New Features and Enhancements
We added a new SUNNonlinearSolver implementation, SUNNonlinearSolver_Auto, which uses an algorithm described in https://doi.org/10.1007/BF01933714 to switch between a modified Newton iteration and fixed-point iteration based on an estimate of stiffness. This solver may be useful to pair with the BDF method in CVODE/CVODES, or with DIRK methods in ARKODE, for users who are unsure about the stiffness of their problem. See the module documentation for more information. We also extended the SUNNonlinearSolver API with callback setters SUNNonlinSolSetNormFn, SUNNonlinSolSetGetUpdateNormFn, and SUNNonlinSolSetGetConvRateFn.
Added the ARKODE_SSP_ERK_3_1_2, ARKODE_SSP_ERK_4_1_2, ARKODE_SSP_ERK_4_2_3, ARKODE_SSP_ERK_10_3_4, ARKODE_SSP_LSPUM_ERK_3_1_2, and ARKODE_ASCHER_ERK_3_1_2 embedded explicit Runge-Kutta Butcher tables.
Added the ARKODE_SSP_DIRK_3_1_2, ARKODE_SSP_LSPUM_SDIRK_3_1_2, ARKODE_ESDIRK_4_2_3, and ARKODE_ASCHER_SDIRK_3_1_2 embedded diagonally implicit Runge-Kutta Butcher tables.
Of these, embedded additive Runge-Kutta methods may be formed using ARKODE_SSP_ERK_3_1_2+ARKODE_SSP_DIRK_3_1_2, ARKODE_SSP_ERK_4_2_3+ARKODE_ESDIRK_4_2_3, ARKODE_SSP_LSPUM_ERK_3_1_2+ARKODE_SSP_LSPUM_SDIRK_3_1_2, and ARKODE_ASCHER_ERK_3_1_2+ARKODE_ASCHER_SDIRK_3_1_2.
Added the ARKODE_IMEX_MRI_GARK_ASCHER_ARK2 and ARKODE_IMEX_MRI_GARK_ARK2 embedded implicit-explicit MRI-GARK coupling tables.
When info or debug logging is enabled, i.e., SUNDIALS_LOGGING_LEVEL is at least 3, it will now print to stdout by default. Previously, the default was to produce no output, and this behavior can be restored by setting the environment variables SUNLOGGER_INFO_FILENAME and SUNLOGGER_DEBUG_FILENAME to an empty string.
Improved the performance of logging when enabled but no file pointer was set.
Added the function SUNLogger_SetQueueAndFlushMsgFns to allow for user-defined functions to queue and flush log messages.
Updated examples/cvode/petsc/cv_petsc_ex7.c to support PETSc 3.25.0.
Bug Fixes
Fixed a bug where an unrecognized error return flag from a user-provided SUNLinearSolver module would register as a successful linear solve.
Fixed a bug that caused SUNDomEigEstimator_Initialize to overwrite the user-provided initial guess from SUNDomEigEstimator_SetInitialGuess. These routines are now order-independent.
Fixed memory leaks in CVODES, IDAS, and KINSOL in the unlikely event of a failed malloc.
Fixed a bug in ERKStep where calling ARKodeResize before ARKodeEvolve or ARKodeInit would result in a segmentation fault.
Fixed a bug where the number of required stages for STS methods in the LSRKStep module was incorrectly computed using the spectral radius instead of the real part of the Jacobian eigenvalues.
Fixed a bug where the negative real extent of the stability region for the RKC method was not properly computed, which could result in an underestimation of the number of stages required for stability.
Fixed a bug where STS methods were limited to one fewer than the maximum allowed number of stages. STS can now use the full maximum number of stages.
Fixed a bug in reporting the maximum number of stages in ARKodeGetStageIndex when running SSP methods in LSRKStep.
Fixed a bug where IDAS would incorrectly compute the quadrature predictor when IDACalcIC was used. In some cases, this lead to an inconsistent solution in the forward solve compared to the forward recomputation from a checkpoint, ultimately causing a segfault.
Fixed a bug in the sundials4py wrappers for user-provided SUNStepper evolve and one_step functions.
Fixed a bug in sundials4py where the CVodeGetRootInfo, ARKodeGetRootInfo, and IDAGetRootInfo functions did not correctly return the rootsfound array. This addresses Issue #937.
Removed duplicate logging output that would cause the Python logging tools to fail with a repeated key error.
Fixed a CMake issue that prevented finding third-party libraries installed in default search locations e.g., paths included in CMAKE_INSTALL_PREFIX (Issue #935).
Fixed a CMake issue that prevented automatically finding PETSc dependencies.
Fixed empty elseif() cases in the CMake files for the Fortran interfaces to the ManyVector and MPIPlusX vectors which could results in a missing include path when compiling if an MPI compiler wrapper is not found.
Fixed a CMake bug where Fortran modules were not created for LSRKStep, ForcingStep, and SplittingStep.
Corrected the version number used in version added, changed, and deprecated notes in the documentation to always use the SUNDIALS version number with the package version number as a parenthetical note when it differs from the SUNDIALS version number.