CHANGELOG.md

# Changelog for TransferBench

Documentation for TransferBench is available at
[https://rocm.docs.amd.com/projects/TransferBench](https://rocm.docs.amd.com/projects/TransferBench).

## v1.65.00
### Added
- Added warp-level dispatch support via GFX_SE_TYPE environment variable
  - GFX_SE_TYPE=0 (default): Threadblock-level dispatch, each subexecutor is a threadblock
  - GFX_SE_TYPE=1: Warp-level dispatch, each subexecutor is a single warp
- Added compile-time template specialization for numSrcs/numDsts in GpuReduceKernel
  - Instantiates optimized kernels for common Transfer types:
    - Copy (1 src → 1 dst): Optimized single-source data copy
    - Read-only (1 src → 0 dst): Optimized memory read validation
    - Write-only (0 src → 1 dst): Optimized memory write/initialization
  - Compiler eliminates dead code loops for these specialized cases, improving performance by up to 7% for all-to-all workloads on MI3xx machines

## v1.64.00
### Added
- Added BLOCKSIZES to a2asweep preset to allow also sweeping over threadblock sizes
- Added FILL_COMPRESS to allow more control over input data pattern
  - FILL_COMPRESS takes in a comma-separated list of integer percentages (that must add up to 100)
    that sets the percentages of 64B lines to be filled by random/1B0/2B0/4B0/32B0 data patterns
    - Bins:
      - 0 - random
      - 1 - 1B0    upper 1 byte of each aligned 2 bytes is 0
      - 2 - 2B0    upper 2 bytes of each aligned 4 bytes is 0
      - 3 - 4B0    upper 4 bytes of each aligned 8 bytes is 0
      - 4 - 32B0   upper 32 bytes of each aligned 64-byte line are 0
  - FILL_PATTERN will be ignored if FILL_COMPRESS is specified
- Additional details about data patterns generated will be printed if the debug env var DUMP_LINES is
  set to a non-zero value, which also corresponds to how many 64 byte lines will be printed
### Modified
- Increased GFX_BLOCKSIZE limit from 512 to 1024 (still requires multiple of 64)

### Fixed
- Fixed bug when using BYTE_OFFSET

## v1.63.00
### Added
- Added `gfx950`, `gfx1150`, and `gfx1151` to default GPU targets list in CMake builds

### Modified
- Removing self-GPU check for DMA engine copies
- Switched to amdclang++ as primary compiler
- healthcheck preset adds HBM testing and support for more MI3XX variants

### Fixed
- Fixed issue when using "P" memory type and specific DMA subengines
- Fixed issue with subiteration timing reports

## v1.62.00
### Added
- Adding GFX_TEMPORAL to allow for use for use of non-temporal loads/stores
  - (0 = none [default], 1 = load, 2 = store, 3 = both)
- Addding "P" memory type which maps to CPU memory but is indexed by closest GPU
  - For example, P4 refers to CPU memory on NUMA node closest to GPU 4
### Modified
- Adding some additional summary details to a2a preset

## v1.61.00
### Added
- Added a2a_n preset which conducts alltoall GPU-to-GPU tranfers over nearest NIC executors
- Re-implemented GFX_BLOCK_ORDER which allows for control over how threadblocks of multiple transfers are ordered
  - 0 = sequential, 1 = interleaved, 2 = random
- Added a2asweep preset which tries various CU/unroll options for GFX-executed all-to-all
- Rewrite main GID index detection logic
- Show the GID index and description in the topology table. It is helpful for debugging purposes
- Added GFX_WORD_SIZE to allow for different packed float sizes to use for GFX kernel.  Must be either 4 (default), 2 or 1


### Fixed
- Avoid build errors for CMake and Makefile if infiniband/verbs.h header is not present and disable NIC executor in such case
- Have a priority list of which GID entry to go for instead of hardcoding choices based on underdocumented user input (such as RoCE version and IP address family)
- Use link-local when it is the only choice (i.e. when routing information is not available beyond local link)

## v1.60.00
### Modified
- Reverted GFX_SINGLE_TEAM default back to 1

### Fixed
- Fixed bug where peer memory access was not enabled for DMA transfers, which would break specific DMA engine transfers

## v1.59.01
### Added
- The a2a preset A2A_MODE variable has been enhanced to allow for customizing the number of srcs/dsts to use
  This is specified by setting A2A_MODE to numSrcs:numDsts.  Extra destinations past 1 will be "local" writes (i.e. if one sets A2A_MODE=1:3, then transfers will follow this pattern: Fx Gx FyFxFx)
  to simulate similar conditions normally used during collective algorithms such as ring-based AllReduce

## v1.59.00
### Added
- Adding in support for NIC executor, which allows for RDMA copies on NICs that support IBVerbs
  By default, NIC executor will be enabled if IBVerbs is found in the dynamic linker cache
- NIC executor can be indexed in two methods
  - "I"   Ix.y will use NIC x as the source and NIC y as the destination.
          E.g. (G0 I0.5 G4)
  - "N"   Nx.y will use NIC closest to GPU x as source, and NIC closest to GPU y as destination
          E.g. (G0 N0.4 N4)
- The closest NIC can be overridden by the environment variable CLOSEST_NIC, which should be a comma-separated
  list of NIC indices to use for the corresponding GPU
- This feature can be explicitly disabled at compile time by specifying DISABLE_NIC_EXEC=1

### Modified
- Changing default data size to 256M from 64M
- Adding NUM_QUEUE_PAIRS which enables NIC traffic in A2A.  Each GPU will talk to the next GPU via the closest NIC
- Sweep preset now saves last sweep run configuration to /tmp/lastSweep.cfg and can be changed via SWEEP_FILE

### Fixed
- Fixed bug with reporting when using subiterations
- Fixed bug with per-Transfer data size specification
- Fixed bug when using XCC prefered table


## v1.58.00
### Fixed
- Fixed broken specific DMA-engine copies

## v1.57.01
### Added
- Re-added "scaling" GPU GFX preset benchmark, which tests copies from GPU to other devices using varying
  number of CUs.

## v1.57.00
### Modified
- Removing use of default starship operator / C++20 requirement to enable compilation of more OSs
- Changing how version is reported.  Client version is now just last two digits, and increments only if
  no changes are made to the backend header-only library file, and resets to 0 when header is updated
- GFX_SINGLE_TEAM=0 is set by default

## v1.56
### Fixed
- Fixed bug when using interactive mode.  Interactive mode now starts prior to all warmup iterations

## v1.55
### Fixed
- Fixed missing header error when compiling on CentOS
- Fixed issues when using multi-stream mode for GFX executor

## v1.54
### Modified
- Refactored TransferBench into a header-only library combined with a thin client to facilitate the
  use of TransferBench as the backend for other applications
- Optimized how data validation is handled - this should speed up Tests with many parallel transfers as data is only
  generated once
- Preset benchmarks now no longer take in any extra command line arguments.  Preset settings are only accessed via
  environment variables.  Details for each preset are printed
- The a2a preset benchmark now defaults to using fine-grained memory and GFX unroll of 2
- Refactored how Transfers are launched in parallel which has reduced some CPU-side overheads
- CPU and DMA executor timing now use CPU wall clock timing instead of slowest Transfer time
### Added
- New one2all preset which sweeps over all subests of parallel transfers from one GPU to others
- Adding new warnings for DMA execution relating to how HIP will default to using agents from the source memory
### Removed
- CU scaling preset has been removed.  Similar functionality already exists in the schmoo preset benchmark
- Preparation of source data via GFX kernel has been removed (USE_PREP_KERNEL)
- Removed GFX block-reordering (BLOCK_ORDER)
- Removed NUM_CPU_DEVICES and NUM_GPU_DEVICES from common env vars and only into the presets they apply to.
- Removed SHARED_MEM_BYTES option for GFX executor
- Removed USE_PCIE_INDEX, and SHARED_MEM_BYTES
### Fixed
- Fixed a potential timing reporting issue when DMA executed Transfers end up getting serialized.

## v1.53
### Added
- Added ability to specify NULL for sweep preset as source or destination memory type

## v1.52
### Added
- Added USE_HSA_DMA env var to switch to using hsa_amd_memory_async_copy instead of hipMemcpyAsync for DMA execution
- Added ability to set USE_GPU_DMA env var for a2a benchmark
- Adding check for large BAR enablement for GPU devices during topology check
### Fixed
- Potential memory leak if HSA reports 0 hops between GPUs and CPUs

## v1.51

## Modified
- CSV output has been modified slightly to match normal terminal output
- Output for non single stream mode has been changed to match single stream mode (results per Executor)

### Added
- Support for sub-iterations via NUM_SUBITERATIONS.  This allows for additional looping during an iteration
  If set to 0, this should infinitely loop (which may be useful for some debug purposes)
- Support for variable number of subexecutors (currently for GPU-GFX executor only).  Setting subExecutors to
  0 will run over a range of CUs to use, and report only the results of the best one found. This can be tuned
  for performance by setting the MIN_VAR_SUBEXEC and MAX_VAR_SUBEXEC environment variables to narrow the
  search space.  The number of CUs used will be identical for all variable subExecutor transfers
- Experimental new "healthcheck" preset config which currently only supports MI300 series.  This preset runs
  through CPU to GPU bandwidth tests and all-to-all XGMI bandwidth tests and compares against expected values
  Pass criteria limits can be modified (due to platform differences) via the environment variables
  LIMIT_UDIR (undirectional), LIMIT_BDIR (bidirectional), and LIMIT_A2A (Per GPU-GPU link bandwidth)

### Fixed
- Fixed out-of-bounds memory access during topology detection that can happen if the number of
  CPUs is less than the number of NUMA domains
- Fixed CU masking functionality on multi-XCD architectures (e.g. MI300)

## v1.50

### Added
- Adding new parallel copy preset benchmark (pcopy)
  - Usage: ./TransferBench pcopy <numBytes=64M> <#CUs=8> <srcGpu=0> <minGpus=1> <maxGpus=#GPU-1>
### Fixed
- Removed non-copies DMA Transfers (this had previously been using hipMemset)
- Fixed CPU executor when operating on null destination

## v1.49

### Fixes
* Enumerating previously missed DMA engines used only for CPU traffic in topology display

## v1.48

### Fixes
* Various fixes for TransferBenchCuda

### Additions
* Support for targeting specific DMA engines via executor subindex (e.g. D0.1)
* Printing warnings when exeuctors are overcommited

### Modifications
* USE_REMOTE_READ supported for rwrite preset benchmark

## v1.47

### Fixes
* Fixing CUDA support

## v1.46

### Fixes
* Fixing GFX_UNROLL set to 13 (past 8) on gfx906 cards

### Modifications
* GFX_SINGLE_TEAM=1 by default
* Adding field showing summation of individual Transfer bandwidths for Executors

## v1.45

### Additions
* Adding A2A_MODE to a2a preset (0 = copy, 1 = read-only, 2 = write-only)
* Adding GFX_UNROLL to modify GFX kernel's unroll factor
* Adding GFX_WAVE_ORDER to modify order in which wavefronts process data

### Modifications
* Rewrote the GFX reduction kernel to support new wave ordering

## v1.44

### Additions
* Adding rwrite preset to benchmark remote parallel writes
 * Usage: ./TransferBench rwrite <numBytes=64M> <#CUs=8> <srcGpu=0> <minGpus=1> <maxGpus=3>

## v1.43

### Changes
* Modifying a2a to show executor timing, as well as executor min/max bandwidth

## v1.42

### Fixes
* Fixing schmoo maxNumCus optional arg parsing
* Schmoo output modified to be easier to copy

## v1.41

### Additions
* Adding schmoo preset config benchmarks local/remote reads/writes/copies
  * Usage: ./TransferBench schmoo <numBytes=64M> <localIdx=0> <remoteIdx=1> <maxNumCUs=32>

### Fixes
* Fixing some misreported timings when running with non-fixed number of iterations

## v1.40

### Fixes
* Fixing XCC defaulting to 0 instead of random for preset configs, ignoring XCC_PREF_TABLE

## v1.39

### Additions
* (Experimental) Adding support for Executor sub-index
### Fixes
- Remove deprecated gcnArch code.  ROCm version must include support for hipDeviceMallocUncached

## v1.38

### Fixes
* Adding missing threadfence which could cause non-fine-grained Transfers to report higher speeds

## v1.37

### Changes
* USE_SINGLE_STREAM is enabled by default now.  (Disable via USE_SINGLE_STREAM=0)

### Fixes
* Fix unrecognized token error when XCC_PREF_TABLE is unspecified

## v1.36

### Additions

* (Experimental) Adding XCC filtering - combined with XCC_PREF_TABLE, this tries to select
  specific XCCs to use for specific (SRC->DST) Transfers

## v1.35

### Additions

* USE_FINE_GRAIN also applies to a2a preset

## v1.34

### Additions

* Set `GPU_KERNEL=3` as default for gfx942

## v1.33

### Additions

* Added the `ALWAYS_VALIDATE` environment variable to allow for validation after every iteration, instead
  of only once at the end of all iterations

## v1.32

### Changes

* Increased the line limit from 2048 to 32768

## v1.31

### Changes

* `SHOW_ITERATIONS` now shows XCC:CU instead of just CU ID
* `SHOW_ITERATIONS` is printed when `USE_SINGLE_STREAM`=1

## v1.30

### Additions

* `BLOCK_SIZE` has been added to control the threadblock size (must be a multiple of 64, up to 512)
* `BLOCK_ORDER` has been added to control how work is ordered for GFX-executors running
  `USE_SINGLE_STREAM`=1
  * 0 - Threadblocks for transfers are ordered sequentially (default)
  * 1 - Threadblocks for transfers are interleaved
  * 2 - Threadblocks for transfers are ordered randomly

## v1.29

### Additions

* A2A preset config now responds to `USE_REMOTE_READ`

### Fixes

* Race-condition during wall-clock initialization caused "inf" during single-stream runs
* CU numbering output after CU masking

### Changes

* The default number of warmups has been reverted to 3
* The default unroll factor for gfx940/941 has been set to 6

## v1.28

### Additions

* Added `A2A_DIRECT`, which only runs all-to-all on directly connected GPUs (now on by default)
* Added average statistics for P2P and A2A benchmarks
* Added `USE_FINE_GRAIN` for P2P benchmark
  * With older devices, P2P performance with default coarse-grain device memory stops timing as soon
    as a request is sent to data fabric, and not actually when it arrives remotely. This can artificially
    inflate bandwidth numbers, especially when sending small amounts of data.

### Changes

* Modified P2P output to help distinguish between CPU and GPU devices

### Fixes

* Fixed Makefile target to prevent unnecessary re-compilation

## v1.27

### Additions

* Added cmdline preset to allow specification of  simple tests on command line (e.g.,
  `./TransferBench cmdline 64M "1 4 G0->G0->G1"`)
* Adding the `HIDE_ENV` environment variable, which stops environment variable values from printing
* Adding the `CU_MASK` environment variable, which allows you to select the CUs to run on
* `CU_MASK` is specified in CU indices (0-#CUs-1), where ' - ' can be used to denote ranges of values
  (e.g., `CU_MASK`=3-8,16 requests that transfer be run only on CUs 3,4,5,6,7,8,16)
  * Note that this is somewhat experimental and may not work on all hardware
* `SHOW_ITERATIONS` now shows CU usage for that iteration (experimental)

### Changes

* Added extra comments on commonly missing includes with details on how to install them

### Fixes

* CUDA compilation works again (the `wall_clock64` CUDA alias was not defined)

## v1.26

### Additions

* Setting SHOW_ITERATIONS=1 provides additional information about per-iteration timing for file and
  P2P configs
  * For file configs, iterations are sorted from min to max bandwidth and displayed with standard
    deviation
  * For P2P, min/max/standard deviation is shown for each direction

### Changes

* P2P benchmark formatting now reports bidirectional bandwidth in each direction (as well as sum) for
  clarity

## v1.25

### Fixes

* Fixed a bug in the P2P bidirectional benchmark that used the incorrect number of `subExecutors` for
  CPU<->GPU tests

## v1.24

### Additions

* New All-To-All GPU benchmark accessed by preset "A2A"
* Added gfx941 wall clock frequency

## v1.23

### Additions

* New GPU subexec scaling benchmark accessed by preset "scaling"
  * Tests GPU-GFX copy performance based on # of CUs used

## v1.22

### Changes

* Switched the kernel timing function to `wall_clock64`

## v1.21

### Fixes

* Fixed a bug with `SAMPLING_FACTOR`

## v1.20

### Fixes

* `VALIDATE_DIRECT` can now be used with `USE_PREP_KERNEL`
* Switched to local GPU for validating GPU memory

## v1.19

### Additions

* `VALIDATE_DIRECT` now also applies to source memory array checking
* Added null memory pointer check prior to deallocation

## v1.18

### Additions

* Adding the ability to validate GPU destination memory directly without going through the CPU
  staging buffer (`VALIDATE_DIRECT`)
  * Note that this only works on AMD devices with large-bar access enabled, and may slow things down
    considerably

### Changes

* Refactored how environment variables are displayed
* Mismatch stops after the first detected error within an array instead of listing all mismatched
  elements

## v1.17

### Additions

* Allowed switch to GFX kernel for source array initialization (`USE_PREP_KERNEL`)
  * Note that `USE_PREP_KERNEL` can't be used with `FILL_PATTERN`
* Added the ability to compile with nvcc only (`TransferBenchCuda`)

### Changes

* The default pattern was set to [Element i = ((i * 517) modulo 383 + 31) * (srcBufferIdx + 1)]

### Fixes

* Added the `example.cfg` file

## v1.16

### Additions

* Additional src array validation during preparation
* Added a new environment variable (`CONTINUE_ON_ERROR`) to resume tests after a mis-match
  detection
* Initialized GPU memory to 0 during allocation

## v1.15

### Fixes

* Fixed a bug that prevented single transfers greater than 8 GB

### Changes

* Removed "check for latest ROCm" warning when allocating too much memory
* Off-source memory value is now printed when a mis-match is detected

## v1.14

### Additions

* Added documentation
* Added pthread linking in src/Makefile and CMakeLists.txt
* Added printing off the hex value of the floats for output and reference

## v1.13

### Additions

* Added support for cmake

### Changes

* Converted to the Pitchfork layout standard

## v1.12

### Additions

* Added support for TransferBench on NVIDIA platforms (via `HIP_PLATFORM`=nvidia)
  * Note that CPU executors on NVIDIA platform cannot access GPU memory (no large-bar access)

## v1.11

### Additions

* Added multi-input/multi-output (MIMO) support: transfers now can reduce (element-wise summation)
  multiple input memory arrays and write sums to multiple outputs
* Added GPU-DMA executor 'D', which uses `hipMemcpy` for SDMA copies
  * Previously, this was done using `USE_HIP_CALL`, but now GPU-GFX kernel can run in parallel with
    GPU-DMA, instead of applying to all GPU executors globally
  * GPU-DMA executor can only be used for single-input/single-output transfers
  * GPU-DMA executor can only be associated with one SubExecutor
* Added new "Null" memory type 'N', which represents empty memory. This allows for read-only or
  write-only transfers
* Added new `GPU_KERNEL` environment variable that allows switching between various GPU-GFX
  reduction kernels

### Optimizations

* Improved GPU-GFX kernel performance based on hardware architecture when running with
  fewer CUs

### Changes

* Updated the `example.cfg` file to cover new features
* Updated output to support MIMO
* Changed CU and CPU thread naming to SubExecutors for consistency
* Sweep Preset: default sweep preset executors now includes DMA
* P2P benchmarks:
  * Removed `p2p_rr`, `g2g` and `g2g_rr` (now only works via P2P)
    * Setting `NUM_CPU_DEVICES`=0 can only be used to benchmark GPU devices (like `g2g`)
    * The new `USE_REMOTE_READ` environment variable replaces `_rr` presets
  * New environment variable `USE_GPU_DMA`=1 replaces `USE_HIP_CALL`=1 for benchmarking with
    GPU-DMA Executor
  * Number of GPU SubExecutors for benchmark can be specified via `NUM_GPU_SE`
    * Defaults to all CUs for GPU-GFX, 1 for GPU-DMA
  * Number of CPU SubExecutors for benchmark can be specified via `NUM_CPU_SE`
* Psuedo-random input pattern has been slightly adjusted to have different patterns for each input
  array within same transfer

### Removals

* `USE_HIP_CALL`: use `GPU-DMA` executor 'D' or set `USE_GPU_DMA`=1 for P2P
  benchmark presets
  * Currently, a warning will be issued if `USE_HIP_CALL` is set to 1 and the program will stop
* `NUM_CPU_PER_TRANSFER`: the number of CPU SubExecutors will be whatever is specified for the
  transfer
* `USE_MEMSET`: this function can now be done via a transfer using the null memory type

## v1.10

### Fixes

* Fixed incorrect bandwidth calculation when using single stream mode and per-transfer data sizes

## v1.09

### Additions

* Printing off src/dst memory addresses during interactive mode

### Changes

* Switching to `numa_set_preferred` instead of `set_mempolicy`

## v1.08

### Changes

* Fixed handling of non-configured NUMA nodes
* Topology detection now shows actual NUMA node indices
* Fixed 'for' issue with `NUM_GPU_DEVICES`

## v1.07

### Fixes

* Fixed bug with allocations involving non-default CPU memory types

## v1.06

### Additions

* Unpinned CPU memory type ('U'), which may require `HSA_XNACK`=1 in order to access via
  GPU executors
* Added sweep configuration logging to `lastSweep.cfg`
* Ability to specify the number of CUs to use for sweep-based presets

### Changes

* Modified advanced configuration file format to accept bytes-per-transfer

### Fixes

* Fixed random sweep repeatability
* Fixed bug with CPU NUMA node memory allocation

## v1.05

### Additions

* Topology output now includes NUMA node information
* Support for NUMA nodes with no CPU cores (e.g., CXL memory)

### Removals

* The `SWEEP_SRC_IS_EXE` environment variable was removed

## v1.04

### Additions

* There are new environment variables for sweep based presets:
  * `SWEEP_XGMI_MIN`: The minumum number of XGMI hops for transfers
  * `SWEEP_XGMI_MAX`: The maximum number of XGMI hops for transfers
  * `SWEEP_SEED`: Uses a random seed
  * `SWEEP_RAND_BYTES`: Uses a random amount of bytes (up to pre-specified N) for each transfer

### Changes

* CSV output for sweep now includes an environment variables section followed by output
* CSV output no longer lists environment variable parameters in columns
* We changed the default number of warmup iterations from 3 to 1
* Split CSV output of link type to `ExeToSrcLinkType` and `ExeToDstLinkType`

## v1.03

### Additions

* There are new preset modes stress-test benchmarks: `sweep` and `randomsweep`
  * `sweep` iterates over all possible sets of transfers to test
  * `randomsweep` iterates over random sets of transfers
  * New sweep-only environment variables can modify `sweep`
    * `SWEEP_SRC`: String containing only "B","C","F", or "G" that defines possible source memory types
    * `SWEEP_EXE`: String containing only "C" or "G" that defines possible executors
    * `SWEEP_DST`: String containing only "B","C","F", or "G" that defines possible destination memory types
    * `SWEEP_SRC_IS_EXE`: Restrict the executor to be the same as the source, if non-zero
    * `SWEEP_MIN`: Minimum number of parallel transfers to test
    * `SWEEP_MAX`: Maximum number of parallel transfers to test
    * `SWEEP_COUNT`: Maximum number of tests to run
    * `SWEEP_TIME_LIMIT`: Maximum number of seconds to run tests
* New environment variables to restrict number of available devices to test on (primarily for sweep
  runs)
  * `NUM_CPU_DEVICES`: Number of CPU devices
  * `NUM_GPU_DEVICES`: Number of GPU devices

### Fixes

* Fixed timing display for CPU executors when using single-stream mode

## v1.02

### Additions

* Setting `NUM_ITERATIONS` to a negative number indicates a run of -`NUM_ITERATIONS` seconds per
  test

### Changes

* Copies are now referred to as 'transfers' instead of 'links'
* Reordered how environment variables are displayed (alphabetically now)

### Removals

* Combined timing is now always on for kernel-based GPU copies; the `COMBINED_TIMING`
  environment variable has been removed
* Single sync is no longer supported for facility variable iterations; the `USE_SINGLE_SYNC`
  environmental variable has been removed

## v1.01

### Additions

* Added the `USE_SINGLE_STREAM` feature
  * All Links that run on the same GPU device are run with a single kernel launch on a single stream
  * This doesn't work with `USE_HIP_CALL`, and it forces `USE_SINGLE_SYNC` to collect timings
  * Added the ability to request coherent or fine-grained host memory ('B')

### Changes

* Separated the TransferBench repository from the RCCL repository
* Peer-to-peer benchmark mode now works with `OUTPUT_TO_CSV`
* Toplogy display now works with `OUTPUT_TO_CSV`
* Moved the documentation about the config file into `example.cfg`

### Removals

* Removed config file generation
* Removed the 'show pointer address' (`SHOW_ADDR`) environment variable