Table of Contents

Class DTypeMeta

Namespace
NumSharp
Assembly
NumSharp.dll

The DType CLASS — NumPy's PyArray_DTypeMeta (type(np.dtype('f8')), i.e. np.dtypes.Float64DType). One live object per dtype class; a DType is an INSTANCE of it (the descriptor). This is NEP 41/42's two-level model: behaviour lives on the class as virtual "slots" (CommonDType(DTypeMeta), CommonInstance(DType, DType), DefaultDescr(), EnsureCanonical(DType), DiscoverDescrFromObject(object), IsKnownScalarType(Type), the casting implementations), parameters live on the instance (a datetime unit, a byte order).

public abstract class DTypeMeta
Inheritance
DTypeMeta
Derived
Inherited Members

Remarks

Compatibility contract. NPTypeCode stays the storage / kernel discriminator: every meta that has storage exposes it as TypeCode, and a future storage-backed dtype adds one enum member and registers it here — the enum is an optimisation the registry hands out, not the identity. A meta without storage (DatetimeDTypeMeta in Stage A) has TypeCode == Empty; allocating storage for its descriptors raises NotSupportedException naming the missing piece.

Type numbers follow NumPy's NPY_TYPES (LP64 convention: Int32 = NPY_INT (5), Int64 = NPY_LONG (7), Half = 23, DateTime = 21, TimeDelta = 22); the two NumSharp-only dtypes take the user-defined range (Decimal = 256, Char = 257), which is also what makes their descriptors report isbuiltin == 2. The number ORDER is load-bearing: the builtin common_dtype defers to the operand with the larger type number ("the more generic one handles it"), exactly as NumPy's default_builtin_common_dtype does.

NotImplemented is spelled null: CommonDType(DTypeMeta) returns null when this class does not know the other one, and CommonDType(DTypeMeta, DTypeMeta) then asks the other class (NEP 42's two-sided __common_dtype__ protocol) before raising DTypePromotionError.

NEP 55 reservations. HasReferences, GetClearLoop(DType) and GetFillZeroLoop(DType) are the slots a reference-holding dtype (StringDType) will override; the builtins report false / null.

Constructors

DTypeMeta(string, string, int, Type, string, NPTypeCode, char, char, int, int, DTypeFlags, IReadOnlyList<string>)

Builds a DType class. Called by the registry / subclasses only — every class is a singleton reachable via DTypeRegistry and np.dtypes.

protected DTypeMeta(string name, string modulePath, int typeNum, Type scalarType, string scalarName, NPTypeCode typeCode, char kind, char typeChar, int itemSize, int alignment, DTypeFlags flags, IReadOnlyList<string> aliases = null)

Parameters

name string

NumPy's class name ("Int32DType", "DateTime64DType", "_PyLongDType").

modulePath string

The module the class lives in — "numpy.dtypes" for the NumPy-mirrored classes, "numsharp.dtypes" for the NumSharp-only ones — so ToString() renders NumPy's <class 'numpy.dtypes.Int32DType'>.

typeNum int

NumPy's type_num (see the class remarks); -1 for abstract classes.

scalarType Type

The C# scalar type of one element (typeof(int)); null when there is none yet.

scalarName string

NumPy's dtype.type.name ("int32", "datetime64", "decimal").

typeCode NPTypeCode

The storage discriminator, Empty when the class has no storage.

kind char

NumPy's dtype.kind character ('b' 'i' 'u' 'f' 'c' 'M' 'm' 'U').

typeChar char

NumPy's dtype.char ('?' 'b' 'B' 'h' 'H' 'i' 'I' 'l' 'L' 'e' 'f' 'd' 'D' 'M' 'm').

itemSize int

Element size in bytes (-1 for abstract classes).

alignment int

Required alignment in bytes (NumPy's dtype.alignment).

flags DTypeFlags

The DTypeFlags (legacy / abstract / parametric / numeric).

aliases IReadOnlyList<string>

Alias class names NumPy also exports ("IntDType" for Int32DType).

Properties

Aliases

Alias class names NumPy also exports for this class (e.g. ByteDType for Int8DType).

public IReadOnlyList<string> Aliases { get; }

Property Value

IReadOnlyList<string>

Alignment

Required alignment in bytes.

public int Alignment { get; }

Property Value

int

Flags

The class flags.

public DTypeFlags Flags { get; }

Property Value

DTypeFlags

FullName

The fully qualified class name: "numpy.dtypes.Int32DType".

public string FullName { get; }

Property Value

string

HasReferences

Whether items of this dtype hold references that must be cleared (NumPy's NPY_ITEM_REFCOUNT); false for every builtin.

public virtual bool HasReferences { get; }

Property Value

bool

HasStorage

True when descriptors of this class can back an NDArray today (a storage NPTypeCode exists).

public bool HasStorage { get; }

Property Value

bool

IsAbstract

An abstract dtype (no instances; promotion only).

public bool IsAbstract { get; }

Property Value

bool

IsLegacy

A legacy (pre-NEP 41 layout) dtype — every builtin and the datetime pair.

public bool IsLegacy { get; }

Property Value

bool

IsNumeric

A numeric dtype (bool, integer, float, complex).

public bool IsNumeric { get; }

Property Value

bool

IsParametric

A parametric dtype (instances carry parameters — a unit, a length).

public bool IsParametric { get; }

Property Value

bool

ItemSize

Element size in bytes (-1 for abstract classes).

public int ItemSize { get; }

Property Value

int

Kind

NumPy's dtype.kind character ('b' bool, 'i'/'u' integers, 'f', 'c', 'M', 'm', 'U').

public char Kind { get; }

Property Value

char

ModulePath

The module path used in ToString(): "numpy.dtypes" or "numsharp.dtypes".

public string ModulePath { get; }

Property Value

string

Name

NumPy's class name: "Int32DType", "DateTime64DType", "_PyLongDType".

public string Name { get; }

Property Value

string

ScalarName

NumPy's dtype.type.name: "int32", "bool", "datetime64", "decimal".

public string ScalarName { get; }

Property Value

string

ScalarType

The C# scalar type of one element (NumPy's DType.type); null when the class has no C# scalar yet.

public Type ScalarType { get; }

Property Value

Type

Singleton

The canonical native descriptor of a non-parametric class — NumPy's DType.singleton, the object np.dtype('i8') returns every time (np.dtype('i8') is np.dtype('i8')). Null for abstract classes; for the parametric datetime pair it is the generic-unit descriptor and DefaultDescr() hands out COPIES of it (a copy reports isbuiltin == 0, as in NumPy).

public DType Singleton { get; }

Property Value

DType

TypeChar

NumPy's dtype.char — the unique one-character type code.

public char TypeChar { get; }

Property Value

char

TypeCode

The storage / kernel discriminator; Empty when the class has no storage.

public NPTypeCode TypeCode { get; }

Property Value

NPTypeCode

TypeNum

NumPy's type_num (NPY_TYPES, LP64 convention; 256+ for the NumSharp-only dtypes; -1 for abstract).

public int TypeNum { get; }

Property Value

int

WithinDTypeCastingImpl

The casting implementation between two instances of this class (within_dtype_castingimpl).

public CastingImpl WithinDTypeCastingImpl { get; }

Property Value

CastingImpl

Methods

CommonDType(DTypeMeta)

common_dtype: the class that can hold values of both this class and other, or null (NumPy's NotImplemented) when this class does not know the other — the caller then asks other the mirrored question.

public abstract DTypeMeta CommonDType(DTypeMeta other)

Parameters

other DTypeMeta

Returns

DTypeMeta

CommonInstance(DType, DType)

common_instance: for a PARAMETRIC class, the descriptor that can hold values of two descriptors of this class (the unit GCD for datetimes; the longer length for strings). Non-parametric classes return their default descriptor.

public virtual DType CommonInstance(DType descr1, DType descr2)

Parameters

descr1 DType
descr2 DType

Returns

DType

DefaultDescr()

default_descr: the descriptor a bare class stands for — the singleton for the builtins, a fresh generic-unit descriptor for datetime64 / timedelta64, the default (int64/float64/complex128) for the abstract NEP 50 scalar classes.

public abstract DType DefaultDescr()

Returns

DType

DiscoverDescrFromObject(object)

discover_descr_from_pyobject: the descriptor a scalar of this class should get (the default for every non-parametric class).

public virtual DType DiscoverDescrFromObject(object obj)

Parameters

obj object

Returns

DType

EnsureCanonical(DType)

ensure_canonical: the native-byte-order form of descr (the descriptor itself when already native).

public virtual DType EnsureCanonical(DType descr)

Parameters

descr DType

Returns

DType

GetCastingImpl(DTypeMeta)

The CastingImpl from this class to to (the within-dtype implementation when to is this class), or null when no cast exists — NumPy's PyArray_GetCastingImpl.

public CastingImpl GetCastingImpl(DTypeMeta to)

Parameters

to DTypeMeta

Returns

CastingImpl

GetClearLoop(DType)

get_clear_loop: a loop that releases the references an item holds; null when HasReferences is false.

public virtual NDInnerLoopFunc GetClearLoop(DType descr)

Parameters

descr DType

Returns

NDInnerLoopFunc

GetFillZeroLoop(DType)

get_fill_zero_loop: a loop that writes this dtype's zero; null when a zeroed buffer already is the zero.

public virtual NDInnerLoopFunc GetFillZeroLoop(DType descr)

Parameters

descr DType

Returns

NDInnerLoopFunc

Instantiate()

The NumPy class call Int8DType(): the no-argument instantiation returns the singleton for a non-parametric legacy class, and raises NumPy's TypeError for a parametric one (DateTime64DType() → "Preliminary-API: Flexible/Parametric legacy DType … can only be instantiated using np.dtype(...)"), verbatim.

public virtual DType Instantiate()

Returns

DType

IsKnownScalarType(Type)

is_known_scalar_type: whether a C# scalar of type belongs to this class.

public virtual bool IsKnownScalarType(Type type)

Parameters

type Type

Returns

bool

ToString()

NumPy's rendering of the class object: <class 'numpy.dtypes.Int32DType'>.

public override string ToString()

Returns

string
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