  def test_cpu_ram_to_machine_type_mem_only(self):
+    self.assertEqual('n1-highmem-64',
+                     vertex.cpu_ram_to_machine_type(None, 415 * xm.GiB))
+
   def test_cpu_ram_to_machine_type_highcpu(self):
     self.assertEqual('n1-highcpu-64',
                      vertex.cpu_ram_to_machine_type(63, 1 * xm.GiB))
 
+  def test_cpu_ram_to_machine_type_cpu_only(self):
+    self.assertEqual('n1-highcpu-64', vertex.cpu_ram_to_machine_type(63, None))
+
   def test_cpu_ram_to_machine_type_too_high(self):
     with self.assertRaises(ValueError):
       vertex.cpu_ram_to_machine_type(1000, 1000)