Configuration reference

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Every setting that affects Tessero, by where it is set.

php.ini: extension

Setting	Default	Scope	Effect
`extension=tessero`		php.ini	loads ext-tessero
`tessero.threads`	`1`	`PHP_INI_ALL`	OpenMP threads for element-wise kernels on ≥ 131 072 elements and MDP sweeps on > 4 096 state-action pairs. Clamped to [1, 4 × cores]. 1 when built without OpenMP
`tessero.memory_budget`	`0`	`PHP_INI_ALL`	native memory cap for extension arrays and solver workspaces, bytes (`256M`, `2G` accepted). 0 = unlimited
`tessero.epsilon`	`1e-6`	`PHP_INI_ALL`	default tolerance of `Engine::mdpValueIteration`

The extension re-applies tessero.threads and tessero.memory_budget at every request start, so runtime changes last for one request.

Setting	Recommended	Effect
`ffi.enable`	`preload` (FPM), `1` or `preload` (CLI)	`preload` allows FFI only from preloaded code, plus the CLI
`opcache.enable`	`1`	required for preloading
`opcache.preload`	`…/vendor/tessero/tessero/resources/preload.php`	binds libtessero and BLAS at startup
`opcache.preload_user`	the FPM pool user	preload runs as this user
`opcache.jit`	any	all suites pass with JIT off, `function` and `tracing` (see [upstream bugs(https://github.com/DMJ-CV-91913/tessero/blob/main/docs/project/upstream-bugs.md))

Variable	Read by	Effect
`TESSERO_LIB`	FFI package, preload	absolute path of `libtessero` to load instead of the bundled binary; process environment only, refused when relative or when the file or its directory is group/world-writable
`TESSERO_BLAS`	FFI package, preload	absolute path of an LP64 OpenBLAS/LAPACKE library; same checks as `TESSERO_LIB`
`TESSERO_BLAS_THREADS`	FFI package	OpenBLAS threads (default: 1 outside the CLI)
`TESSERO_BACKEND`	Laravel	`auto`, `ext`, `ffi`
`TESSERO_THREADS`	Laravel	→ `threads`
`TESSERO_MEMORY_BUDGET`	Laravel; FFI package outside the CLI	→ `memory_budget` (bytes). The FFI package also reads it at load in non-CLI SAPIs: a positive value sets the budget, `0` or `-1` opts out of the default max(256 MiB, `memory_limit`)
`TESSERO_EPSILON`	Laravel	→ `epsilon`
`TESSERO_CAST_FORMAT`	Laravel	`json` or `binary`
`TESSERO_MAX_ELEMENTS`	Laravel	default `max_elements`
`OPENBLAS_NUM_THREADS`, `OMP_NUM_THREADS`	OpenBLAS / OpenMP runtimes	read by those libraries at load time. Prefer the Tessero settings, which apply at runtime

Key	Default	Effect
`backend`	`auto`	ext when loaded, else FFI; `ext`/`ffi` require one
`threads`	1	applied to both backends at boot and before every Octane request/task and queued job
`memory_budget`	268 435 456	bytes per process, both backends (each has its own counter)
`blas_threads`	1	OpenBLAS threads (FFI)
`epsilon`	1e-6	MDP tolerance (extension default and `Tessero::solveMdp`)
`cast_format`	`json`	default for `AsNDArray` without an argument
`max_elements`	1 000 000	default cap for request validation

FFI package	Extension	Notes
`Tessero::setThreads(n)` / `threads()`	`Engine::setMaxThreads(n)` / `getMaxThreads()`	process-wide
`Tessero::setMemoryBudget(bytes)` / `memoryBudget()`	`Engine::setMemoryBudget(bytes)` / `memoryBudget()`	process-wide
`Tessero::memoryInUse()`, `peakMemory()`	`Engine::memoryInUse()`, `peakMemory()`	bytes
`Tessero::setBlasThreads(n)`		OpenBLAS
	`Engine::setEpsilon(x)` / `getEpsilon()`
`Tessero::info()`	`Engine::info()`	diagnostics ([Monitoring(https://github.com/DMJ-CV-91913/tessero/blob/main/docs/operations/monitoring.md)); the extension also reports `memory_mapped`

Option	Where	Effect
`OPENMP=`	`make -C csrc`	build libtessero without OpenMP
`--disable-tessero-openmp`	`./configure`	build the extension without OpenMP (no libgomp)
`CC=clang`	both	compiler choice; GCC gives runtime SIMD dispatch (`target_clones`)
`-DTSR_NO_HUGE`	CFLAGS	disable transparent-huge-page hints for blocks ≥ 32 MiB