Compiler plugin for implementing incremental computation in user space (#10819)
This plugin provides essential building block for implementing incremental computations in your programs. The idea behind incremental computations is that if you do the same calculation multiple times but with slightly different inputs you don't have to recompute everything from scratch. Also you don't want to adopt special algorithms either, you would like to write your code in standard from scratch manner and get incrementality for free when it is possible. The plugin computes the digest of the proc bodies, recursively hashing all called procs as well . Such digest with the digest of the argument values gives a good "name" for the result. Terminology loosely follows paper "Incremental Computation with Names" link below. It works well if you have no side effects in your computations. If you have global state in your computations then you will need problem specific workarounds to represent global state in set of "names" . SideEffect tracking in Nim also useful in this topic. Classical examples: Dashboard with ticking data. New data arrives non stop and you would like to update the dashboard recomputing only changed outputs. Excel spreadsheet where user changes one cell and you would like to recompute all cells that are affected by the change, but do not want to recompute every cell in the spreadsheet.
This commit is contained in:
cooldome
Andreas Rumpf
parent
de02fd0b89
commit
041d15392a
14 changed files with 387 additions and 82 deletions
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@ -9,81 +9,26 @@
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## Computes hash values for routine (proc, method etc) signatures.
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import ast, md5, tables, ropes
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import ast, tables, ropes, md5, modulegraphs
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from hashes import Hash
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from astalgo import debug
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import types
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from strutils import startsWith, contains
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when false:
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type
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SigHash* = uint32 ## a hash good enough for a filename or a proc signature
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proc `&=`(c: var MD5Context, s: string) = md5Update(c, s, s.len)
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proc `&=`(c: var MD5Context, ch: char) = md5Update(c, unsafeAddr ch, 1)
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proc `&=`(c: var MD5Context, r: Rope) =
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for l in leaves(r): md5Update(c, l, l.len)
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proc `&=`(c: var MD5Context, i: BiggestInt) =
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md5Update(c, cast[cstring](unsafeAddr i), sizeof(i))
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proc `&=`(c: var MD5Context, f: BiggestFloat) =
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md5Update(c, cast[cstring](unsafeAddr f), sizeof(f))
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proc `&=`(c: var MD5Context, s: SigHash) =
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md5Update(c, cast[cstring](unsafeAddr s), sizeof(s))
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template lowlevel(v) =
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md5Update(c, cast[cstring](unsafeAddr(v)), sizeof(v))
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proc sdbmHash(hash: SigHash, c: char): SigHash {.inline.} =
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return SigHash(c) + (hash shl 6) + (hash shl 16) - hash
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template `&=`*(x: var SigHash, c: char) = x = sdbmHash(x, c)
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template `&=`*(x: var SigHash, s: string) =
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for c in s: x = sdbmHash(x, c)
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else:
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type
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SigHash* = distinct Md5Digest
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const
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cb64 = [
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"A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N",
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"O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z",
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"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n",
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"o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z",
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"0", "1", "2", "3", "4", "5", "6", "7", "8", "9a",
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"9b", "9c"]
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proc toBase64a(s: cstring, len: int): string =
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## encodes `s` into base64 representation.
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result = newStringOfCap(((len + 2) div 3) * 4)
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result.add '_'
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var i = 0
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while i < len - 2:
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let a = ord(s[i])
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let b = ord(s[i+1])
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let c = ord(s[i+2])
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result.add cb64[a shr 2]
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result.add cb64[((a and 3) shl 4) or ((b and 0xF0) shr 4)]
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result.add cb64[((b and 0x0F) shl 2) or ((c and 0xC0) shr 6)]
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result.add cb64[c and 0x3F]
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inc(i, 3)
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if i < len-1:
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let a = ord(s[i])
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let b = ord(s[i+1])
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result.add cb64[a shr 2]
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result.add cb64[((a and 3) shl 4) or ((b and 0xF0) shr 4)]
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result.add cb64[((b and 0x0F) shl 2)]
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elif i < len:
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let a = ord(s[i])
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result.add cb64[a shr 2]
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result.add cb64[(a and 3) shl 4]
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proc `$`*(u: SigHash): string =
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toBase64a(cast[cstring](unsafeAddr u), sizeof(u))
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proc `&=`(c: var MD5Context, s: string) = md5Update(c, s, s.len)
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proc `&=`(c: var MD5Context, ch: char) = md5Update(c, unsafeAddr ch, 1)
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proc `&=`(c: var MD5Context, r: Rope) =
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for l in leaves(r): md5Update(c, l, l.len)
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proc `&=`(c: var MD5Context, i: BiggestInt) =
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md5Update(c, cast[cstring](unsafeAddr i), sizeof(i))
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template lowlevel(v) =
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md5Update(c, cast[cstring](unsafeAddr(v)), sizeof(v))
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proc `==`*(a, b: SigHash): bool =
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# {.borrow.}
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result = equalMem(unsafeAddr a, unsafeAddr b, sizeof(a))
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proc hash*(u: SigHash): Hash =
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result = 0
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for x in 0..3:
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result = (result shl 8) or u.MD5Digest[x].int
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type
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ConsiderFlag* = enum
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CoProc
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@ -359,6 +304,75 @@ proc sigHash*(s: PSym): SigHash =
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else:
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result = hashNonProc(s)
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proc symBodyDigest*(graph: ModuleGraph, sym: PSym): SigHash
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proc hashBodyTree(graph: ModuleGraph, c: var MD5Context, n: PNode)
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proc hashVarSymBody(graph: ModuleGraph, c: var MD5Context, s: PSym) =
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assert: s.kind in {skParam, skResult, skVar, skLet, skConst, skForVar}
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if sfGlobal notin s.flags:
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c &= char(s.kind)
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c &= s.name.s
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else:
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c &= hashNonProc(s)
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# this one works for let and const but not for var. True variables can change value
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# later on. it is user resposibility to hash his global state if required
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if s.ast != nil and s.ast.kind == nkIdentDefs:
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hashBodyTree(graph, c, s.ast[^1])
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else:
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hashBodyTree(graph, c, s.ast)
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proc hashBodyTree(graph: ModuleGraph, c: var MD5Context, n: PNode) =
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# hash Nim tree recursing into simply
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if n == nil:
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c &= "nil"
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return
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c &= char(n.kind)
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case n.kind
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of nkEmpty, nkNilLit, nkType: discard
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of nkIdent:
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c &= n.ident.s
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of nkSym:
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if n.sym.kind in skProcKinds:
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c &= symBodyDigest(graph, n.sym)
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elif n.sym.kind in {skParam, skResult, skVar, skLet, skConst, skForVar}:
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hashVarSymBody(graph, c, n.sym)
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else:
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c &= hashNonProc(n.sym)
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of nkProcDef, nkFuncDef, nkTemplateDef, nkMacroDef:
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discard # we track usage of proc symbols not their definition
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of nkCharLit..nkUInt64Lit:
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c &= n.intVal
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of nkFloatLit..nkFloat64Lit:
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c &= n.floatVal
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of nkStrLit..nkTripleStrLit:
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c &= n.strVal
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else:
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for i in 0..<n.len:
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hashTree(c, n.sons[i])
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proc symBodyDigest*(graph: ModuleGraph, sym: PSym): SigHash =
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## compute unique digest of the proc/func/method symbols
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## recursing into invoked symbols as well
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assert(sym.kind in skProcKinds, $sym.kind)
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graph.symBodyHashes.withValue(sym.id, value):
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return value[]
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var c: MD5Context
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md5Init(c)
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c.hashType(sym.typ, {CoProc})
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c &= char(sym.kind)
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c.md5Final(result.Md5Digest)
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graph.symBodyHashes[sym.id] = result # protect from recursion in the body
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if sym.ast != nil:
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md5Init(c)
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c.md5Update(cast[cstring](result.addr), sizeof(result))
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c.hashTree(sym.ast[bodyPos])
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c.md5Final(result.Md5Digest)
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graph.symBodyHashes[sym.id] = result
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proc idOrSig*(s: PSym, currentModule: string,
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sigCollisions: var CountTable[SigHash]): Rope =
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if s.kind in routineKinds and s.typ != nil:
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