CPU environment and admission

Classes
struct	ftz::native_fp_state
	Opaque native control/status snapshot, suitable for exact restoration checks. More...
struct	ftz::native_fp32_scope
	Borrows the calling thread with RNE, masked exceptions and selected denormal controls. Saves and restores complete control/status state. The object and its nested external scopes must be destroyed on their constructing thread. It cannot be copied or moved. Construction throws on invalid/unavailable controls when exceptions are enabled; otherwise it terminates. Destruction is noexcept. More...
struct	ftz::ftz32_cpu_admission
	Results of finite startup witnesses for this scalar compilation and calling thread. These observations are not an exhaustive proof of every arithmetic input. More...

Enumerations
enum class	ftz::native_fp32_mode
	Selects gradual denormals or signed native input/output flushing.
enum class	ftz::ftz32_cpu_failure
	Identifies the first rejected admission requirement.

Functions
template<ftz32_type T = ftz32>
ftz32_cpu_admission	ftz::probe_ftz32_cpu ()
	Observes whether this compiled scalar profile meets the requested policy.
bool	ftz::native_fp32_environment_available () noexcept
	Reports whether this build can access native CPU FP controls; this is not numerical admission.
native_fp_state	ftz::read_native_fp_state () noexcept
	Reads this thread's controls and status without changing them; unsupported hosts return zero fields.
bool	ftz::set_native_fp32_mode (native_fp32_mode mode) noexcept
	Initializes an application-owned numerical thread, without restoration or admission.

Detailed Description

Controls are local to the calling CPU thread. They neither enable an ISA nor configure a GPU. Establish the environment on every numerical worker and qualify the compiled profile explicitly; ordinary arithmetic never probes it.

  ftz::native_fp32_scope region(ftz::native_fp32_mode::flush);
  auto admission = ftz::probe_ftz32_cpu<ftz::h32>();
  if (!admission.admitted()) return false;
  // Establish this agreement on each numerical thread. Run qualification at startup.
  auto value = ftz::h32(2.f) * ftz::h32(3.f);
  {
    ftz::native_fp32_scope::external_scope external(region);
    // Call third-party code here under the environment preceding region.
    if (ftz::read_native_fp_state() != region.previous()) return false;
  }
  // The numerical region is restored, including its saved status flags.
  return region.controls_match() && value.to_bits() == 0x40c00000u;

  if (!ftz::set_native_fp32_mode(ftz::native_fp32_mode::flush)) return false;
  // This establishes RNE and masked exceptions, and clears status flags.
  // It does not run admission or restore the previous state on return.
  return true;

Function Documentation

probe_ftz32_cpu()

template<ftz32_type T = ftz32>

ftz32_cpu_admission ftz::probe_ftz32_cpu ( )

inlinenodiscardexport

Observes whether this compiled scalar profile meets the requested policy.

Template Parameters

T	m32 or h32; the default is the configured compatibility alias. Call at startup in the intended environment. The probe does not change controls or qualify CPU ISA/OS vector state, another thread, a GPU, or every math input. Masked status flags may change; use native_fp32_scope to restore the caller.

Returns

Witness results; admitted() reports the selected policy's admission.

  ftz::native_fp32_scope region(ftz::native_fp32_mode::flush);
  auto admission = ftz::probe_ftz32_cpu<ftz::h32>();
  if (!admission.admitted()) return false;
  // Establish this agreement on each numerical thread. Run qualification at startup.
  auto value = ftz::h32(2.f) * ftz::h32(3.f);
  {
    ftz::native_fp32_scope::external_scope external(region);
    // Call third-party code here under the environment preceding region.
    if (ftz::read_native_fp_state() != region.previous()) return false;
  }
  // The numerical region is restored, including its saved status flags.
  return region.controls_match() && value.to_bits() == 0x40c00000u;

Definition at line 706 of file ftz.ccm.