| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Futhark.Representation.ExplicitMemory
Description
This representation requires that every array is given information about which memory block is it based in, and how array elements map to memory block offsets. The representation is based on the kernels representation, so nested parallelism does not occur.
There are two primary concepts you will need to understand:
- Memory blocks, which are Futhark values of type
Mem(parametrized with their size). These correspond to arbitrary blocks of memory, and are created using theAllocoperation. - Index functions, which describe a mapping from the index space
of an array (eg. a two-dimensional space for an array of type
[[int]]) to a one-dimensional offset into a memory block. Thus, index functions describe how arbitrary-dimensional arrays are mapped to the single-dimensional world of memory.
At a conceptual level, imagine that we have a two-dimensional array
a of 32-bit integers, consisting of n rows of m elements
each. This array could be represented in classic row-major format
with an index function like the following:
f(i,j) = i * m + j
When we want to know the location of element a[2,3], we simply
call the index function as f(2,3) and obtain 2*m+3. We could
also have chosen another index function, one that represents the
array in column-major (or "transposed") format:
f(i,j) = j * n + i
Index functions are not Futhark-level functions, but a special construct that the final code generator will eventually use to generate concrete access code. By modifying the index functions we can change how an array is represented in memory, which can permit memory access pattern optimisations.
Every time we bind an array, whether in a let-binding, loop
merge parameter, or lambda parameter, we have an annotation
specifying a memory block and an index function. In some cases,
such as let-bindings for many expressions, we are free to specify
an arbitrary index function and memory block - for example, we get
to decide where Copy stores its result - but in other cases the
type rules of the expression chooses for us. For example, Index
always produces an array in the same memory block as its input, and
with the same index function, except with some indices fixed.
Synopsis
- data ExplicitMemory
- data InKernel
- data MemOp inner
- data MemInfo d u ret
- type MemBound u = MemInfo SubExp u MemBind
- data MemBind = ArrayIn VName IxFun
- data MemReturn
- type IxFun = IxFun (PrimExp VName)
- type ExtIxFun = IxFun (PrimExp (Ext VName))
- isStaticIxFun :: ExtIxFun -> Maybe IxFun
- type ExpReturns = MemInfo ExtSize NoUniqueness (Maybe MemReturn)
- type BodyReturns = MemInfo ExtSize NoUniqueness MemReturn
- type FunReturns = MemInfo ExtSize Uniqueness MemReturn
- noUniquenessReturns :: MemInfo d u r -> MemInfo d NoUniqueness r
- bodyReturnsToExpReturns :: BodyReturns -> ExpReturns
- type ExplicitMemorish lore = (SameScope lore ExplicitMemory, RetType lore ~ FunReturns, BranchType lore ~ BodyReturns, CanBeAliased (Op lore), Attributes lore, Annotations lore, Checkable lore, OpReturns lore)
- expReturns :: (Monad m, HasScope lore m, ExplicitMemorish lore) => Exp lore -> m [ExpReturns]
- extReturns :: [ExtType] -> [ExpReturns]
- sliceInfo :: (Monad m, HasScope lore m, ExplicitMemorish lore) => VName -> Slice SubExp -> m (MemInfo SubExp NoUniqueness MemBind)
- lookupMemInfo :: (HasScope lore m, ExplicitMemorish lore) => VName -> m (MemInfo SubExp NoUniqueness MemBind)
- subExpMemInfo :: (HasScope lore m, Monad m, ExplicitMemorish lore) => SubExp -> m (MemInfo SubExp NoUniqueness MemBind)
- lookupMemSize :: (HasScope lore m, Monad m) => VName -> m SubExp
- lookupArraySummary :: (ExplicitMemorish lore, HasScope lore m, Monad m) => VName -> m (VName, IxFun (PrimExp VName))
- fullyLinear :: (Eq num, IntegralExp num) => ShapeBase num -> IxFun num -> Bool
- ixFunMatchesInnerShape :: (Eq num, IntegralExp num) => ShapeBase num -> IxFun num -> Bool
- existentialiseIxFun :: [VName] -> IxFun -> ExtIxFun
- module Futhark.Representation.AST.Attributes
- module Futhark.Representation.AST.Traversals
- module Futhark.Representation.AST.Pretty
- module Futhark.Representation.AST.Syntax
- module Futhark.Representation.Kernels.Kernel
- module Futhark.Representation.Kernels.KernelExp
- module Futhark.Analysis.PrimExp.Convert
The Lore definition
data ExplicitMemory Source #
A lore containing explicit memory information.
Instances
Instances
Constructors
| Alloc SubExp Space | Allocate a memory block. This really should not be an expression, but what are you gonna do... |
| Inner inner |
Instances
A summary of the memory information for every let-bound identifier, function parameter, and return value. Parameterisered over uniqueness, dimension, and auxiliary array information.
Constructors
| MemPrim PrimType | A primitive value. |
| MemMem d Space | A memory block. |
| MemArray PrimType (ShapeBase d) u ret | The array is stored in the named memory block, and with the given index function. The index function maps indices in the array to element offset, not byte offsets! To translate to byte offsets, multiply the offset with the size of the array element type. |
Instances
Memory information for an array bound somewhere in the program.
Instances
A description of the memory properties of an array being returned by an operation.
Constructors
| ReturnsInBlock VName ExtIxFun | The array is located in a memory block that is already in scope. |
| ReturnsNewBlock Space Int ExtSize ExtIxFun | The operation returns a new (existential) block, with an existential or known size. |
Instances
| Eq MemReturn Source # | |
| Ord MemReturn Source # | |
Defined in Futhark.Representation.ExplicitMemory | |
| Show MemReturn Source # | |
| Pretty MemReturn Source # | |
| FixExt MemReturn Source # | |
| IsRetType FunReturns Source # | |
Defined in Futhark.Representation.ExplicitMemory Methods primRetType :: PrimType -> FunReturns Source # applyRetType :: Typed attr => [FunReturns] -> [Param attr] -> [(SubExp, Type)] -> Maybe [FunReturns] Source # | |
| IsBodyType BodyReturns Source # | |
Defined in Futhark.Representation.ExplicitMemory Methods primBodyType :: PrimType -> BodyReturns Source # | |
| FreeIn MemReturn Source # | |
| Substitute MemReturn Source # | |
Defined in Futhark.Representation.ExplicitMemory | |
| Rename MemReturn Source # | |
| Simplifiable MemReturn Source # | |
Defined in Futhark.Representation.ExplicitMemory | |
| Simplifiable [FunReturns] Source # | |
Defined in Futhark.Representation.ExplicitMemory Methods simplify :: SimplifiableLore lore => [FunReturns] -> SimpleM lore [FunReturns] Source # | |
type IxFun = IxFun (PrimExp VName) Source #
The index function representation used for memory annotations.
type ExtIxFun = IxFun (PrimExp (Ext VName)) Source #
An index function that may contain existential variables.
type ExpReturns = MemInfo ExtSize NoUniqueness (Maybe MemReturn) Source #
The memory return of an expression. An array is annotated with
Maybe MemReturn, which can be interpreted as the expression
either dictating exactly where the array is located when it is
returned (if Just), or able to put it whereever the binding
prefers (if Nothing).
This is necessary to capture the difference between an expression
that is just an array-typed variable, in which the array being
"returned" is located where it already is, and a copy expression,
whose entire purpose is to store an existing array in some
arbitrary location. This is a consequence of the design decision
never to have implicit memory copies.
type BodyReturns = MemInfo ExtSize NoUniqueness MemReturn Source #
The return of a body, which must always indicate where returned arrays are located.
type FunReturns = MemInfo ExtSize Uniqueness MemReturn Source #
The memory return of a function, which must always indicate where returned arrays are located.
noUniquenessReturns :: MemInfo d u r -> MemInfo d NoUniqueness r Source #
type ExplicitMemorish lore = (SameScope lore ExplicitMemory, RetType lore ~ FunReturns, BranchType lore ~ BodyReturns, CanBeAliased (Op lore), Attributes lore, Annotations lore, Checkable lore, OpReturns lore) Source #
expReturns :: (Monad m, HasScope lore m, ExplicitMemorish lore) => Exp lore -> m [ExpReturns] Source #
The return information of an expression. This can be seen as the "return type with memory annotations" of the expression.
extReturns :: [ExtType] -> [ExpReturns] Source #
sliceInfo :: (Monad m, HasScope lore m, ExplicitMemorish lore) => VName -> Slice SubExp -> m (MemInfo SubExp NoUniqueness MemBind) Source #
lookupMemInfo :: (HasScope lore m, ExplicitMemorish lore) => VName -> m (MemInfo SubExp NoUniqueness MemBind) Source #
subExpMemInfo :: (HasScope lore m, Monad m, ExplicitMemorish lore) => SubExp -> m (MemInfo SubExp NoUniqueness MemBind) Source #
lookupArraySummary :: (ExplicitMemorish lore, HasScope lore m, Monad m) => VName -> m (VName, IxFun (PrimExp VName)) Source #
fullyLinear :: (Eq num, IntegralExp num) => ShapeBase num -> IxFun num -> Bool Source #
Is an array of the given shape stored fully flat row-major with the given index function?
ixFunMatchesInnerShape :: (Eq num, IntegralExp num) => ShapeBase num -> IxFun num -> Bool Source #