namd: add compile options for ROCm (spack#45553)

* namd:add compile options for ROCm
* Combine --rocm-prefix and its value in a single opts.extend call to ensure they remain ordered correctly and improve code robustness.
* Standardize the code and add ROCm conflicts
* add single_node_gpu conflict

---------

Co-authored-by: U-PALLAS\boudaoud <[email protected]>

var/spack/repos/builtin/packages/namd/package.py

@@ -12,7 +12,7 @@
 from spack.package import *
 
 
-class Namd(MakefilePackage, CudaPackage):
+class Namd(MakefilePackage, CudaPackage, ROCmPackage):
     """NAMD is a parallel molecular dynamics code designed for
     high-performance simulation of large biomolecular systems."""
 
@@ -104,6 +104,9 @@ class Namd(MakefilePackage, CudaPackage):
     depends_on("python", when="interface=python")
 
     conflicts("+avxtiles", when="@:2.14,3:", msg="AVXTiles algorithm requires NAMD 2.15")
+    conflicts("+rocm", when="~single_node_gpu")
+    conflicts("+rocm", when="+cuda", msg="NAMD supports only one GPU backend at a time")
+    conflicts("+single_node_gpu", when="~cuda~rocm")
 
     # https://www.ks.uiuc.edu/Research/namd/2.12/features.html
     # https://www.ks.uiuc.edu/Research/namd/2.13/features.html
@@ -294,6 +297,14 @@ def edit(self, spec, prefix):
             if "+single_node_gpu" in spec:
                 opts.extend(["--with-single-node-cuda"])
 
+        if "+rocm" in spec:
+            self._copy_arch_file("hip")
+            opts.append("--with-hip")
+            opts.extend(["--rocm-prefix", os.environ["ROCM_PATH"]])
+
+            if "+single_node_gpu" in spec:
+                opts.extend(["--with-single-node-hip"])
+
         config = Executable("./config")
 
         config(self.build_directory, *opts)