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lib/Algorithm/Classifier/IsolationForest.pm  view on Meta::CPAN

		# -O3 is the usual default: it's safe to enable unconditionally and
		# matters here -- the extended-mode oblique dot product is wrapped in
		# `#pragma omp simd`, but without aggressive optimization the compiler
		# may still emit scalar code.  Use OPTIMIZE (not CCFLAGS) -- CCFLAGS is
		# prepended to the cc line and would be shadowed by Perl's own `-O2 -g`
		# that ExtUtils::MakeMaker appends afterward (last `-O` wins in gcc).
		# IF_OPT overrides the level itself (e.g. IF_OPT=-O2 to work around a
		# miscompile, or to shorten build time while developing); it's
		# validated against a fixed set of GCC/Clang -O flags rather than
		# interpolated as-is, since this string eventually reaches a shell
		# command line via ExtUtils::MakeMaker.
		my $opt = $def_opt;
		if ( defined $ENV{IF_OPT} ) {
			if ( $ENV{IF_OPT} =~ /\A-O[0123sgz]\z/ ) {
				$opt = $ENV{IF_OPT};
			} else {
				warn "Algorithm::Classifier::IsolationForest: ignoring invalid "
					. "IF_OPT value '$ENV{IF_OPT}' (expected one of -O0 -O1 -O2 "
					. "-O3 -Os -Og -Oz); using $opt\n";
			}
		}

		# -march=<value> lets the compiler target specific instruction-set
		# extensions (AVX2 gather + FMA, etc.) for the oblique dot product
		# and the fit-time min/max scan's `#pragma omp simd` loops.
		#
		# IF_ARCH=<value> sets it explicitly (e.g. "x86-64-v3", "skylake",
		# "znver3") -- validated against a conservative identifier charset
		# since, like IF_OPT, it flows into a compiler command line.
		# IF_NATIVE=1 remains as shorthand for IF_ARCH=native and is used
		# when IF_ARCH isn't set. Prefer a specific IF_ARCH value over
		# IF_NATIVE on a machine you don't control exclusively: blanket
		# -march=native pulls in whatever the build host has, including
		# AVX-512 on some Intel CPUs, which is known to trigger clock
		# throttling under sustained heavy use and can make throughput
		# *worse* than a conservative target like x86-64-v3 (AVX2, no
		# AVX-512). Either way, the cached artefact under _Inline/ is then
		# pinned to that instruction set, so leave both unset if the
		# directory is shared across machines with different CPUs.
		my $arch = $def_arch;
		if ( defined $ENV{IF_ARCH} ) {
			if ( $ENV{IF_ARCH} eq '' or $ENV{IF_ARCH} eq 'none' ) {

				# Explicit opt-out: overrides an arch recorded at configure
				# time (there is no other way to request a plain build on
				# an install configured with IF_ARCH).
				$arch = '';
			} elsif ( $ENV{IF_ARCH} =~ /\A[A-Za-z0-9_.+=-]+\z/ ) {
				$arch = $ENV{IF_ARCH};
			} else {
				warn "Algorithm::Classifier::IsolationForest: ignoring invalid " . "IF_ARCH value '$ENV{IF_ARCH}'\n";
			}
		} elsif ( $ENV{IF_NATIVE} ) {
			$arch = 'native';
		}
		# -ffp-contract=off rides along with any -march: once the target
		# has FMA (x86-64-v3, most -march=native hosts), the compiler may
		# otherwise contract a*b+c expressions into fused multiply-adds
		# whose different rounding breaks the documented guarantee that
		# use_c => 1 and use_c => 0 build bit-identical trees (one ulp in a
		# split value cascades into a structurally different tree).  The
		# -march speedup comes from AVX2 vectorization, not contraction,
		# so this costs little (verified against the fit-determinism and
		# scoring-parity tests).
		my $opt_level = $opt;
		$opt_level .= " -march=$arch -ffp-contract=off" if length $arch;

		# IF_NO_OPENMP=1 forces the serial C build: the OpenMP compile attempt
		# is skipped, so the object has no libgomp linkage and never starts an
		# OpenMP runtime in the process.  Distinct from OMP_NUM_THREADS=1,
		# which runs the parallel code on a single thread but still loads
		# libgomp.  An explicit IF_NO_OPENMP=0 re-enables OpenMP over a
		# no-openmp configure-time default.
		my $no_omp
			= defined $ENV{IF_NO_OPENMP}
			? ( $ENV{IF_NO_OPENMP} ? 1 : 0 )
			: $def_no_omp;

		# The prebuilt object is only trusted when the effective flags match
		# what it was compiled with; any difference -- or an explicit
		# IF_RUNTIME_BUILD=1 -- falls through to the classic runtime Inline::C
		# build below, which honours the requested flags via the MD5-keyed
		# _Inline/ cache exactly as before prebuilt support existed.
		# IF_INSTALL_BUILD is the `make` rule driving the install-time compile
		# (see Makefile.PL); it must never short-circuit into loading an
		# older object.
		my $use_prebuilt
			= $prebuilt
			&& !$ENV{IF_RUNTIME_BUILD}
			&& !$ENV{IF_INSTALL_BUILD}
			&& $opt eq $def_opt
			&& $arch eq $def_arch
			&& $no_omp == $def_no_omp;

		# Inline::C hashes the C source to decide whether to rebuild but
		# does NOT include CCFLAGS / OPTIMIZE in that hash.  Without the
		# tag below, toggling IF_NATIVE/IF_ARCH/IF_OPT (or editing the
		# optimisation flags here) would silently reuse a cached binary
		# built with stale flags.  Embedding the active flags as a leading
		# comment forces the hash to differ when they change.  The OpenMP
		# and serial builds get distinct tags so they cache to separate
		# artefacts.
		my $omp_tag    = "/* if_build: openmp $opt_level */\n";
		my $serial_tag = "/* if_build: serial $opt_level */\n";

		if ( $ENV{IF_INSTALL_BUILD} ) {

			# `make` is driving: the rule Makefile.PL appended runs this load
			# with IF_INSTALL_BUILD=1 and @ARGV = (version, INST_ARCHLIB),
			# which is where Inline's install mode reads them from.  _INSTALL_
			# makes Inline compile the backend and place the shared object
			# under blib/arch so `make install` ships it; NAME/VERSION give
			# the object a fixed identity XSLoader can find at run time
			# (Inline's install mode also requires both and checks VERSION
			# against $ARGV[0]).  Same OpenMP-then-serial fallback as the
			# runtime build below.
			my @install = (
				NAME      => __PACKAGE__,
				VERSION   => $VERSION,
				_INSTALL_ => 1,
			);