env_variables.md

Environment variables used by hipSYCL

• HIPSYCL_DEBUG_LEVEL: if set, overrides the output verbosity. 0: none, 1: error, 2: warning, 3: info, 4: verbose, default is the value of HIPSYCL_DEBUG_LEVEL macro.
• HIPSYCL_VISIBILITY_MASK: can be used to activate only a subset of backends. Syntax: backend;backend2;... Possible values are omp, cuda, hip and ze (as level zero is the backend and spirv in HIPSYCL_TARGETS just the target format). omp will always be active as a CPU backend is required. Device level visibility has to be set via vendor specific variables for now, including {CUDA,HIP}_VISIBLE_DEVICES and ZE_AFFINITY_MASK.
• HIPSYCL_RT_DAG_REQ_OPTIMIZATION_DEPTH: maximum depth when descending the DAG requirement tree to look for DAG optimization opportunities, such as eliding unnecessary dependencies.
• HIPSYCL_RT_MQE_LANE_STATISTICS_MAX_SIZE: For the multi_queue_executor, the maximum size of entries in the lane statistics, i.e. the maximum number of submissions to retain statistical information about. This information is used to estimate execution lane utilization.
• HIPSYCL_RT_MQE_LANE_STATISTICS_DECAY_TIME_SEC: The time in seconds (floating point value) after which to forget information about old submissions.
• HIPSYCL_RT_SCHEDULER: Set scheduler type. Allowed values:
  • direct is a low-latency direct-submission scheduler.
  • unbound is the default scheduler and supports automatic work distribution across multiple devices. If the HIPSYCL_EXT_MULTI_DEVICE_QUEUE extension is used, the scheduler must be unbound.
• HIPSYCL_DEFAULT_SELECTOR_BEHAVIOR: Set behavior of default selector. Allowed values:
  • strict (default): Strictly behave as defined by the SYCL specification
  • multigpu: Makes default selector behave like a multigpu selector from the HIPSYCL_EXT_MULTI_DEVICE_QUEUE extension
  • system: Makes default selector behave like a system selector from the HIPSYCL_EXT_MULTI_DEVICE_QUEUE extension