setup.h

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#ifndef SETUP_H
#define SETUP_H
 
#include <petscpf.h>
#include <petscdmswarm.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
#include <petsctime.h>
#include <petscsys.h>
#include <petscdmcomposite.h>
#include <petscsystypes.h>
 
// Include additional headers
#include "variables.h"         // Shared type definitions
#include "field_catalog.h"     // Typed identities for persistent Eulerian fields
#include "ParticleSwarm.h"  // Particle swarm functions
#include "walkingsearch.h"  // Particle location functions
#include "grid.h"           // Grid functions
#include "logging.h"        // Logging macros
#include "io.h"             // Data Input and Output functions
#include "interpolation.h"  // Interpolation routines
#include "ParticleMotion.h" // Functions related to motion of particles
#include "Boundaries.h"     //  Functions related to Boundary conditions
 
 
/* Macro to automatically select the correct allocation function */
#define Allocate3DArray(array, nz, ny, nx)  \
  _Generic((array),                          \
    PetscReal ****: Allocate3DArrayScalar,       \
    Cmpnts    ****: Allocate3DArrayVector            \
  )(array, nz, ny, nx)
 
/* Macro for deallocation */
#define Deallocate3DArray(array, nz, ny)  \
  _Generic((array),                        \
    PetscReal ***: Deallocate3DArrayScalar,     \
    Cmpnts    ***: Deallocate3DArrayVector          \
  )(array, nz, ny)
 
 
/**
 * @brief Allocates and populates the master SimulationContext object.
 *
 * This function serves as the single, authoritative entry point for all
 * simulation configuration. It merges the setup logic from both the legacy
 * FSI/IBM solver and the modern particle solver into a unified, robust
 * process.
 *
 * The function follows a strict sequence:
 * 1.  **Allocate Context & Set Defaults:** It first allocates the `SimulationContext`
 *     and populates every field with a sane, hardcoded default value. This
 *     ensures the simulation starts from a known, predictable state.
 * 2.  **Configure Logging System:** It configures the custom logging framework. It
 *     parses the `-func_config_file` option to load a list of function names
 *     allowed to produce log output. This configuration (the file path and the
 *     list of function names) is stored within the `SimulationContext` for
 *     later reference and cleanup.
 * 3.  **Parse All Options:** It performs a comprehensive pass of `PetscOptionsGet...`
 *     calls for every possible command-line flag, overriding the default
 *     values set in step 1.
 * 4.  **Log Summary:** After all options are parsed, it uses the now-active
 *     logging system to print a summary of the key simulation parameters.
 *
 * @param[in]  argc      Argument count passed from `main`.
 * @param[in]  argv      Argument vector passed from `main`.
 * @param[out] p_simCtx  On success, this will point to the newly created and
 *                       fully configured `SimulationContext` pointer. The caller
 *                       is responsible for eventually destroying this object by
 *                       calling `FinalizeSimulation()`.
 *
 * @return PetscErrorCode Returns 0 on success, or a non-zero PETSc error code on failure.
 */
PetscErrorCode CreateSimulationContext(int argc, char **argv, SimCtx **p_simCtx);
 
/**
 * @brief Parse a positive floating-point seconds value from runtime metadata.
 *
 * This helper is used for shell-exported walltime metadata such as
 * `PICURV_JOB_START_EPOCH` and `PICURV_WALLTIME_LIMIT_SECONDS`.
 *
 * @param[in]  text         String to parse.
 * @param[out] seconds_out  Parsed positive seconds value when successful.
 * @return PetscBool `PETSC_TRUE` when parsing succeeds, else `PETSC_FALSE`.
 */
PetscBool RuntimeWalltimeGuardParsePositiveSeconds(const char *text, PetscReal *seconds_out);
 
/**
 * @brief Verifies and prepares the complete I/O environment for a simulation run.
 *
 * This function performs a comprehensive series of checks and setup actions to
 * ensure a valid and clean environment. It is parallel-safe; all filesystem
 * operations and checks are performed by Rank 0, with collective error handling.
 *
 * The function's responsibilities include:
 * 1.  **Checking Mandatory Inputs:** Verifies existence of grid and BCs files.
 * 2.  **Checking Optional Inputs:** Warns if optional config files (whitelist, profile) are missing.
 * 3.  **Validating Run Mode Paths:** Ensures `restart_dir` or post-processing source directories exist when needed.
 * 4.  **Preparing Log Directory:** Creates the log directory and cleans it of previous logs.
 * 5.  **Preparing Output Directories:** Creates the main output directory and its required subdirectories.
 *
 * @param[in] simCtx The fully configured SimulationContext object.
 *
 * @return PetscErrorCode Returns 0 on success, or a non-zero error code if a
 *         mandatory file/directory is missing or a critical operation fails.
 */
PetscErrorCode SetupSimulationEnvironment(SimCtx *simCtx);
 
/**
 * @brief The main orchestrator for setting up all grid-related components.
 *
 * This function is the high-level driver for creating the entire computational
 * domain, including the multigrid hierarchy, PETSc DMDA and Vec objects, and
 * calculating all necessary grid metrics.
 *
 * @param simCtx The fully configured SimulationContext.
 * @return PetscErrorCode
 */
PetscErrorCode SetupGridAndSolvers(SimCtx *simCtx);
 
/**
 @brief Creates and initializes all PETSc Vec objects for all fields.
 *
 * This function iterates through every UserCtx in the multigrid and multi-block
 * hierarchy. For each context, it creates the comprehensive set of global and
 * local PETSc Vecs required by the flow solver (e.g., Ucont, P, Nvert, metrics,
 * turbulence fields, etc.). Each vector is initialized to zero.
 *
 * @param simCtx The master SimCtx, containing the configured UserCtx hierarchy.
 * @return PetscErrorCode
 */
PetscErrorCode CreateAndInitializeAllVectors(SimCtx *simCtx);
 
/**
 * @brief Updates the local vector (including ghost points) from its corresponding global vector.
 *
 * This function resolves the correct global vector, local vector, and DM from the
 * authoritative field catalog and performs the standard PETSc
 * DMGlobalToLocalBegin/End sequence.
 * For registered single-face-family and component-staggered fields, it then
 * repairs the adjacent periodic ghost in each normal direction so central
 * differences see the correct neighboring face. Cell-centered fields and
 * tangential face directions retain PETSc's native periodic wraparound.
 * Includes optional debugging output (max norms before/after).
 *
 * @param user      The UserCtx structure containing the vectors and DMs.
 * @param field_id  Typed identity of the catalogued field to update.
 *
 * @return PetscErrorCode 0 on success, non-zero on failure.
 *
 * @note This function assumes the global vector associated with field_id has already
 *       been populated with the desired data (including any boundary conditions and
 *       periodic duplicate planes). It scatters that current global state into the
 *       local vector; it does not repair stale global periodic duplicate planes.
 * @note Wider QUICK-style normal ghost layers require a separate dedicated
 *       exchange; this function repairs the adjacent layer used by central stencils.
 */
PetscErrorCode UpdateLocalGhosts(UserCtx *user, FieldId field_id);
 
/**
 * @brief (Orchestrator) Sets up all boundary conditions for the simulation.
 *
 * @param simCtx Simulation context controlling the operation.
 * @return PetscErrorCode 0 on success.
 */
PetscErrorCode SetupBoundaryConditions(SimCtx *simCtx);
 
/**
 * @brief Allocates any runtime storage required by solution-convergence logging.
 *
 * This helper is setup-owned because it allocates mode-specific buffers once
 * the finest-level Eulerian vectors already exist. It does not compute or log
 * any metrics; it only prepares storage for later use by
 * `LOG_SOLUTION_CONVERGENCE()`.
 *
 * Allocation depends on the active solution-convergence mode:
 * - steady/transient: no extra storage beyond counters
 * - periodic_deterministic: one phase-aligned `Ucat` / `P` reference slot per
 *   configured period step and per block
 * - statistical_steady: rolling scalar histories sized for two adjacent
 *   windows of `mean_speed` and `mean_ke`
 *
 * The helper also resets the recorded-sample counter so warmup behavior starts
 * from a clean state each time solver setup is rebuilt.
 *
 * @param[in,out] simCtx Master simulation context owning the runtime storage.
 * @return PetscErrorCode 0 on success.
 */
PetscErrorCode InitializeSolutionConvergenceState(SimCtx *simCtx);
 
/**
 * @brief Frees any runtime storage allocated for solution-convergence logging.
 *
 * This helper is the cleanup counterpart to
 * `InitializeSolutionConvergenceState()`. It releases periodic reference
 * buffers and statistical-history arrays, then resets the associated pointers
 * and counters. It is safe to call during teardown even if a given mode never
 * allocated optional storage.
 *
 * @param[in,out] simCtx Master simulation context owning the runtime storage.
 * @return PetscErrorCode 0 on success.
 */
PetscErrorCode DestroySolutionConvergenceState(SimCtx *simCtx);
 
/**
 * @brief Allocates a 3D array of PetscReal values using PetscCalloc.
 *
 * This function dynamically allocates memory for a 3D array of PetscReal values
 * with dimensions nz (layers) x ny (rows) x nx (columns). It uses PetscCalloc1
 * to ensure the memory is zero-initialized.
 *
 * The allocation is done in three steps:
 *  1. Allocate an array of nz pointers (one for each layer).
 *  2. Allocate a contiguous block for nz*ny row pointers and assign each layer’s row pointers.
 *  3. Allocate a contiguous block for all nz*ny*nx PetscReal values.
 *
 * This setup allows the array to be accessed as array[k][j][i], and the memory
 * for the data is contiguous, which improves cache efficiency.
 *
 * @param[out] array Pointer to the 3D array to be allocated.
 * @param[in]  nz    Number of layers (z-direction).
 * @param[in]  ny    Number of rows (y-direction).
 * @param[in]  nx    Number of columns (x-direction).
 *
 * @return PetscErrorCode 0 on success, nonzero on failure.
 */
 PetscErrorCode Allocate3DArrayScalar(PetscReal ****array, PetscInt nz, PetscInt ny, PetscInt nx);
 
/**
 * @brief Deallocates a 3D array of PetscReal values allocated by Allocate3DArrayScalar.
 *
 * This function frees the memory allocated for a 3D array of PetscReal values.
 * It assumes the memory was allocated using Allocate3DArrayScalar, which allocated
 * three separate memory blocks: one for the contiguous data, one for the row pointers,
 * and one for the layer pointers.
 *
 * @param[in] array Pointer to the 3D array to be deallocated.
 * @param[in] nz    Number of layers (z-direction).
 * @param[in] ny    Number of rows (y-direction).
 *
 * @return PetscErrorCode 0 on success, nonzero on failure.
 */
PetscErrorCode Deallocate3DArrayScalar(PetscReal ***array, PetscInt nz, PetscInt ny);
 
/**
 * @brief Allocates a contiguous 3D array of `Cmpnts` values.
 *
 * The memory layout mirrors `Allocate3DArrayScalar`: layer pointers, row pointers,
 * and contiguous payload are allocated such that indexing as `array[k][j][i]` is valid
 * while keeping payload data contiguous.
 *
 * @param[out] array Pointer to the 3D vector array to allocate.
 * @param[in]  nz    Number of layers in the z-direction.
 * @param[in]  ny    Number of rows in the y-direction.
 * @param[in]  nx    Number of columns in the x-direction.
 * @return PetscErrorCode 0 on success, nonzero on failure.
 */
 PetscErrorCode Allocate3DArrayVector(Cmpnts ****array, PetscInt nz, PetscInt ny, PetscInt nx);
 
/**
 * @brief Deallocates a 3D array of Cmpnts structures allocated by Allocate3DArrayVector.
 *
 * This function frees the memory allocated for a 3D array of Cmpnts structures.
 * It assumes the memory was allocated using Allocate3DArrayVector, which created three
 * separate memory blocks: one for the contiguous vector data, one for the row pointers,
 * and one for the layer pointers.
 *
 * @param[in] array Pointer to the 3D array to be deallocated.
 * @param[in] nz    Number of layers in the z-direction.
 * @param[in] ny    Number of rows in the y-direction.
 *
 * @return PetscErrorCode 0 on success, nonzero on failure.
 */
PetscErrorCode Deallocate3DArrayVector(Cmpnts ***array, PetscInt nz, PetscInt ny);
 
/**
 * @brief Determines the global starting index and number of CELLS owned by the
 *        current processor in a specified dimension. Ownership is defined by the
 *        rank owning the cell's origin node (min i,j,k corner).
 *
 * @param[in]  info_nodes     Pointer to the DMDALocalInfo struct obtained from the NODE-based DMDA
 *                            (e.g., user->da or user->fda, assuming they have consistent nodal partitioning
 *                            for defining cell origins).
 * @param[in]  dim            The dimension to compute the range for (0 for x/i, 1 for y/j, 2 for z/k).
 * @param[out] xs_cell_global_out Pointer to store the starting global cell index owned by this process.
 * @param[out] xm_cell_local_out  Pointer to store the number of owned cells in this dimension.
 *
 * @return PetscErrorCode 0 on success.
 */
PetscErrorCode GetOwnedCellRange(const DMDALocalInfo *info_nodes,
                                 PetscInt dim,
                                 PetscInt *xs_cell_global_out,
                                 PetscInt *xm_cell_local_out);
 
/**
 * @brief Computes and stores the Cartesian neighbor ranks for the DMDA decomposition.
 *
 * This function retrieves the neighbor information from the primary DMDA (user->da)
 * and stores the face neighbors (xm, xp, ym, yp, zm, zp) in the user->neighbors structure.
 * It assumes a standard PETSc ordering for the neighbors array returned by DMDAGetNeighbors.
 * Logs warnings if the assumed indices seem incorrect (e.g., center rank mismatch).
 *
 * @param[in,out] user Pointer to the UserCtx structure where neighbor info will be stored.
 *
 * @return PetscErrorCode 0 on success, non-zero on failure.
 */
PetscErrorCode ComputeAndStoreNeighborRanks(UserCtx *user);
 
/**
 * @brief Sets the processor layout for a given DMDA based on PETSc options.
 *
 * Reads the desired number of processors in x, y, and z directions using
 * PETSc options (e.g., -dm_processors_x, -dm_processors_y, -dm_processors_z).
 * If an option is not provided for a direction, PETSC_DECIDE is used for that direction.
 * Applies the layout using DMDASetNumProcs.
 *
 * Also stores the retrieved/decided values in user->procs_x/y/z if user context is provided.
 *
 * @param dm   The DMDA object to configure the layout for.
 * @param user Pointer to the UserCtx structure (optional, used to store layout values).
 *
 * @return PetscErrorCode 0 on success, non-zero on failure.
 */
PetscErrorCode SetDMDAProcLayout(DM dm, UserCtx *user);
 
/**
 * @brief Sets up the full rank communication infrastructure, including neighbor ranks and bounding box exchange.
 *
 * This function orchestrates the following steps:
 * 1. Compute and store the neighbor ranks in the user context.
 * 2. Gather all local bounding boxes to rank 0.
 * 3. Broadcast the complete bounding box list to all ranks.
 *
 * The final result is that each rank has access to its immediate neighbors and the bounding box information of all ranks.
 *
 * @param[in,out] simCtx Pointer to initialized simulation context that owns all block UserCtx objects.
 *
 * @return PetscErrorCode Returns 0 on success or non-zero PETSc error code.
 */
PetscErrorCode SetupDomainRankInfo(SimCtx *simCtx);
 
/**
 * @brief Reconstructs Cartesian velocity (Ucat) at cell centers from contravariant
 *        velocity (Ucont) defined on cell faces.
 *
 * This function performs the transformation from a contravariant velocity representation
 * (which is natural on a curvilinear grid) to a Cartesian (x,y,z) representation.
 * For each interior computational cell owned by the rank, it performs the following:
 *
 * 1.  It averages the contravariant velocity components (U¹, U², U³) from the
 *     surrounding faces to get an estimate of the contravariant velocity at the cell center.
 * 2.  It averages the metric vectors (Csi, Eta, Zet) from the surrounding faces
 *     to get an estimate of the metric tensor at the cell center. This tensor forms
 *     the transformation matrix.
 * 3.  It solves the linear system `[MetricTensor] * [ucat] = [ucont]` for the
 *     Cartesian velocity vector `ucat = (u,v,w)` using Cramer's rule.
 * 4.  The computed Cartesian velocity is stored only at independent owned cells in
 *     the global `user->Ucat` vector.
 *
 * The function operates on local, ghosted versions of the input vectors (`user->lUcont`,
 * `user->lCsi`, etc.) to ensure stencils are valid across processor boundaries.
 *
 * @param[in,out] user      Pointer to the UserCtx structure. The function reads from
 *                          `user->lUcont`, `user->lCsi`, `user->lEta`, `user->lZet`, `user->lNvert`
 *                          and writes to the global `user->Ucat` vector.
 *
 * @return PetscErrorCode 0 on success.
 *
 * @note
 *  - This function should be called AFTER `user->lUcont` and all local metric vectors
 *    (`user->lCsi`, etc.) have been populated with up-to-date ghost values via `UpdateLocalGhosts`.
 *  - It only computes `Ucat` for interior cells (not on physical boundaries) and for
 *    cells not marked as solid/blanked by `user->lNvert`.
 *  - The function performs no communication, does not synchronize periodic duplicate
 *    planes, and does not refresh `user->lUcat`.
 *  - Before stencil consumption, the caller must synchronize periodic cell values with
 *    `SynchronizePeriodicCellFields(user, 1, {FIELD_ID_UCAT})` and then call
 *    `UpdateLocalGhosts(user, FIELD_ID_UCAT)`. The latter remains necessary for the fully
 *    nonperiodic case because periodic synchronization is then a no-op.
 */
PetscErrorCode Contra2Cart(UserCtx *user);
 
/**
 * @brief Convert the ghosted Cartesian velocity field to contravariant face fluxes.
 * @ingroup InitialConditions
 *
 * Interpolates `user->lUcat` to each logical face and dots it with the
 * corresponding face-area metric vector. Writes independent entries of
 * `user->Ucont`. Periodic and physical endpoint values in `user->lUcat` must be
 * finalized and its MPI ghosts current before entry. The resulting `Ucont` is not
 * synchronized; callers must use the staggered-field workflow before stencil use.
 *
 * @param[in,out] user  UserCtx for the block; Ucont is written in place.
 * @return PetscErrorCode 0 on success.
 */
PetscErrorCode Cart2Contra(UserCtx *user);
 
/**
 * @brief Populate contravariant fluxes from one uniform Cartesian velocity.
 *
 * @param[in,out] user UserCtx for the block; Ucont is written in place.
 * @param[in] u Physical x-velocity component.
 * @param[in] v Physical y-velocity component.
 * @param[in] w Physical z-velocity component.
 * @return PetscErrorCode 0 on success.
 */
PetscErrorCode UniformCart2Contra(UserCtx *user, PetscReal u, PetscReal v, PetscReal w);
 
 
/**
 * @brief Creates and distributes a map of the domain's cell decomposition to all ranks.
 * @ingroup DomainInfo
 *
 * This function is a critical part of the simulation setup. It determines the global
 * cell ownership for each MPI rank and makes this information available to all
 * other ranks. This "decomposition map" is essential for the robust "Walk and Handoff"
 * particle migration strategy, allowing any rank to quickly identify the owner of a
 * target cell.
 *
 * The process involves:
 * 1. Each rank gets its own node ownership information from the DMDA.
 * 2. It converts this node information into cell ownership ranges using the
 *    `GetOwnedCellRange` helper function.
 * 3. It participates in an `MPI_Allgather` collective operation to build a complete
 *    array (`user->RankCellInfoMap`) containing the ownership information for every rank.
 *
 * This function should be called once during initialization after the primary DMDA
 * (user->da) has been set up.
 *
 * @param[in,out] user Pointer to the UserCtx structure. The function will allocate and
 *                     populate `user->RankCellInfoMap` and set `user->num_ranks`.
 *
 * @return PetscErrorCode 0 on success, or a non-zero PETSc error code on failure.
 *         Errors can occur if input pointers are NULL or if MPI communication fails.
 */
PetscErrorCode SetupDomainCellDecompositionMap(UserCtx *user);
 
/**
 * @brief Performs a binary search for a key in a sorted array of PetscInt64.
 *
 * This is a standard binary search algorithm implemented as a PETSc-style helper function.
 * It efficiently determines if a given `key` exists within a `sorted` array.
 *
 * @param[in]  n      The number of elements in the array.
 * @param[in]  arr    A pointer to the sorted array of PetscInt64 values to be searched.
 * @param[in]  key    The PetscInt64 value to search for.
 * @param[out] found  A pointer to a PetscBool that will be set to PETSC_TRUE if the key
 *                    is found, and PETSC_FALSE otherwise.
 *
 * @return PetscErrorCode 0 on success, or a non-zero PETSc error code on failure.
 *
 * @note The input array `arr` **must** be sorted in ascending order for the algorithm
 *       to work correctly.
 */
PetscErrorCode BinarySearchInt64(PetscInt n, const PetscInt64 arr[], PetscInt64 key, PetscBool *found);
 
 
/**
 * @brief Computes the discrete divergence of the contravariant velocity field.
 *
 * This diagnostic/kernel routine evaluates continuity residuals on the local block
 * and writes the resulting divergence field into the configured output vector(s).
 *
 * @param[in,out] user Block-level context containing velocity and metric fields.
 * @return PetscErrorCode 0 on success.
 */
PetscErrorCode ComputeDivergence(UserCtx *user);
 
/**
 * @brief Initializes random number generators for assigning particle properties.
 *
 * This function creates and configures separate PETSc random number generators for the x, y, and z coordinates.
 *
 * @param[in,out] user    Pointer to the UserCtx structure containing simulation context.
 * @param[out]    randx   Pointer to store the RNG for the x-coordinate.
 * @param[out]    randy   Pointer to store the RNG for the y-coordinate.
 * @param[out]    randz   Pointer to store the RNG for the z-coordinate.
 *
 * @return PetscErrorCode Returns 0 on success, non-zero on failure.
 */
PetscErrorCode InitializeRandomGenerators(UserCtx *user, PetscRandom *randx, PetscRandom *randy, PetscRandom *randz);
 
/**
 * @brief Initializes random number generators for logical space operations [0.0, 1.0).
 *
 * This function creates and configures three separate PETSc random number generators,
 * one for each logical dimension (i, j, k or xi, eta, zeta equivalent).
 * Each RNG is configured to produce uniformly distributed real numbers in the interval [0.0, 1.0).
 * These are typically used for selecting owned cells or generating intra-cell logical coordinates.
 *
 * @param[out]   rand_logic_i Pointer to store the RNG for the i-logical dimension.
 * @param[out]   rand_logic_j Pointer to store the RNG for the j-logical dimension.
 * @param[out]   rand_logic_k Pointer to store the RNG for the k-logical dimension.
 *
 * @return PetscErrorCode Returns 0 on success, non-zero on failure.
 */
PetscErrorCode InitializeLogicalSpaceRNGs(PetscRandom *rand_logic_i, PetscRandom *rand_logic_j, PetscRandom *rand_logic_k);
 
/**
 * @brief Initializes a single master RNG for time-stepping physics (Brownian motion).
 *        Configures it for Uniform [0, 1) which is required for Box-Muller transformation.
 *
 * @param[in,out] simCtx  Pointer to the Simulation Context.
 * @return PetscErrorCode
 */
PetscErrorCode InitializeBrownianRNG(SimCtx *simCtx);
 
/**
 * @brief Transforms scalar derivatives from computational space to physical space
 *
 * using the chain rule.
 * Formula: dPhi/dx = J * ( dPhi/dCsi * dCsi/dx + dPhi/dEta * dEta/dx + ... )
 *
 * @param jacobian Local mapping Jacobian determinant.
 * @param csi_metrics Physical gradient of the xi coordinate.
 * @param eta_metrics Physical gradient of the eta coordinate.
 * @param zet_metrics Physical gradient of the zeta coordinate.
 * @param dPhi_dcsi Scalar derivative in the xi direction.
 * @param dPhi_deta Scalar derivative in the eta direction.
 * @param dPhi_dzet Scalar derivative in the zeta direction.
 * @param[out] gradPhi Physical Cartesian scalar gradient.
 */
 void TransformScalarDerivativesToPhysical(PetscReal jacobian, 
                                                 Cmpnts csi_metrics, 
                                                 Cmpnts eta_metrics, 
                                                 Cmpnts zet_metrics,
                                                 PetscReal dPhi_dcsi, 
                                                 PetscReal dPhi_deta, 
                                                 PetscReal dPhi_dzet,
                                                 Cmpnts *gradPhi);
 
/**
 * @brief Computes the gradient of a cell-centered SCALAR field at a specific grid point.
 *
 * @param user Block metric context.
 * @param i Cell index in the xi direction.
 * @param j Cell index in the eta direction.
 * @param k Cell index in the zeta direction.
 * @param field_data Ghosted scalar values indexed as [k][j][i].
 * @param[out] grad Physical Cartesian gradient at the requested cell.
 * @return PetscErrorCode 0 on success.
 */
PetscErrorCode ComputeScalarFieldDerivatives(UserCtx *user, PetscInt i, PetscInt j, PetscInt k, 
                                             PetscReal ***field_data, Cmpnts *grad);
 
/**
 * @brief Computes the derivatives of a cell-centered vector field at a specific grid point.
 *
 * This function orchestrates the calculation of spatial derivatives. It first computes
 * the derivatives in computational space (d/dcsi, d/deta, d/dzet) using a central
 * difference scheme and then transforms them into physical space (d/dx, d/dy, d/dz).
 *
 * @param user Block metric context.
 * @param i Cell index in the xi direction.
 * @param j Cell index in the eta direction.
 * @param k Cell index in the zeta direction.
 * @param field_data Ghosted Cartesian vector values indexed as [k][j][i].
 * @param[out] dudx Gradient of the x velocity component.
 * @param[out] dvdx Gradient of the y velocity component.
 * @param[out] dwdx Gradient of the z velocity component.
 * @return PetscErrorCode 0 on success.
 */
PetscErrorCode ComputeVectorFieldDerivatives(UserCtx *user, PetscInt i, PetscInt j, PetscInt k, Cmpnts ***field_data,
                                             Cmpnts *dudx, Cmpnts *dvdx, Cmpnts *dwdx);
 
/**
 * @brief Destroys all PETSc Vec objects within a single UserCtx structure.
 *
 * This helper function systematically destroys the Vec objects stored in a UserCtx.
 * The vectors are organized into functional groups for clarity:
 *   - Primary flow fields (Ucont, Ucat, P, Nvert)
 *   - Solver work vectors (Phi)
 *   - Time-stepping vectors (Ucont_o, Ucont_rm1, etc.)
 *   - Grid metrics (cell-centered, face-centered, coordinates)
 *   - Turbulence vectors (Nu_t, CS, lFriction_Velocity)
 *   - Particle vectors (ParticleCount, Psi)
 *   - Boundary condition vectors (Ubcs, Uch)
 *   - Post-processing vectors (P_nodal, Qcrit)
 *   - And more...
 *
 * All destroys are protected with NULL checks to handle conditional allocations safely.
 *
 * @param[in,out] user Pointer to the UserCtx containing the vectors to destroy.
 *
 * @return PetscErrorCode 0 on success.
 */
PetscErrorCode DestroyUserVectors(UserCtx *user);
 
/**
 * @brief Destroys all resources allocated within a single UserCtx structure.
 *
 * This function cleans up all memory and PETSc objects associated with a single
 * UserCtx (grid level). It calls the helper functions and destroys remaining objects
 * in the proper dependency order:
 *   1. Boundary conditions (handlers and their data)
 *   2. All PETSc vectors (via DestroyUserVectors)
 *   3. Matrix and solver objects (A, C, MR, MP, ksp, nullsp)
 *   4. Application ordering (AO)
 *   5. Distributed mesh objects (DMs) - most derived first
 *   6. Raw PetscMalloc'd arrays (RankCellInfoMap, KSKE)
 *
 * This function should be called for each UserCtx in the multigrid hierarchy.
 *
 * @param[in,out] user Pointer to the UserCtx to be destroyed.
 *
 * @return PetscErrorCode 0 on success.
 */
PetscErrorCode DestroyUserContext(UserCtx *user);
 
/**
 * @brief Main cleanup function for the entire simulation context.
 *
 * This function is responsible for destroying ALL memory and PETSc objects allocated
 * during the simulation, including:
 *   - All UserCtx structures in the multigrid hierarchy (via DestroyUserContext)
 *   - The multigrid management structures (UserMG, MGCtx array)
 *   - All SimCtx-level objects (logviewer, dm_swarm, bboxlist, string arrays, etc.)
 *   - The SimCtx allocation itself.
 *
 * This function should be called ONCE at the end of the simulation, after all
 * computation is complete, but BEFORE PetscFinalize().
 *
 * Call order in main:
 *   1. [Simulation runs]
 *   2. ProfilingFinalize(simCtx);
 *   3. FinalizeSimulation(simCtx);  <- This function
 *   4. PetscFinalize();
 *
 * @param[in,out] simCtx Pointer to the master SimulationContext to be destroyed.
 *                      The pointer is invalid after this call returns.
 *
 * @return PetscErrorCode 0 on success.
 */
PetscErrorCode FinalizeSimulation(SimCtx *simCtx);
 
 
 #endif // SETUP_H