Vc
0.7.5-dev
SIMD Vector Classes for C++
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A helper class to simplify usage of correctly aligned and padded memory, allowing both vector and scalar access.
Example:
This code allocates a small array and implements three equivalent loops (that do nothing useful). The loops show how scalar and vector read/write access is best implemented.
Since the size of 11 is not a multiple of int_v::Size (unless you use the scalar Vc implementation) the last write access of the vector loop would normally be out of bounds. But the Memory class automatically pads the memory such that the whole array can be accessed with correctly aligned memory addresses.
V | The vector type you want to operate on. (e.g. float_v or uint_v) |
Size | The number of entries of the scalar base type the memory should hold. This is thus the same number as you would use for a normal C array (e.g. float mem[11] becomes Memory<float_v, 11> mem). |
#include <Vc/Memory>
Inherits VectorAlignedBaseT< V >, and MemoryBase< V, Memory< V, Size, 0u >, 1, void >.
Public Member Functions | |
constexpr size_t | entriesCount () const |
constexpr size_t | vectorsCount () const |
VectorPointerHelper< V, AlignedFlag > | vector (size_t i) |
const VectorPointerHelperConst < V, AlignedFlag > | vector (size_t i) const |
Const overload of the above function. | |
VectorPointerHelper< V, UnalignedFlag > | vector (size_t i, int shift) |
const VectorPointerHelperConst < V, UnalignedFlag > | vector (size_t i, int shift) const |
Const overload of the above function. | |
VectorPointerHelper< V, A > | vectorAt (size_t i, A align=Vc::Aligned) |
const VectorPointerHelperConst < V, A > | vectorAt (size_t i, A align=Vc::Aligned) const |
Const overload of the above function. | |
VectorPointerHelper< V, AlignedFlag > | firstVector () |
const VectorPointerHelperConst < V, AlignedFlag > | firstVector () const |
Const overload of the above function. | |
VectorPointerHelper< V, AlignedFlag > | lastVector () |
const VectorPointerHelperConst < V, AlignedFlag > | lastVector () const |
Const overload of the above function. |
Static Public Member Functions | |
static Memory< V, Size, 0u > & | fromRawData (EntryType *ptr) |
Wrap existing data with the Memory convenience class. |
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static |
Wrap existing data with the Memory convenience class.
This function returns a reference to a Memory<V, Size, 0> object that you must capture to avoid a copy of the whole data:
ptr | An aligned pointer to memory of type V::EntryType (e.g. float for Vc::float_v). |
ptr
passed to this function must be aligned according to the alignment restrictions of V
. Size
. This includes the required padding at the end to allow the last entries to be accessed via vectors. If you know what you are doing you might violate this constraint. constexpr size_t entriesCount | ( | ) | const |
Reimplemented from MemoryBase< V, Memory< V, Size, 0u >, 1, void >.
constexpr size_t vectorsCount | ( | ) | const |
Reimplemented from MemoryBase< V, Memory< V, Size, 0u >, 1, void >.
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inherited |
i | Selects the offset, where the vector should be read. |
i-th
vector in the memory.The return value can be used as any other vector object. I.e. you can substitute something like
with
This function ensures that only aligned loads and stores are used. Thus it only allows to access memory at fixed strides. If access to known offsets from the aligned vectors is needed the vector(size_t, int) function can be used.
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inherited |
Const overload of the above function.
i | Selects the offset, where the vector should be read. |
i-th
vector in the memory.
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inherited |
i-th
vector + shift
in the memory.This function ensures that only unaligned loads and stores are used. It allows to access memory at any location aligned to the entry type.
i | Selects the memory location of the i-th vector. Thus if V::Size == 4 and i is set to 3 the base address for the load/store will be the 12th entry (same as &mem [12]). |
shift | Shifts the base address determined by parameter i by shift many entries. Thus vector(3, 1) for V::Size == 4 will load/store the 13th - 16th entries (same as &mem [13]). |
V::Size
will not result in aligned loads. You have to use the above vector(size_t) function for aligned loads instead.i
to 0 and use shift
as the parameter to select the memory address:
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inherited |
i-th
scalar entry in the memory.Example:
i | Specifies the scalar entry from where the vector will be loaded/stored. I.e. the values scalar(i), scalar(i + 1), ..., scalar(i + V::Size - 1) will be read/overwritten. |
align | You must take care to determine whether an unaligned load/store is required. Per default an aligned load/store is used. If i is not a multiple of V::Size you must pass Vc::Unaligned here. |
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inherited |
Const overload of the above function.
i-th
scalar entry in the memory.i | Specifies the scalar entry from where the vector will be loaded/stored. I.e. the values scalar(i), scalar(i + 1), ..., scalar(i + V::Size - 1) will be read/overwritten. |
align | You must take care to determine whether an unaligned load/store is required. Per default an aligned load/store is used. If i is not a multiple of V::Size you must pass Vc::Unaligned here. |
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inherited |
This function is simply a shorthand for vector(0).
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inherited |
This function is simply a shorthand for vector(vectorsCount() - 1).