C++ and C/Fortran APIs¶

C++¶

melissa::init(const std::string& node_name, MPI_Comm comm)¶

Initializes the Melissa API context and registers a node. This is a collective MPI operation that must be called by all ranks before any data can be transmitted via melissa::send().

Initialization consists of two stages:

1. Global lifecycle setup (first call only) Initializes the Melissa API context and registers a node. This is a collective MPI operation that must be called by all ranks before any data can be transmitted via melissa::send().

Initialization consists of two stages:

1. Global lifecycle setup (first call only)

   • Establishes the connection with the Melissa server.
   • Initializes global runtime structures.

2. Node channel registration (every call)

   • Creates and tracks a communication channel for the specified node.

Parameters¶

• node_name — Unique identification string for the data node.

• comm — MPI communicator governing the simulation ranks.

  • Establishes the connection with the Melissa server.
  • Initializes global runtime structures.

• Node channel registration (every call)

  • Creates and tracks a communication channel for the specified node.

Parameters¶

• node_name — Unique identification string for the data node.
• comm — MPI communicator governing the simulation ranks.

melissa::send(const std::string& node_name, conduit::Node& payload)¶

Transmits a structured Conduit node payload to the Melissa server.

This is a collective operation across the MPI communicator. All ranks must call this function, but aggregation and transmission are handled by Rank 0.

Supported payload handling:

• Homogeneous leaf arrays are concatenated into a single linear array.
• Complex or hierarchical nodes are stored under rank-specific keys such as r0/, r1/, allowing server-side consolidation.

Parameters¶

• node_name — Registered node identification string.
• payload — Conduit node containing the simulation data.

melissa::send(const std::string& node_name, double* send_vect, size_t vect_size)¶

Transmits a double-precision (64-bit floating point) simulation array.

This overload wraps the raw array buffer into a temporary zero-copy Conduit node. On Rank 0, arrays from all ranks are automatically concatenated into a single continuous double-precision payload.

Parameters¶

• node_name — Registered node identification string.
• send_vect — Pointer to the raw double-precision array buffer.
• vect_size — Number of double elements contained in the local process slice.

melissa::send(const std::string& node_name, float* send_vect, size_t vect_size)¶

Transmits a single-precision (32-bit floating point) simulation array.

This overload wraps the raw array buffer into a temporary zero-copy Conduit node. On Rank 0, arrays from all ranks are automatically concatenated into a single continuous single-precision payload.

Parameters¶

• node_name — Registered node identification string.
• send_vect — Pointer to the raw single-precision array buffer.
• vect_size — Number of float elements contained in the local process slice.

melissa::finalize()¶

Terminates the Melissa client session.

Releases all ZMQ sockets and internal runtime state. This function must be called before MPI_Finalize().

melissa::Parameters fetch_next_parameters()¶

Fetches the next simulation parameters from the Melissa server.

Only valid in persistent client mode when MELISSA_PERSISTENT_CLIENT_ID is set.

The function blocks until the server responds. Each MPI rank independently reads parameters from the memory-mapped file using the returned simulation ID.

Always is_terminated status before using returned values.

C/Fortran API¶

melissa_init(const char* node_name, MPI_Comm comm)¶

C binding for melissa::init.

melissa_init_f(const char* node_name, MPI_Fint* comm_fortran)¶

Fortran ABI bridge wrapper for melissa::init.

melissa_send_node(const char* node_name, conduit_node* payload)¶

C binding for melissa::send using a Conduit node payload.

melissa_send_double(const char* node_name, double* send_vect, size_t vect_size)¶

C binding for melissa::send using a double-precision array.

melissa_send_float(const char* node_name, float* send_vect, size_t vect_size)¶

C binding for melissa::send using a single-precision array.

melissa_finalize(void)¶

C binding for melissa::finalize.

melissa_parameters_t¶

C layout mapping for data returned by parameter steering iterations which is equivalent to melissa::Parameters.

Members¶

melissa_fetch_next_parameters(void)¶

C binding for melissa::fetch_next_parameters. Returns a pointer to a constant melissa_parameters_t structure containing the next simulation parameters.