Target
#include <poplar/Target.hpp>
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namespace poplar
Poplar classes and functions.
Functions
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template<>
std::uint64_t getTypeLimitsMaxAs<std::uint64_t>(const Type &t) const Get the maximum representable finite value of a given type as a std::uint64_t.
- Parameters
t – The type.
- Throws
poplar_error – if the value is not exactly representable as a std::uint64_t.
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template<>
std::int64_t getTypeLimitsMaxAs<std::int64_t>(const Type &t) const Get the maximum representable finite value of a given type as a std::int64_t.
- Parameters
t – The type.
- Throws
poplar_error – if the value is not exactly representable as a std::int64_t.
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template<>
std::uint64_t getTypeLimitsLowestAs<std::uint64_t>(const Type &t) const Get the lowest representable finite value of a given type as a std::uint64_t.
- Parameters
t – The type.
- Throws
poplar_error – if the value is not exactly representable as a std::uint64_t.
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template<>
std::int64_t getTypeLimitsLowestAs<std::int64_t>(const Type &t) const Get the lowest representable finite value of a given type as a int64_t.
- Parameters
t – The type.
- Throws
poplar_error – if the value is not exactly representable as a int64_t.
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void copyDeviceHalfToFloat(const Target &target, const void *src, float *dst, std::size_t numElements)
Convert device half-precision values to floats.
- Deprecated:
Use the poplar::convertFromDeviceType method appropriate for the data type.
- Parameters
target – The target that the half-precision data is to be copied from.
src – The pointer to the start of the half-precision data.
dst – The pointer to the float data to write.
numElements – The number of items to convert.
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void copyFloatToDeviceHalf(const Target &target, const float *src, void *dst, std::size_t numElements)
Convert float values to device half-precision values.
- Deprecated:
Use the poplar::convertToDeviceType method appropriate for the data type.
- Parameters
target – The target that the half-precision data is to be copied to.
src – The pointer to the float data to read.
dst – The pointer to the half-precision data to write.
numElements – The number of items to convert.
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void copyDeviceHalfToDouble(const Target &target, const void *src, double *dst, std::size_t numElements)
Convert device half-precision values to doubles.
- Deprecated:
Use the poplar::convertFromDeviceType method appropriate for the data type.
- Parameters
target – The target that the half-precision data is to be copied from.
src – The pointer to the start of the half-precision data.
dst – The pointer to the double precision data to write.
numElements – The number of items to convert.
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void copyDoubleToDeviceHalf(const Target &target, const double *src, void *dst, std::size_t numElements)
Convert double precision values to device half-precision values.
- Deprecated:
Use the poplar::convertToDeviceType method appropriate for the data type.
- Parameters
target – The target that the half-precision data is to be copied to.
src – The pointer to the double precision data to read.
dst – The pointer to the half-precision data to write.
numElements – The number of items to convert.
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class Target
- #include <Target.hpp>
A target representation.
The Target class holds characteristics of a compilation target and enables interaction with it.
Target creation options
ipuLinkConfiguration
(fixedWindow, slidingWindow, barleyTwist) [=fixedWindow when <=16 IPUs, otherwise slidingWindow]The configuration used for the IPU-to-IPU connections. If it is not set, Poplar decides on a configuration based on the number of IPUs.
fixedWindow: Up to 16 IPUs are supported, where each IPU can communicate with every other IPU. This is an alias to the previously named default configuration.
slidingWindow: Similar to fixedWindow, but the window of IPUs which an IPU may communicate changes. For an even indexed IPU it may send to 7 IPUs up and to 8 IPUs down, whereas an odd indexed IPU may send to 6 IPUs up and to 9 IPUs down. It is simplest when considering an IPU in the ladder configuration (see
ipuLinkTopology
), that an IPU may send up to 3 rungs up and 4 down.barleyTwist: Nearest neighbour communication only. An IPU may send to only 3 other IPUs, one rung up, one rung down, and to it’s neighbour on the same ladder rung (see
ipuLinkTopology
). This has double the bandwidth available compared to fixedWindow and slidingWindow.
syncConfiguration
(intraReplicaAndAll, ipuAndAll) [=intraReplicaAndAll]The configuration of the hardware synchronisation groups. Note the
target.syncReplicasIndependently
engine option determines which of the synchronisation groups is used for host synchronisation.intraReplicaAndAll: The first sync group is used to sync IPUs within a replica and the second sync group is used to sync all IPUs.
ipuAndAll: The first sync group is used to sync each IPU independently with the host (if the
target.syncReplicasIndependently
option is set) and the second sync group is used to sync all IPUs.
ipuLinkTopology
(mesh, torus) [=mesh]The topology of the IPU-Links. It describes how the IPUs in the system are connected.
mesh: The IPUs are connected as a ladder.
torus: The IPUs are connected as a ladder, with the top and bottom of the ladder linked together.
IpuLinkDomainSize
Integer [=64]The number of IPUs connected via IPU-Links. Two IPU-Link domains can be connected together via GW-Links.
Public Functions
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Target()
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~Target()
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void serialize(std::ostream &out) const
Serialize a target to a stream.
Currently the format is opaque, and compatibility between different versions of Poplar is not guaranteed.
- Parameters
out – The stream to write to.
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TargetType getTargetType() const
The target type.
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unsigned getNumIPUs() const
The number of IPUs.
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unsigned getTilesPerIPU() const
The number of tiles per IPU.
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unsigned getNumWorkerContexts() const
The number of worker contexts per tile.
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unsigned getBytesPerTile() const
Bytes of memory per tile.
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unsigned getExchangeBytesPerCycle() const
The bandwidth of internal IPU exchange in bytes per cycle.
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unsigned getMemcpyBytesPerCycle() const
The maximum bandwidth for internal data copies on a tile.
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unsigned getMinIPUSyncDelay() const
The IPU sync delay for the tile that is closest to the sync controller.
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unsigned getGlobalSyncCycles() const
The number of clock cycles required to synchronize all IPUs.
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unsigned getInterleavedMemoryElementIndex() const
Memory element offset index for interleaved memory.
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const std::vector<GlobalExchangeConstraint> &getGlobalExchangeConstraints() const
Set of constraints that provide a lower bound on the time it takes to send data between IPUs.
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unsigned getNumStrideBits() const
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unsigned getDataPathWidth() const
The width of the load/store data path within the tile.
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unsigned getFp8ConvUnitMaxPipelineDepth() const
The maximum pipeline depth of the convolution units within the tile for fp8.
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unsigned getFp16ConvUnitMaxPipelineDepth() const
The maximum pipeline depth of the convolution units within the tile for fp16.
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unsigned getFp32ConvUnitMaxPipelineDepth() const
The maximum pipeline depth of the convolution units within the tile for fp32.
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unsigned getFp8ConvUnitInputLoadElemsPerCycle() const
The number of input elements loaded per cycle in f8 convolution unit.
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unsigned getFp16ConvUnitInputLoadElemsPerCycle() const
The number of input elements loaded per cycle in f16 convolution unit.
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unsigned getFp32ConvUnitInputLoadElemsPerCycle() const
The number of input elements loaded per cycle in f32 convolution unit.
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unsigned getFp16InFp16OutConvUnitsPerTile() const
The number of convolution units in the tile that can be used when partial results are outputs as 16-bits and inputs are 16 bits.
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unsigned getFp16InFp32OutConvUnitsPerTile() const
The number of convolution units in the tile that can be used when partial results are outputs as 32-bits and inputs are 16 bits.
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unsigned getFp32InFp32OutConvUnitsPerTile() const
The number of convolution units in the tile that can be used when accumulating to 32 bit values.
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unsigned getFp8InFp16OutConvUnitsPerTile() const
The number of convolution units in the tile that can be used when partial results are 16-bits and inputs are 8-bits.
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unsigned getConvUnitCoeffLoadBytesPerCycle() const
The number of convolutional weights that can be loaded in a cycle.
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unsigned getRptCountMax() const
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bool supportsExchangeBusSharing() const
Whether tiles can share the local exchange bus during exchange.
The number of consecutive tiles that can share the exchange bus.
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unsigned getNumTiles() const
Get the total number of tiles for this target (tiles per IPU * number of IPUs).
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std::uint64_t getMemoryBytes() const
Get the total amount of memory on this target, across all IPUs.
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unsigned getFloatVectorWidth() const
How many floats can be processed in one vector operation.
Equivalent to getDataPathWidth() / 32.
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unsigned getHalfVectorWidth() const
How many halves can be processed in one vector operation.
Equivalent to getDataPathWidth() / 16.
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unsigned getQuarterVectorWidth() const
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unsigned getQuarterMetadataVectorWidth() const
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unsigned getVectorWidth(const poplar::Type &type) const
How many of the given type can be processed in one vector operation.
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unsigned getMaxIPUSyncDelay() const
Get the maximum number of cycles required for an IPU sync in the best case scenario (all tiles are immediately ready).
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double getTileClockFrequency() const
Get the tile clock frequency in Hertz.
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unsigned getNumTilesPerXBContext() const
Get the number of tiles per exchange-block context (with repair).
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unsigned getNumContextsPerXB() const
Get the number of contexts per exchange-block.
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unsigned getTileHostExchangeXB(unsigned tile) const
Get the XB of a tile.
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unsigned getTileHostExchangeContext(unsigned tile) const
Get the context of a tile within an XB.
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unsigned getTileHostExchangeContextPosition(unsigned tile) const
Get the position of a tile within a context.
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template<typename T>
T getTypeLimitsMaxAs(const Type&) const = delete Get the maximum representable finite value of a given type.
Template parameter specifies return type.
Base templated method is deleted, see declared specialisations of this method for valid return types.
- Parameters
t – The type.
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template<typename T>
T getTypeLimitsLowestAs(const Type&) const = delete Get the lowest representable finite value of a given type.
Template parameter specifies return type.
Base templated method is deleted, see declared specialisations of this method for valid return types.
- Parameters
t – The type.
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std::size_t getAtomicStoreGranularity() const
Get the granularity of atomic stores that can be made by independent parallel worker threads.
- Returns
The granularity in bytes.
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uint32_t makeFpIctlValue(bool inv, bool div0, bool oflo, bool esr, bool nanoo) const
Generate a value that could be written to Floating Point Initial Control Value register CSR_S.FP_ICTL in order to configure it with the specified options.
- Parameters
inv –
If true, a floating-point invalid operation (defined by IEEE 754) will cause an exception.
The invalid operations are:
Addition or subtraction where the operands are + or - infinity (inf) and the operation results in the subtraction of two infs; for example: (-inf)+(+inf) or (+inf)-(+inf).
Divisions: (+/-0)/(+/-0) and (+/-inf)/(+/-inf).
Multiplications: (+/-0)*(+/-inf) and (+/-inf)*(+/-0).
Remainder: x REM y where y=0 or x=(+/-inf)
Real operations with complex results such as the square root or logarithm of a negative number.
Operations with Not-a-Number as at least one operand.
Comparisons where one of the operands is Not-a-Number.
See also nanoo below.
div – If true a floating point divide by zero operation will cause an exception
oflo – If true a floating point overflow will cause an exception
esr – Enable stochastic rounding
nanoo – Enable Not-a-Number on overflow mode. When enabled half precision calculations that have overflowed will produce a Not-a-Number result, rather than saturating to the half precision max/min value, and the invalid operation (
inv
) flag will be set
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unsigned getFpIctlRegIndex() const
Return the register index of the Floating Point Initial Control Value register CSR_S.FP_ICTL.
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unsigned getDbgDataRegIndex() const
Return the register index of CSR_C.DBG_DATA.
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IpuLinkConfiguration getIpuLinkConfiguration() const
Return the IPU-Link configuration of this target.
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IpuLinkTopology getIpuLinkTopology() const
Return the IPU-Link topology.
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unsigned getIpuLinkDomainSize() const
Return the size of the IPU-Link domain.
That is, the number of IPUs that are connected via IPU-Links.
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unsigned getInstanceSize() const
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bool getGatewayMode() const
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Target createVirtualTarget(unsigned numIPUs, unsigned tilesPerIPU) const
Create a “virtual” target consisting of a subset of the target’s tiles.
This method returns a target object that references the same state as this target but only uses a subset of the target’s tiles.
- Parameters
numIPUs – The number of IPUs the target should be for.
tilesPerIPU – The number of tiles per IPU.
- Returns
The virtual target object.
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template<>
double getTypeLimitsMaxAs(const Type &t) const Get the maximum representable finite value of a given type as a double.
- Parameters
t – The type.
- Throws
poplar_error – if the value is not exactly representable as a double.
-
template<>
double getTypeLimitsLowestAs(const Type &t) const Get the lowest representable finite value of a given type as a double.
- Parameters
t – The type.
- Throws
poplar_error – if the value is not exactly representable as a double.
Public Static Functions
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static Target createCPUTarget(bool accurateHalf = false, unsigned numIPUs = 1)
Create a CPU target.
Create a target for executing a simple graph on the CPU.
This should only be used for simple functional testing.
- Parameters
accurateHalf – By default, half is an alias for float, and
sizeof(half)
will be 4. If you setaccurateHalf
to true, half will be implemented in software as 16-bit IEEE floating point. This will be slower, but will produce the same results as the IPU.numIPUs – The number of IPUs in the target. The IPUs will each have 1 tile with 1 worker thread.
- Returns
A Target object that can be used to create a graph.
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static Target createIPUTarget(StringRef system, const OptionFlags &opts = {})
Create an IPU target.
Create an IPU target with all IPUs for the system based on the given system type.
Valid system types are:
IPU-POD16
IPU-POD64
IPU-POD128
IPU-POD256
IPU-POD4-DA
IPU-POD16-DA
- Parameters
system – The type of the IPU system.
opts – The options passed to the target.
- Returns
A Target object that can be used to create a graph.
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static Target createIPUTarget(unsigned numIPUs, StringRef system, const OptionFlags &opts = {})
Create an IPU target.
Create an IPU target with a specified number of IPUs based on the given system type.
Valid system types are:
IPU-POD16
IPU-POD64
IPU-POD128
IPU-POD256
IPU-POD4-DA
IPU-POD16-DA
- Parameters
numIPUs – The number of IPUs the target should be for.
system – The type of the IPU system.
opts – The options passed to the target.
- Returns
A Target object that can be used to create a graph.
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static Target createIPUTarget(unsigned numIPUs, unsigned tilesPerIPU, StringRef system, const OptionFlags &opts = {})
Create an IPU target with a virtual number of tiles.
Create an IPU target with a specified number of IPUs based on the given system type. In addition, the number of tiles can be restricted to a smaller virtual number of observable tiles.
Valid system types are:
IPU-POD16
IPU-POD64
IPU-POD128
IPU-POD256
IPU-POD4-DA
IPU-POD16-DA
- Parameters
numIPUs – The number of IPUs the target should be for.
tilesPerIPU – The number of tiles per IPU.
system – The type of the IPU system.
opts – The options passed to the target.
- Returns
A Target object that can be used to create a graph.
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static Target createIPUTarget(unsigned numIPUs, StringRef system, const core::TargetOptions &opts)
Create an IPU target.
Create an IPU target with a specified number of IPUs based on the given system type.
- Deprecated:
Use createIPUTarget(unsigned numIPUs, StringRef system, const OptionFlags &opts) instead.
- Parameters
numIPUs – The number of IPUs the target should be for.
system – The type of the IPU system.
opts – The options passed to the target.
- Returns
A Target object that can be used to create a graph.
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static Target createIPUTarget(unsigned numIPUs, unsigned tilesPerIPU, StringRef system, const core::TargetOptions &opts)
Create an IPU target with a virtual number of tiles, and target options.
Create an IPU target with a specified number of IPUs based on the given system type. In addition, the number of tiles can be restricted to a smaller virtual number of observable tiles. This overload also accepts target options that can be obtained from another target.
- Deprecated:
Use createIPUTarget(unsigned numIPUs, unsigned tilesPerIPU, StringRef system, const OptionFlags &opts) instead.
- Parameters
numIPUs – The number of IPUs the target should be for.
tilesPerIPU – The number of tiles per IPU.
system – The type of the IPU system.
opts – The options passed to the target.
- Returns
A Target object that can be used to create a graph.
Private Functions
-
namespace core
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template<>
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namespace std
- template<> Target >