hipBLASLt environment variables

This section describes the important hipBLASLt environment variables, which are grouped by functionality.

Logging and debugging

The logging and debugging environment variables for hipBLASLt are collected in the following table. For more information, see Use logging and heuristics.

Environment variable	Value
HIPBLASLT_LOG_LEVEL Controls the verbosity level of hipBLASLt logging output.	0: Off (logging disabled, default) 1: Error (only errors are logged) 2: Trace (API calls with kernel launches log parameters) 3: Hints (performance improvement suggestions) 4: Info (general library execution information) 5: API trace (detailed API call parameters)
HIPBLASLT_LOG_MASK Controls logging output using bit mask flags (can be combined).	0: Off 1: Error 2: Trace 4: Hints 8: Info 16: API trace 32: Bench 64: Profile 128: Extended profile
HIPBLASLT_LOG_FILE Specifies path to logging file. Can contain %i for process ID replacement.	Path to log file (for example, logfile_%i.log) If not defined: log messages printed to stdout
HIPBLASLT_ENABLE_MARKER Enables marker trace for ROCProfiler profiling.	0 or unset: Disable marker trace 1: Enable marker trace

Offline tuning

The offline tuning environment variables for hipBLASLt are collected in the following table. For more information, see Use hipBLASLt offline tuning.

Environment variable	Value
HIPBLASLT_TUNING_FILE Specifies file to store tuning results with best solution indices for GEMM problems.	Path to tuning file (for example, tuning.txt) File stores optimal kernel indices for reuse
HIPBLASLT_TUNING_OVERRIDE_FILE Specifies file to load tuning results and override default kernel selection.	Path to tuning file (for example, tuning.txt) Loads previously saved optimal kernel choices
HIPBLASLT_TUNING_USER_MAX_WORKSPACE Sets maximum workspace size constraint during tuning stage.	Integer value in bytes (default: 128 * 1024 * 1024) Limits workspace size for solution selection

Origami with Stream-K configuration

The Origami with Stream-K configuration environment variables for hipBLASLt are collected in the following table. These variables apply to all GEMMs in an application. For more information, see Use Stream-K with hipBLASLt.

The TENSILE_PERSISTENT_* launch controls apply to persistent kernels, including Stream-K and persistent DataParallel. The legacy aliases listed below remain supported. When both names are set, the preferred name takes precedence, even if its value is invalid; it does not fall back to the legacy value.

Environment variable	Value
TENSILE_SOLUTION_SELECTION_METHOD Controls hipBLASLt kernel selection strategy for GEMM operations.	0: Default (standard tuned libraries, no Stream-K) 2: Origami with Stream-K (enables Origami solution selection for consistent performance) This variable has no effect on the AMD Instinct™ MI350 series. Stream-K is always used.
TENSILE_PERSISTENT_DYNAMIC_GRID Legacy alias: TENSILE_STREAMK_DYNAMIC_GRID. Controls persistent grid size selection behavior.	0: Disable dynamic grid (use all available compute units) 1: Only reduce compute units for small problems to the number of output tiles when num_tiles < CU count 2: Also reduce compute units for large sizes to improve the data-parallel portion and reduce power 3: Analytically predict the best grid size by weighing the cost of the fix-up step and the cost of processing MACs 4: The Stream-K algorithm behaves like data parallel (Launch WGs = number of CUs) 5: The Stream-K algorithm uses the Origami select_best_grid_size function 6: Default (automatically pick the optimal workgroup count)
TENSILE_GRIDBASED_KDTREE Force-enables the k-d tree index on grid-based solution-selection tables, which are otherwise scanned linearly. Enable-only: it can switch the index on for tables that do not ask for it, but it can never switch it off. A table that declares UseKdTree: true in its library-logic file already uses the index with this variable unset, and no value of this variable changes that. Affects which kernel is selected, not the result it computes.	Unset or 0: Each grid-based table uses the UseKdTree value declared in its library-logic file. Tables that do not declare it are scanned linearly. Non-zero: Enable the index for every grid-based table, in addition to those already declaring UseKdTree: true. To disable the index for a table that declares UseKdTree: true, remove the key (or set it to false) in that table’s library-logic file and rebuild the device library. This cannot be done at runtime.
TENSILE_PERSISTENT_FIXED_GRID Legacy alias: TENSILE_STREAMK_FIXED_GRID. Overrides the default persistent grid size, subject to the kernel’s launch limits.	Positive integer specifying the number of workgroups Default: 0 (no override) Example: 64 (limits GEMM kernels to 64 workgroups)
TENSILE_PERSISTENT_MAX_CUS Legacy alias: TENSILE_STREAMK_MAX_CUS. Sets the compute-unit budget used for persistent grid sizing.	Positive integer specifying the compute-unit budget Example: 32 Default: 0 (all available compute units)
TENSILE_PERSISTENT_GRID_MULTIPLIER Legacy alias: TENSILE_STREAMK_GRID_MULTIPLIER. Multiplies the compute-unit count to size the persistent grid when dynamic grid selection and the CU cap are disabled and no fixed grid is set. The resulting grid remains subject to the kernel’s launch limits.	Integer greater than 1 to enable multiplication Default: 1
TENSILE_PERSISTENT_DYNAMIC_WGM Legacy alias: TENSILE_STREAMK_DYNAMIC_WGM. Retained for compatibility; currently has no effect on workgroup mapping.	Default: 0
TENSILE_PERSISTENT_HYBRID_FORCE_MODE Legacy alias: TENSILE_STREAMK5_FORCE_MODE. Debug override for the mode of an already selected Hybrid kernel; does not select the kernel family.	-1: Respect the normal assignment policy (default) 0: Force static assignment 1: Force dynamic work-queue assignment Malformed or out-of-range values are ignored.

Type overrides

Overrides for specific types.

Environment variable	Value
HIPBLASLT_OVERRIDE_COMPUTE_TYPE_XF32 Overrides the compute type used for GEMMs which specify a compute type of XF32.	-1: Off (Default) 0: F32 1: XF32(eg TF32) 2: F32_BF16