GH-200 Unified Memory Support (#470)

* bruh

* Had to pass flag as a linker option too

* Okay, looks like it works

Just remember to add docs next

* Fix formatting, add docs

* remove tab character

til 'or' also has the semantics of <|>

Author: AiredaleDev

CMakeLists.txt

@@ -16,15 +16,16 @@ project(MFC LANGUAGES C CXX Fortran)
 
 # Build options exposed to users and their default values.
 
-option(MFC_MPI           "Build with MPI"       ON)
-option(MFC_OpenACC       "Build with OpenACC"  OFF)
-option(MFC_GCov          "Build with GCov"     OFF)
-option(MFC_PRE_PROCESS   "Build pre_process"   OFF)
-option(MFC_SIMULATION    "Build simulation"    OFF)
-option(MFC_POST_PROCESS  "Build post_process"  OFF)
-option(MFC_SYSCHECK      "Build syscheck"      OFF)
-option(MFC_DOCUMENTATION "Build documentation" OFF)
-option(MFC_ALL           "Build everything"    OFF)
+option(MFC_MPI           "Build with MPI"                                     ON)
+option(MFC_OpenACC       "Build with OpenACC"                                OFF)
+option(MFC_GCov          "Build with GCov"                                   OFF)
+option(MFC_Unified       "Build with unified CPU & GPU memory (GH-200 only)" OFF)
+option(MFC_PRE_PROCESS   "Build pre_process"                                 OFF)
+option(MFC_SIMULATION    "Build simulation"                                  OFF)
+option(MFC_POST_PROCESS  "Build post_process"                                OFF)
+option(MFC_SYSCHECK      "Build syscheck"                                    OFF)
+option(MFC_DOCUMENTATION "Build documentation"                               OFF)
+option(MFC_ALL           "Build everything"                                  OFF)
 
 if (MFC_ALL)
     set(MFC_PRE_PROCESS   ON FORCE)
@@ -454,6 +455,17 @@ function(MFC_SETUP_TARGET)
                 PRIVATE -gpu=keep,ptxinfo,lineinfo
             )
 
+            # GH-200 Unified Memory Support
+            if (MFC_Unified)
+                target_compile_options(${ARGS_TARGET}
+                    PRIVATE -gpu=unified
+                )
+                # "This option must appear in both the compile and link lines" -- NVHPC Docs
+                target_link_options(${ARGS_TARGET}
+                    PRIVATE -gpu=unified
+                )
+            endif()
+
             if (CMAKE_BUILD_TYPE STREQUAL "Debug")
                 target_compile_options(${ARGS_TARGET}
                     PRIVATE -gpu=autocompare,debug

docs/documentation/getting-started.md

@@ -172,12 +172,13 @@ session exit.
 
 MFC can be built with support for various (compile-time) features:
 
-| Feature   | Enable    | Disable      | Default | Description                                                     |
-| :-------: | :-------: | :----------: | :-----: | --------------------------------------------------------------- |
-| **MPI**   | `--mpi`   | `--no-mpi`   | On      | Lets MFC run on multiple processors (and nodes) simultaneously. |
-| **GPU**   | `--gpu`   | `--no-gpu`   | Off     | Enables GPU acceleration via OpenACC.                           |
-| **Debug** | `--debug` | `--no-debug` | Off     | Requests the compiler build MFC in debug mode.                  |
-| **GCov**  | `--gcov`  | `--no-gcov`  | Off     | Builds MFC with coverage flags on.                              |
+| Feature            | Enable      | Disable        | Default | Description                                                     |
+| :----------------: | :---------: | :------------: | :-----: | --------------------------------------------------------------- |
+| **MPI**            | `--mpi`     | `--no-mpi`     | On      | Lets MFC run on multiple processors (and nodes) simultaneously. |
+| **GPU**            | `--gpu`     | `--no-gpu`     | Off     | Enables GPU acceleration via OpenACC.                           |
+| **Debug**          | `--debug`   | `--no-debug`   | Off     | Requests the compiler build MFC in debug mode.                  |
+| **GCov**           | `--gcov`    | `--no-gcov`    | Off     | Builds MFC with coverage flags on.                              |
+| **Unified Memory** | `--unified` | `--no-unified` | Off     | Builds MFC with unified CPU/GPU memory (GH-200 superchip only)  |
 
 _⚠️ The `--gpu` option requires that your compiler supports OpenACC for Fortran for your target GPU architecture._
 

src/simulation/m_riemann_solvers.fpp

@@ -1542,6 +1542,7 @@ contains
                                 pi_inf_L = 0d0
                                 qv_L = 0d0
 
+                                ! Retain this in the refactor
                                 if (mpp_lim .and. (num_fluids > 2)) then
                                     !$acc loop seq
                                     do i = 1, num_fluids
@@ -2005,6 +2006,8 @@ contains
                                 alpha_L_sum = 0d0
                                 alpha_R_sum = 0d0
 
+                                ! Change this by splitting it into the cases
+                                ! present in the bubbles
                                 if (mpp_lim) then
                                     !$acc loop seq
                                     do i = 1, num_fluids

toolchain/main.py

@@ -31,8 +31,9 @@ def __print_greeting():
     ]
 
     for a, b in itertools.zip_longest(MFC_LOGO_LINES, MFC_SIDEBAR_LINES):
+        a = a or ''
         lhs = a.ljust(max_logo_line_length)
-        rhs = b if b is not None else ''
+        rhs = b or ''
         cons.print(
             f"[bold]{lhs}[/bold] | {rhs}",
             highlight=False

toolchain/mfc/build.py

@@ -142,9 +142,10 @@ def configure(self, case: input.MFCInputFile):
             flags.append('--debug-find')
 
         if not self.isDependency:
-            flags.append(f"-DMFC_MPI={    'ON' if ARG('mpi')  else 'OFF'}")
-            flags.append(f"-DMFC_OpenACC={'ON' if ARG('gpu')  else 'OFF'}")
+            flags.append(f"-DMFC_MPI={    'ON' if ARG('mpi') else 'OFF'}")
+            flags.append(f"-DMFC_OpenACC={'ON' if ARG('gpu') else 'OFF'}")
             flags.append(f"-DMFC_GCov={   'ON' if ARG('gcov') else 'OFF'}")
+            flags.append(f"-DMFC_Unified={'ON' if ARG('unified') else 'OFF'}")
 
         command = ["cmake"] + flags + ["-S", cmake_dirpath, "-B", build_dirpath]
 

toolchain/mfc/state.py

@@ -3,10 +3,11 @@
 
 @dataclasses.dataclass
 class MFCConfig:
-    mpi:   bool = True
-    gpu:   bool = False
-    debug: bool = False
-    gcov:  bool = False
+    mpi:     bool = True
+    gpu:     bool = False
+    debug:   bool = False
+    gcov:    bool = False
+    unified: bool = False
 
     @staticmethod
     def from_dict(d: dict):
@@ -24,7 +25,7 @@ def items(self) -> typing.List[typing.Tuple[str, bool]]:
 
     def make_options(self) -> typing.List[str]:
         """ Returns a list of options that could be passed to mfc.sh again.
-            Example: --no-debug --mpi --no-gpu --no-gcov"""
+            Example: --no-debug --mpi --no-gpu --no-gcov --no-unified"""
         return [ f"--{'no-' if not v else ''}{k}" for k, v in self.items() ]
 
     def make_slug(self) -> str:
@@ -41,7 +42,7 @@ def __eq__(self, other) -> bool:
         return True
 
     def __str__(self) -> str:
-        """ Returns a string like "mpi=No & gpu=No & debug=No & gcov=No" """
+        """ Returns a string like "mpi=No & gpu=No & debug=No & gcov=No & unified=No" """
 
         return ' & '.join([ f"{k}={'Yes' if v else 'No'}" for k, v in self.items() ])