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Add builtins.unique [WIP]

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This cuts ~4.5s from "nix-env -qaP -f `<nixpkgs>` --out-path" and
reduces memory allocations from 7.49 to 7.16 GiB.

Note that builtins.unique requires a less-than comparator function,
which is a change from the 'unique' function in Nixpkgs which uses an
equality function.
This commit is contained in:
Eelco Dolstra 2019-04-12 22:44:42 +02:00
parent bb6e6923f2
commit a3d874175c
1 changed files with 59 additions and 1 deletions
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60
src/libexpr/primops.cc
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@ -341,6 +341,8 @@ struct CompareValues
return strcmp(v1->string.s, v2->string.s) < 0;
case tPath:
return strcmp(v1->path, v2->path) < 0;
case tAttrs:
return v1 < v2; // FIXME
default:
throw EvalError(format("cannot compare %1% with %2%") % showType(*v1) % showType(*v2));
}
@ -1576,7 +1578,6 @@ static void prim_sort(EvalState & state, const Pos & pos, Value * * args, Value
v.listElems()[n] = args[1]->listElems()[n];
}
auto comparator = [&](Value * a, Value * b) {
/* Optimization: if the comparator is lessThan, bypass
callFunction. */
@ -1596,6 +1597,62 @@ static void prim_sort(EvalState & state, const Pos & pos, Value * * args, Value
}
static void prim_unique(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
state.forceFunction(*args[0], pos);
state.forceList(*args[1], pos);
auto len = args[1]->listSize();
Value * vs[len];
for (size_t n = 0; n < len; ++n) {
auto v2 = args[1]->listElems()[n];
state.forceValue(*v2);
vs[n] = v2;
}
auto comparator = [&](Value * a, Value * b) {
/* Optimization: if the comparator is lessThan, bypass
callFunction. */
if (args[0]->type == tPrimOp && args[0]->primOp->fun == prim_lessThan)
return CompareValues()(a, b);
Value vTmp1, vTmp2;
state.callFunction(*args[0], *a, vTmp1, pos);
state.callFunction(vTmp1, *b, vTmp2, pos);
return state.forceBool(vTmp2, pos);
};
std::sort(vs, vs + len, comparator);
auto outLen = std::min((size_t) 1, len);
for (size_t n = 1; n < len; n++) {
if (comparator(vs[outLen - 1], vs[n])) {
vs[outLen++] = vs[n];
}
}
std::sort(vs, vs + outLen);
state.mkList(v, outLen);
size_t outPos = 0;
for (size_t n = 0; n < len; n++) {
auto v2 = args[1]->listElems()[n];
auto i = std::lower_bound(vs, vs + outLen, v2);
if (*i == v2) {
// Remove v2 from the set by setting its least significant
// bit. (This doesn't change the sort order.)
*i = (Value *) (((ptrdiff_t) v2) | 1);
assert(outPos < outLen);
v.listElems()[outPos++] = v2;
}
}
assert(outPos == outLen);
}
static void prim_partition(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
state.forceFunction(*args[0], pos);
@ -2240,6 +2297,7 @@ void EvalState::createBaseEnv()
addPrimOp("__all", 2, prim_all);
addPrimOp("__genList", 2, prim_genList);
addPrimOp("__sort", 2, prim_sort);
addPrimOp("__unique", 2, prim_unique);
addPrimOp("__partition", 2, prim_partition);
addPrimOp("__concatMap", 2, prim_concatMap);