scr: require dtcmp, switch from /tmp to /dev/shm (#22073)

1 files changed, 16 insertions, 4 deletions

diff --git a/var/spack/repos/builtin/packages/scr/package.py b/var/spack/repos/builtin/packages/scr/package.py
index 6821f8c5ed..28513e5ce6 100644
--- a/var/spack/repos/builtin/packages/scr/package.py
+++ b/var/spack/repos/builtin/packages/scr/package.py
@@ -7,6 +7,9 @@ from spack import *
 
 import os
 
+# to get system platform type
+import sys
+
 
 class Scr(CMakePackage):
     """SCR caches checkpoint data in storage on the compute nodes of a
@@ -43,10 +46,15 @@ class Scr(CMakePackage):
     depends_on('filo', when="@3:")
     depends_on('spath', when="@3:")
 
+    # DTCMP is an optional dependency up until 3.x
     variant('dtcmp', default=True,
             description="Build with DTCMP. "
             "Necessary to enable user directory naming at runtime")
-    depends_on('dtcmp', when="+dtcmp")
+    depends_on('dtcmp', when="@:2.999 +dtcmp")
+
+    # DTCMP is a required dependency with 3.x and later
+    conflicts('~dtcmp', when="@3:", msg="<SCR> DTCMP required for versions >=3")
+    depends_on('dtcmp', when="@3:")
 
     variant('libyogrt', default=True,
             description="Build SCR with libyogrt for get_time_remaining.")
@@ -83,9 +91,13 @@ class Scr(CMakePackage):
             multi=False,
             description='File locking style for SCR.')
 
-    variant('cache_base', default='/tmp',
-            description='Compile time default location for checkpoint cache.')
-    variant('cntl_base', default='/tmp',
+    # The default cache and control directories should be placed in tmpfs if available.
+    # On Linux, /dev/shm is a common tmpfs location.  Other platforms, like macOS,
+    # do not define a common tmpfs location, so /tmp is the next best option.
+    platform_tmp_default = '/dev/shm' if sys.platform == 'linux' else '/tmp'
+    variant('cache_base', default=platform_tmp_default,
+            description='Compile time default location for cache directory.')
+    variant('cntl_base', default=platform_tmp_default,
             description='Compile time default location for control directory.')
 
     def get_abs_path_rel_prefix(self, path):