charmplusplus · ritvikrao · Jun 2, 2026
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -107,7 +107,7 @@ else()
 endif()
 
 # Build options
-set(NETWORK "netlrts" CACHE STRING "Target network layer, can be one of mpi,multicore,netlrts,gni,ofi,pami,pamilrts,ucx,verbs")
+set(NETWORK "netlrts" CACHE STRING "Target network layer, can be one of mpi,multicore,netlrts,reconverse,gni,ofi,pami,pamilrts,ucx,verbs")
 set(TARGET "charm++" CACHE STRING "Target build type, can be one of charm++,AMPI,LIBS,charm4py,ChaNGa,everylb,all-test")
 set(ARCH "" CACHE STRING "Target architecture, can be one of i386,x86_64,arm7,arm8,ppc64le") # By default, detect arch we are running on.
 
@@ -266,6 +266,10 @@ else()
   set(CMK_TASKQUEUE 0)
 endif()
 
+if(${NETWORK} STREQUAL "reconverse")
+  set(RECONVERSE ON)
+endif()
+
 if(${RECONVERSE})
   set(CMK_RECONVERSE 1)
 else()
@@ -290,8 +294,10 @@ else()
   set(CMK_SMP 0)
 endif()
 
-if(${NETWORK} STREQUAL "multicore")
+if(${NETWORK} STREQUAL "multicore" OR ${NETWORK} STREQUAL "reconverse")
   set(CMK_SMP 1)
+endif()
+if(${NETWORK} STREQUAL "multicore")
   set(CMK_MULTICORE 1)
 else()
   set(CMK_MULTICORE 0)
@@ -327,7 +333,7 @@ IF(JPEG_FOUND)
   set(CMK_USE_LIBJPEG 1)
 ENDIF()
 
-if(NETWORK STREQUAL "pami")
+if(NETWORK STREQUAL "pami" OR NETWORK STREQUAL "reconverse")
   set(CMK_USE_LRTS 0)
 else()
   set(CMK_USE_LRTS 1)
@@ -786,7 +792,9 @@ if(CMK_COMPILER STREQUAL "msvc")
 endif()
 
 # Header files
-configure_file(src/arch/${GDIR}/conv-common.h                include/ COPYONLY)
+if(EXISTS src/arch/${GDIR}/conv-common.h)
+  configure_file(src/arch/${GDIR}/conv-common.h                include/ COPYONLY)
+endif()
 if(EXISTS src/arch/${GDIR}/conv-common.sh)
   configure_file(src/arch/${GDIR}/conv-common.sh               include/ COPYONLY)
 endif()
@@ -880,7 +888,9 @@ include(cmake/hwloc.cmake)
 
 # Converse
 include(cmake/converse.cmake)
-add_subdirectory(src/QuickThreads)
+if(NOT RECONVERSE)
+  add_subdirectory(src/QuickThreads)
+endif()
 # add_subdirectory(src/util/boost-context)
 # add_subdirectory(src/conv-core)
 
@@ -1019,9 +1029,11 @@ else()
   if(RECONVERSE)
     target_link_libraries(ckhello PRIVATE reconverse)
   endif()
-  add_dependencies(ckhello ck ckqt conv-static
-    converse ckmain
-    moduleNDMeshStreamer modulecompletion)
+  set(ckhello_deps ck converse ckmain moduleNDMeshStreamer modulecompletion)
+  if(NOT RECONVERSE)
+    list(APPEND ckhello_deps ckqt conv-static)
+  endif()
+  add_dependencies(ckhello ${ckhello_deps})
 endif()
 
 # Create conv-mach-opt.sh

diff --git a/README.md b/README.md
@@ -92,19 +92,21 @@ of the `<options>` below.
 
 (Note: this isn't a complete list.  Run `./build` for a complete listing)
 
-| Charm++ Version           | OS      | Communication | Default Compiler                      |
-|---------------------------|---------|---------------|---------------------------------------|
-| `netlrts-linux-x86_64`    | Linux   | UDP           | GNU compiler                          |
-| `netlrts-darwin-x86_64`   | macOS   | UDP           | Clang C++ compiler                    |
-| `netlrts-win-x86_64`      | Windows | UDP           | MS Visual C++                         |
-| `mpi-linux-x86_64`        | Linux   | MPI           | GNU compiler                          |
-| `multicore-linux-x86_64`  | Linux   | Shared memory | GNU compiler                          |
-| `multicore-darwin-x86_64` | macOS   | Shared memory | Clang C++ compiler                    |
-| `gni-crayxc`              | Linux   | GNI           | CC (whatever PrgEnv module is loaded) |
-| `gni-crayxe`              | Linux   | GNI           | CC (whatever PrgEnv module is loaded) |
-| `verbs-linux-x86_64`      | Linux   | IB Verbs      | GNU compiler                          |
-| `ofi-linux-x86_64`        | Linux   | OFI           | GNU compiler                          |
-| `ucx-linux-x86_64`        | Linux   | UCX           | GNU compiler                          |
+| Charm++ Version               | OS      | Communication  | Default Compiler                      |
+|-------------------------------|---------|----------------|---------------------------------------|
+| `netlrts-linux-x86_64`        | Linux   | UDP            | GNU compiler                          |
+| `netlrts-darwin-x86_64`       | macOS   | UDP            | Clang C++ compiler                    |
+| `netlrts-win-x86_64`          | Windows | UDP            | MS Visual C++                         |
+| `mpi-linux-x86_64`            | Linux   | MPI            | GNU compiler                          |
+| `multicore-linux-x86_64`      | Linux   | Shared memory  | GNU compiler                          |
+| `multicore-darwin-x86_64`     | macOS   | Shared memory  | Clang C++ compiler                    |
+| `reconverse-linux-x86_64`     | Linux   | LCI/LCW        | GNU compiler                          |
+| `reconverse-darwin-arm8`      | macOS   | LCI/LCW        | Clang C++ compiler                    |
+| `gni-crayxc`                  | Linux   | GNI            | CC (whatever PrgEnv module is loaded) |
+| `gni-crayxe`                  | Linux   | GNI            | CC (whatever PrgEnv module is loaded) |
+| `verbs-linux-x86_64`          | Linux   | IB Verbs       | GNU compiler                          |
+| `ofi-linux-x86_64`            | Linux   | OFI            | GNU compiler                          |
+| `ucx-linux-x86_64`            | Linux   | UCX            | GNU compiler                          |
 
 
 To choose `<version>`, your choice is determined by two options:
@@ -119,6 +121,12 @@ To choose `<version>`, your choice is determined by two options:
     but performance is often worse than using the machine's direct calls referenced above.
     * `multicore-`: Charm++ communicates using shared memory within a single node. A version of
     Charm++ built with this option will not run on more than a single node.
+    * `reconverse-`: Charm++ uses the Reconverse communication layer backed by LCI or LCW.
+    Reconverse is an alternative to the standard Converse layer and is always built in SMP mode
+    (there is no separate communication thread; LCI handles progress internally). It supports
+    single-node runs with no backend, multi-node runs via LCI (recommended for performance),
+    or multi-node runs via LCW (an MPI-based fallback). See
+    [Building with Reconverse](#building-with-reconverse) below.
 
 
 2. Your operating system/architecture:
@@ -182,6 +190,67 @@ for more information:
       Supported options: common cuda flang gfortran ifort local nolb omp ooc papi perftools persistent pgf90 pxshm smp syncft sysvshm tcp tsan
 
 
+## Building with Reconverse
+
+The `reconverse-` triplets are always SMP (no `-smp` suffix needed) and always
+enable the Reconverse communication layer. They are built with the standard
+`./build` script like any other version.
+
+### Quick start
+
+On Linux x86\_64:
+
+    $ ./build charm++ reconverse-linux-x86_64
+
+On macOS ARM64:
+
+    $ ./build charm++ reconverse-darwin-arm8
+
+This fetches Reconverse (and optionally LCI) from their upstream repositories
+and builds everything in a single step. The resulting build directory is named
+after the triplet (e.g. `reconverse-linux-x86_64/`).
+
+### Communication backends
+
+Reconverse supports three backends, selected at runtime:
+
+* **None** (default for single-process runs): no inter-node communication library
+  is required. This is suitable for development and testing on a single machine.
+* **LCI** (recommended for multi-node): a lightweight communication interface
+  designed for low-latency active-message communication. LCI is fetched and
+  built automatically unless a pre-installed copy is available.
+* **LCW**: an MPI-based wrapper backend. Useful as a fallback on systems where
+  LCI is not available or supported.
+
+At runtime, the backend is selected automatically based on what was compiled in.
+To force a specific backend, pass `+backend lci` or `+backend lcw` on the
+command line.
+
+### Fetching LCI automatically
+
+LCI is fetched by default for reconverse triplets. To use a pre-installed copy
+of LCI instead, set `LCI_ROOT` in your environment before building:
+
+    $ LCI_ROOT=/path/to/lci ./build charm++ reconverse-linux-x86_64
+
+To fetch a specific Reconverse tag or use a local checkout:
+
+    $ ./build charm++ reconverse-linux-x86_64 --with-fetch-reconverse-tag=v1.2.3
+    $ ./build charm++ reconverse-linux-x86_64 --with-fetch-reconverse-dir=/path/to/reconverse
+
+### Build options
+
+The same options available for other versions work with reconverse builds:
+
+* `-j<N>` — parallel build with N jobs (e.g. `-j8`)
+* `--with-production` — enable production optimizations
+* `--enable-tracing` — enable Projections performance tracing
+* `--destination=<dir>` — place the build in a custom directory
+
+For example:
+
+    $ ./build charm++ reconverse-linux-x86_64 -j8 --with-production
+
 ## Building the Source
 
 If you have downloaded a binary version of Charm++, you can skip

diff --git a/buildcmake b/buildcmake
@@ -608,6 +608,14 @@ fi
 
 my_os=$(echo "$actual_triplet" | cut -d '-' -f2)
 
+# reconverse network type implies reconverse communication layer and inherent SMP.
+# CMK_SMP is forced to 1 by CMakeLists.txt for reconverse; we do not pass -DSMP=1
+# here because that would trigger the opt-file loop to source conv-mach-smp.sh,
+# which does not exist for reconverse (SMP flags are baked into conv-mach.h directly).
+if [[ $opt_network == "reconverse" ]]; then
+  opt_reconverse=1
+fi
+
 if [[ $opt_network == "mpi" && $my_os == "win" ]]; then
   echo "Warning: CMake build is not supported with MPI on Windows, running ./buildold instead."
   sleep 2

diff --git a/cmake/converse.cmake b/cmake/converse.cmake
@@ -279,12 +279,14 @@ endforeach()
 # target_include_directories(converse PRIVATE src/util) # for sockRoutines.C
 # target_include_directories(converse PRIVATE src/conv-core src/util/topomanager src/ck-ldb src/ck-perf src/ck-cp)
 
-# conv-static
-add_library(conv-static OBJECT src/conv-core/conv-static.c)
-add_dependencies(reconverse conv-static)
-add_dependencies(charm_cxx_utils conv-static)
-add_custom_command(TARGET charm_cxx_utils
-    POST_BUILD
-    COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/conv-static.dir/src/conv-core/conv-static.c.o ${CMAKE_BINARY_DIR}/lib/conv-static.o
-    VERBATIM
-)
+# conv-static: not needed for reconverse builds (reconverse provides its own converse layer)
+if(NOT RECONVERSE)
+  add_library(conv-static OBJECT src/conv-core/conv-static.c)
+  add_dependencies(reconverse conv-static)
+  add_dependencies(charm_cxx_utils conv-static)
+  add_custom_command(TARGET charm_cxx_utils
+      POST_BUILD
+      COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/conv-static.dir/src/conv-core/conv-static.c.o ${CMAKE_BINARY_DIR}/lib/conv-static.o
+      VERBATIM
+  )
+endif()
diff --git a/src/arch/reconverse-darwin-arm8/conv-mach.h b/src/arch/reconverse-darwin-arm8/conv-mach.h
@@ -0,0 +1,68 @@
+#ifndef _CONV_MACH_H
+#define _CONV_MACH_H
+
+#define CMK_ARM                                            1
+#define CMK_64BIT                                          1
+#define CMK_SMP                                            1
+
+#undef CMK_IMMEDIATE_MSG
+#define CMK_IMMEDIATE_MSG                                  0
+
+#define CMK_ASYNC_NOT_NEEDED                               1
+#define CMK_ASYNC_USE_FIOASYNC_AND_FIOSETOWN               0
+#define CMK_ASYNC_USE_FIOASYNC_AND_SIOCSPGRP               0
+#define CMK_ASYNC_USE_FIOSSAIOSTAT_AND_FIOSSAIOOWN         0
+#define CMK_ASYNC_USE_F_SETFL_AND_F_SETOWN                 1
+
+#define CMK_GETPAGESIZE_AVAILABLE                          0
+
+#define CMK_MALLOC_USE_GNU_MALLOC                          0
+#define CMK_MALLOC_USE_OS_BUILTIN                          1
+#define CMK_MALLOC_USE_GNUOLD_MALLOC                       0
+
+#undef CMK_MEMORY_BUILD_GNU_HOOKS
+#define CMK_MEMORY_BUILD_GNU_HOOKS                         0
+#define CMK_MEMORY_PAGESIZE                                4096
+#define CMK_MEMORY_PROTECTABLE                             0
+
+
+#define CMK_SSH_IS_A_COMMAND                               1
+#define CMK_SSH_NOT_NEEDED                                 0
+
+#define CMK_SHARED_VARS_UNAVAILABLE                        0
+#define CMK_SHARED_VARS_POSIX_THREADS_SMP                  1
+
+#define CMK_THREADS_USE_CONTEXT                            0
+#define CMK_THREADS_USE_JCONTEXT                           0
+#define CMK_THREADS_USE_FCONTEXT                           1
+#define CMK_THREADS_USE_PTHREADS                           0
+#define CMK_THREADS_ARE_WIN32_FIBERS                       0
+
+#define CMK_SIGNAL_NOT_NEEDED                              1
+#define CMK_SIGNAL_USE_SIGACTION                           0
+#define CMK_SIGNAL_USE_SIGACTION_WITH_RESTART              0
+
+#define CMK_THREADS_REQUIRE_NO_CPV                         0
+#define CMK_THREADS_COPY_STACK                             0
+
+#define CMK_TIMER_USE_GETRUSAGE                            1
+#define CMK_TIMER_USE_SPECIAL                              0
+#define CMK_TIMER_USE_TIMES                                0
+
+
+#define CMK_DEBUG_MODE					   0
+#define CMK_WEB_MODE                                       1
+
+#define CMK_LBDB_ON					   1
+
+#define CMK_STACKSIZE_DEFAULT				   65536
+
+#define CMK_USE_KQUEUE                                     1
+
+#define CMK_NOT_USE_TLS_THREAD                             1
+
+/* #define CMK_PCQUEUE_LOCK                                   1 */
+
+#define CMK_CONVERSE_MPI                                   0
+
+#endif
diff --git a/src/arch/reconverse-darwin-arm8/conv-mach.sh b/src/arch/reconverse-darwin-arm8/conv-mach.sh
@@ -0,0 +1,10 @@
+. $CHARMINC/cc-clang.sh
+. $CHARMINC/conv-mach-darwin.sh
+
+CMK_DEFS="$CMK_DEFS -D_REENTRANT"
+
+# Reconverse provides its own threading; remove the QuickThreads library
+# injected by conv-mach-darwin.sh
+CMK_LIBS="${CMK_LIBS//-lckqt/}"
+
+CMK_SMP="1"
diff --git a/src/arch/reconverse-linux-x86_64/conv-mach.h b/src/arch/reconverse-linux-x86_64/conv-mach.h
@@ -0,0 +1,62 @@
+#ifndef _CONV_MACH_H
+#define _CONV_MACH_H
+
+#define CMK_AMD64					   1
+#define CMK_64BIT    1
+#define CMK_SMP						   1
+
+#undef CMK_IMMEDIATE_MSG
+#define CMK_IMMEDIATE_MSG                                  0
+
+#define CMK_ASYNC_NOT_NEEDED                               1
+#define CMK_ASYNC_USE_FIOASYNC_AND_FIOSETOWN               0
+#define CMK_ASYNC_USE_FIOASYNC_AND_SIOCSPGRP               0
+#define CMK_ASYNC_USE_FIOSSAIOSTAT_AND_FIOSSAIOOWN         0
+#define CMK_ASYNC_USE_F_SETFL_AND_F_SETOWN                 0
+
+#define CMK_DLL_CC  "g++ -shared -O3 -o "
+
+#define CMK_GETPAGESIZE_AVAILABLE                          1
+
+#define CMK_MALLOC_USE_GNU_MALLOC                          0
+#define CMK_MALLOC_USE_OS_BUILTIN                          1
+
+#define CMK_MEMORY_PAGESIZE                                4096
+#define CMK_MEMORY_PROTECTABLE                             0
+
+
+#define CMK_SSH_IS_A_COMMAND                               1
+#define CMK_SSH_NOT_NEEDED                                 0
+
+#define CMK_SHARED_VARS_UNAVAILABLE                        0
+#define CMK_SHARED_VARS_POSIX_THREADS_SMP                  1
+
+#define CMK_THREADS_USE_CONTEXT                            0
+#define CMK_THREADS_USE_FCONTEXT                           1
+#define CMK_THREADS_USE_PTHREADS                           0
+#define CMK_THREADS_ARE_WIN32_FIBERS                       0
+
+#define CMK_SIGNAL_NOT_NEEDED                              1
+#define CMK_SIGNAL_USE_SIGACTION                           0
+#define CMK_SIGNAL_USE_SIGACTION_WITH_RESTART              0
+
+#define CMK_THREADS_REQUIRE_NO_CPV                         0
+#define CMK_THREADS_COPY_STACK                             0
+
+#define CMK_TIMER_USE_RDTSC                                0
+#define CMK_TIMER_USE_GETRUSAGE                            1
+#define CMK_TIMER_USE_SPECIAL                              0
+#define CMK_TIMER_USE_TIMES                                0
+
+
+#define CMK_WHEN_PROCESSOR_IDLE_BUSYWAIT                   0
+#define CMK_WHEN_PROCESSOR_IDLE_USLEEP                     1
+
+#define CMK_DEBUG_MODE					   0
+#define CMK_WEB_MODE                                       1
+
+#define CMK_LBDB_ON					   1
+
+#define CMK_CONVERSE_MPI                                   0
+
+#endif
diff --git a/src/arch/reconverse-linux-x86_64/conv-mach.sh b/src/arch/reconverse-linux-x86_64/conv-mach.sh
@@ -0,0 +1,10 @@
+. $CHARMINC/cc-gcc.sh
+
+CMK_DEFS="$CMK_DEFS -D_REENTRANT"
+
+CMK_XIOPTS=''
+CMK_LIBS="-lpthread $CMK_LIBS"
+
+CMK_QT='generic64-light'
+
+CMK_SMP='1'
diff --git a/src/libs/ck-libs/metis/GKlib/GKlib.h b/src/libs/ck-libs/metis/GKlib/GKlib.h
@@ -11,7 +11,9 @@
 #ifndef _GKLIB_H_
 #define _GKLIB_H_ 1
 
-#include "conv-config.h"
+//#include "conv-config.h"
+#include "charm-config.h"
+#include "converse.h"
 
 #define GKMSPACE