d70bbfb5d0
The simple type unification algorithm suffered from some serious performance and memory problems when used with certain code bases. This adds some crucial optimizations that improve performance drastically.
643 lines
21 KiB
Go
643 lines
21 KiB
Go
// Mgmt
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// Copyright (C) 2013-2019+ James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package unification // TODO: can we put this solver in a sub-package?
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import (
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"fmt"
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"github.com/purpleidea/mgmt/lang/interfaces"
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"github.com/purpleidea/mgmt/lang/types"
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"github.com/purpleidea/mgmt/util/errwrap"
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)
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const (
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// Name is the prefix for our solver log messages.
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Name = "solver: simple"
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)
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// SimpleInvariantSolverLogger is a wrapper which returns a
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// SimpleInvariantSolver with the log parameter of your choice specified. The
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// result satisfies the correct signature for the solver parameter of the
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// Unification function.
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func SimpleInvariantSolverLogger(logf func(format string, v ...interface{})) func([]interfaces.Invariant, []interfaces.Expr) (*InvariantSolution, error) {
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return func(invariants []interfaces.Invariant, expected []interfaces.Expr) (*InvariantSolution, error) {
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return SimpleInvariantSolver(invariants, expected, logf)
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}
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}
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// SimpleInvariantSolver is an iterative invariant solver for AST expressions.
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// It is intended to be very simple, even if it's computationally inefficient.
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func SimpleInvariantSolver(invariants []interfaces.Invariant, expected []interfaces.Expr, logf func(format string, v ...interface{})) (*InvariantSolution, error) {
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debug := false // XXX: add to interface
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logf("%s: invariants:", Name)
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for i, x := range invariants {
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logf("invariant(%d): %T: %s", i, x, x)
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}
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solved := make(map[interfaces.Expr]*types.Type)
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equalities := []interfaces.Invariant{}
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exclusives := []*ExclusiveInvariant{}
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// iterate through all invariants, flattening and sorting the list...
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for _, x := range invariants {
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switch invariant := x.(type) {
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case *EqualsInvariant:
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equalities = append(equalities, invariant)
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case *EqualityInvariant:
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equalities = append(equalities, invariant)
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case *EqualityInvariantList:
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// de-construct this list variant into a series
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// of equality variants so that our solver can
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// be implemented more simply...
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if len(invariant.Exprs) < 2 {
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return nil, fmt.Errorf("list invariant needs at least two elements")
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}
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for i := 0; i < len(invariant.Exprs)-1; i++ {
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invar := &EqualityInvariant{
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Expr1: invariant.Exprs[i],
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Expr2: invariant.Exprs[i+1],
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}
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equalities = append(equalities, invar)
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}
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case *EqualityWrapListInvariant:
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equalities = append(equalities, invariant)
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case *EqualityWrapMapInvariant:
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equalities = append(equalities, invariant)
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case *EqualityWrapStructInvariant:
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equalities = append(equalities, invariant)
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case *EqualityWrapFuncInvariant:
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equalities = append(equalities, invariant)
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// contains a list of invariants which this represents
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case *ConjunctionInvariant:
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for _, invar := range invariant.Invariants {
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equalities = append(equalities, invar)
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}
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case *ExclusiveInvariant:
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// these are special, note the different list
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if len(invariant.Invariants) > 0 {
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exclusives = append(exclusives, invariant)
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}
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case *AnyInvariant:
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equalities = append(equalities, invariant)
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default:
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return nil, fmt.Errorf("unknown invariant type: %T", x)
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}
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}
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listPartials := make(map[interfaces.Expr]map[interfaces.Expr]*types.Type)
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mapPartials := make(map[interfaces.Expr]map[interfaces.Expr]*types.Type)
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structPartials := make(map[interfaces.Expr]map[interfaces.Expr]*types.Type)
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funcPartials := make(map[interfaces.Expr]map[interfaces.Expr]*types.Type)
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isSolved := func(solved map[interfaces.Expr]*types.Type) bool {
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for _, x := range expected {
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if typ, exists := solved[x]; !exists || typ == nil {
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return false
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}
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}
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return true
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}
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logf("%s: starting loop with %d equalities", Name, len(equalities))
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// run until we're solved, stop consuming equalities, or type clash
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Loop:
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for {
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logf("%s: iterate...", Name)
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if len(equalities) == 0 && len(exclusives) == 0 {
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break // we're done, nothing left
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}
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used := []int{}
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for i, x := range equalities {
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logf("%s: match(%T): %+v", Name, x, x)
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// TODO: could each of these cases be implemented as a
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// method on the Invariant type to simplify this code?
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switch eq := x.(type) {
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// trivials
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case *EqualsInvariant:
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typ, exists := solved[eq.Expr]
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if !exists {
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solved[eq.Expr] = eq.Type // yay, we learned something!
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used = append(used, i) // mark equality as used up
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logf("%s: solved trivial equality", Name)
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continue
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}
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// we already specified this, so check the repeat is consistent
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if err := typ.Cmp(eq.Type); err != nil {
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// this error shouldn't happen unless we purposefully
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// try to trick the solver, or we're in a recursive try
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with equals")
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}
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used = append(used, i) // mark equality as duplicate
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logf("%s: duplicate trivial equality", Name)
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continue
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// partials
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case *EqualityWrapListInvariant:
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if _, exists := listPartials[eq.Expr1]; !exists {
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listPartials[eq.Expr1] = make(map[interfaces.Expr]*types.Type)
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}
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if typ, exists := solved[eq.Expr1]; exists {
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// wow, now known, so tell the partials!
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// TODO: this assumes typ is a list, is that guaranteed?
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listPartials[eq.Expr1][eq.Expr2Val] = typ.Val
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}
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// can we add to partials ?
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for _, y := range []interfaces.Expr{eq.Expr2Val} {
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typ, exists := solved[y]
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if !exists {
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continue
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}
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t, exists := listPartials[eq.Expr1][y]
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if !exists {
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listPartials[eq.Expr1][y] = typ // learn!
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continue
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}
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if err := t.Cmp(typ); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with partial list val")
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}
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}
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// can we solve anything?
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var ready = true // assume ready
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typ := &types.Type{
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Kind: types.KindList,
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}
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valTyp, exists := listPartials[eq.Expr1][eq.Expr2Val]
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if !exists {
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ready = false // nope!
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} else {
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typ.Val = valTyp // build up typ
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}
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if ready {
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if t, exists := solved[eq.Expr1]; exists {
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if err := t.Cmp(typ); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with list")
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}
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}
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// sub checks
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if t, exists := solved[eq.Expr2Val]; exists {
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if err := t.Cmp(typ.Val); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with list val")
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}
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}
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solved[eq.Expr1] = typ // yay, we learned something!
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solved[eq.Expr2Val] = typ.Val // yay, we learned something!
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used = append(used, i) // mark equality as used up
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logf("%s: solved list wrap partial", Name)
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continue
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}
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case *EqualityWrapMapInvariant:
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if _, exists := mapPartials[eq.Expr1]; !exists {
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mapPartials[eq.Expr1] = make(map[interfaces.Expr]*types.Type)
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}
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if typ, exists := solved[eq.Expr1]; exists {
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// wow, now known, so tell the partials!
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// TODO: this assumes typ is a map, is that guaranteed?
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mapPartials[eq.Expr1][eq.Expr2Key] = typ.Key
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mapPartials[eq.Expr1][eq.Expr2Val] = typ.Val
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}
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// can we add to partials ?
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for _, y := range []interfaces.Expr{eq.Expr2Key, eq.Expr2Val} {
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typ, exists := solved[y]
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if !exists {
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continue
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}
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t, exists := mapPartials[eq.Expr1][y]
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if !exists {
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mapPartials[eq.Expr1][y] = typ // learn!
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continue
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}
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if err := t.Cmp(typ); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with partial map key/val")
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}
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}
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// can we solve anything?
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var ready = true // assume ready
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typ := &types.Type{
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Kind: types.KindMap,
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}
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keyTyp, exists := mapPartials[eq.Expr1][eq.Expr2Key]
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if !exists {
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ready = false // nope!
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} else {
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typ.Key = keyTyp // build up typ
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}
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valTyp, exists := mapPartials[eq.Expr1][eq.Expr2Val]
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if !exists {
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ready = false // nope!
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} else {
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typ.Val = valTyp // build up typ
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}
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if ready {
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if t, exists := solved[eq.Expr1]; exists {
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if err := t.Cmp(typ); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with map")
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}
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}
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// sub checks
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if t, exists := solved[eq.Expr2Key]; exists {
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if err := t.Cmp(typ.Key); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with map key")
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}
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}
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if t, exists := solved[eq.Expr2Val]; exists {
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if err := t.Cmp(typ.Val); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with map val")
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}
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}
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solved[eq.Expr1] = typ // yay, we learned something!
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solved[eq.Expr2Key] = typ.Key // yay, we learned something!
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solved[eq.Expr2Val] = typ.Val // yay, we learned something!
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used = append(used, i) // mark equality as used up
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logf("%s: solved map wrap partial", Name)
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continue
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}
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case *EqualityWrapStructInvariant:
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if _, exists := structPartials[eq.Expr1]; !exists {
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structPartials[eq.Expr1] = make(map[interfaces.Expr]*types.Type)
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}
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if typ, exists := solved[eq.Expr1]; exists {
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// wow, now known, so tell the partials!
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// TODO: this assumes typ is a struct, is that guaranteed?
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if len(typ.Ord) != len(eq.Expr2Ord) {
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return nil, fmt.Errorf("struct field count differs")
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}
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for i, name := range eq.Expr2Ord {
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expr := eq.Expr2Map[name] // assume key exists
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structPartials[eq.Expr1][expr] = typ.Map[typ.Ord[i]] // assume key exists
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}
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}
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// can we add to partials ?
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for name, y := range eq.Expr2Map {
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typ, exists := solved[y]
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if !exists {
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continue
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}
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t, exists := structPartials[eq.Expr1][y]
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if !exists {
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structPartials[eq.Expr1][y] = typ // learn!
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continue
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}
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if err := t.Cmp(typ); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with partial struct field: %s", name)
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}
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}
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// can we solve anything?
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var ready = true // assume ready
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typ := &types.Type{
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Kind: types.KindStruct,
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}
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typ.Map = make(map[string]*types.Type)
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for name, y := range eq.Expr2Map {
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t, exists := structPartials[eq.Expr1][y]
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if !exists {
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ready = false // nope!
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break
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}
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typ.Map[name] = t // build up typ
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}
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if ready {
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typ.Ord = eq.Expr2Ord // known order
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if t, exists := solved[eq.Expr1]; exists {
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if err := t.Cmp(typ); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with struct")
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}
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}
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// sub checks
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for name, y := range eq.Expr2Map {
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if t, exists := solved[y]; exists {
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if err := t.Cmp(typ.Map[name]); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with struct field: %s", name)
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}
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}
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}
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solved[eq.Expr1] = typ // yay, we learned something!
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// we should add the other expr's in too...
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for name, y := range eq.Expr2Map {
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solved[y] = typ.Map[name] // yay, we learned something!
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}
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used = append(used, i) // mark equality as used up
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logf("%s: solved struct wrap partial", Name)
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continue
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}
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case *EqualityWrapFuncInvariant:
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if _, exists := funcPartials[eq.Expr1]; !exists {
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funcPartials[eq.Expr1] = make(map[interfaces.Expr]*types.Type)
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}
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if typ, exists := solved[eq.Expr1]; exists {
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// wow, now known, so tell the partials!
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// TODO: this assumes typ is a func, is that guaranteed?
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if len(typ.Ord) != len(eq.Expr2Ord) {
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return nil, fmt.Errorf("func arg count differs")
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}
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for i, name := range eq.Expr2Ord {
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expr := eq.Expr2Map[name] // assume key exists
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funcPartials[eq.Expr1][expr] = typ.Map[typ.Ord[i]] // assume key exists
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}
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funcPartials[eq.Expr1][eq.Expr2Out] = typ.Out
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}
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// can we add to partials ?
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for name, y := range eq.Expr2Map {
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typ, exists := solved[y]
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if !exists {
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continue
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}
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t, exists := funcPartials[eq.Expr1][y]
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if !exists {
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funcPartials[eq.Expr1][y] = typ // learn!
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continue
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}
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if err := t.Cmp(typ); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with partial func arg: %s", name)
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}
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}
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for _, y := range []interfaces.Expr{eq.Expr2Out} {
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typ, exists := solved[y]
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if !exists {
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continue
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}
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t, exists := funcPartials[eq.Expr1][y]
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if !exists {
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funcPartials[eq.Expr1][y] = typ // learn!
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continue
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}
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if err := t.Cmp(typ); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with partial func arg")
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}
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}
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// can we solve anything?
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var ready = true // assume ready
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typ := &types.Type{
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Kind: types.KindFunc,
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}
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typ.Map = make(map[string]*types.Type)
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for name, y := range eq.Expr2Map {
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t, exists := funcPartials[eq.Expr1][y]
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if !exists {
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ready = false // nope!
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break
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}
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typ.Map[name] = t // build up typ
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}
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outTyp, exists := funcPartials[eq.Expr1][eq.Expr2Out]
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if !exists {
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ready = false // nope!
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} else {
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typ.Out = outTyp // build up typ
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}
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if ready {
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typ.Ord = eq.Expr2Ord // known order
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if t, exists := solved[eq.Expr1]; exists {
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if err := t.Cmp(typ); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with func")
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}
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}
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// sub checks
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for name, y := range eq.Expr2Map {
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if t, exists := solved[y]; exists {
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if err := t.Cmp(typ.Map[name]); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with func arg: %s", name)
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}
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}
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}
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if t, exists := solved[eq.Expr2Out]; exists {
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if err := t.Cmp(typ.Out); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with func out")
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}
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}
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solved[eq.Expr1] = typ // yay, we learned something!
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// we should add the other expr's in too...
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for name, y := range eq.Expr2Map {
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solved[y] = typ.Map[name] // yay, we learned something!
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}
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solved[eq.Expr2Out] = typ.Out // yay, we learned something!
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used = append(used, i) // mark equality as used up
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logf("%s: solved func wrap partial", Name)
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continue
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}
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// regular matching
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case *EqualityInvariant:
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typ1, exists1 := solved[eq.Expr1]
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typ2, exists2 := solved[eq.Expr2]
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if !exists1 && !exists2 { // neither equality connects
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// can't learn more from this equality yet
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// nothing is known about either side of it
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continue
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}
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if exists1 && exists2 { // both equalities already connect
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// both sides are already known-- are they the same?
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if err := typ1.Cmp(typ2); err != nil {
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return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with equality")
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}
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used = append(used, i) // mark equality as used up
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logf("%s: duplicate regular equality", Name)
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continue
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}
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if exists1 && !exists2 { // first equality already connects
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solved[eq.Expr2] = typ1 // yay, we learned something!
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used = append(used, i) // mark equality as used up
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logf("%s: solved regular equality", Name)
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continue
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}
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if exists2 && !exists1 { // second equality already connects
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solved[eq.Expr1] = typ2 // yay, we learned something!
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used = append(used, i) // mark equality as used up
|
|
logf("%s: solved regular equality", Name)
|
|
continue
|
|
}
|
|
|
|
panic("reached unexpected code")
|
|
|
|
// wtf matching
|
|
case *AnyInvariant:
|
|
// this basically ensures that the expr gets solved
|
|
if _, exists := solved[eq.Expr]; exists {
|
|
used = append(used, i) // mark equality as used up
|
|
logf("%s: solved `any` equality", Name)
|
|
}
|
|
continue
|
|
|
|
default:
|
|
return nil, fmt.Errorf("unknown invariant type: %T", x)
|
|
}
|
|
} // end inner for loop
|
|
if len(used) == 0 {
|
|
// Looks like we're now ambiguous, but if we have any
|
|
// exclusives, recurse into each possibility to see if
|
|
// one of them can help solve this! first one wins. Add
|
|
// in the exclusive to the current set of equalities!
|
|
|
|
// To decrease the problem space, first check if we have
|
|
// enough solutions to solve everything. If so, then we
|
|
// don't need to solve any exclusives, and instead we
|
|
// only need to verify that they don't conflict with the
|
|
// found solution, which reduces the search space...
|
|
|
|
// Another optimization that can be done before we run
|
|
// the combinatorial exclusive solver, is we can look at
|
|
// each exclusive, and remove the ones that already
|
|
// match, because they don't tell us any new information
|
|
// that we don't already know. We can also fail early
|
|
// if anything proves we're already inconsistent.
|
|
|
|
// These two optimizations turn out to use the exact
|
|
// same algorithm and code, so they're combined here...
|
|
if isSolved(solved) {
|
|
logf("%s: solved early with %d exclusives left!", Name, len(exclusives))
|
|
} else {
|
|
logf("%s: unsolved with %d exclusives left!", Name, len(exclusives))
|
|
}
|
|
// check for consistency against remaining invariants
|
|
done := []int{}
|
|
for i, invar := range exclusives {
|
|
// test each one to see if at least one works
|
|
match, err := invar.Matches(solved)
|
|
if err != nil {
|
|
if debug {
|
|
logf("exclusive invar failed: %+v", invar)
|
|
}
|
|
return nil, errwrap.Wrapf(err, "inconsistent exclusive")
|
|
}
|
|
if !match {
|
|
continue
|
|
}
|
|
done = append(done, i)
|
|
}
|
|
|
|
// remove exclusives that matched correctly
|
|
for i := len(done) - 1; i >= 0; i-- {
|
|
ix := done[i] // delete index that was marked as done!
|
|
exclusives = append(exclusives[:ix], exclusives[ix+1:]...)
|
|
}
|
|
|
|
if len(exclusives) == 0 {
|
|
break Loop
|
|
}
|
|
|
|
// TODO: Lastly, we could loop through each exclusive
|
|
// and see if it only has a single, easy solution. For
|
|
// example, if we know that an exclusive is A or B or C
|
|
// and that B and C are inconsistent, then we can
|
|
// replace the exclusive with a single invariant and
|
|
// then run that through our solver. We can do this
|
|
// iteratively (recursively in our case) so that if
|
|
// we're lucky, we rarely need to run the raw exclusive
|
|
// combinatorial solver which is slow.
|
|
|
|
// TODO: We could try and replace our combinatorial
|
|
// exclusive solver with a real SAT solver algorithm.
|
|
|
|
// what have we learned for sure so far?
|
|
partialSolutions := []interfaces.Invariant{}
|
|
logf("%s: %d solved, %d unsolved, and %d exclusives left", Name, len(solved), len(equalities), len(exclusives))
|
|
if len(exclusives) > 0 {
|
|
// FIXME: can we do this loop in a deterministic, sorted way?
|
|
for expr, typ := range solved {
|
|
invar := &EqualsInvariant{
|
|
Expr: expr,
|
|
Type: typ,
|
|
}
|
|
partialSolutions = append(partialSolutions, invar)
|
|
logf("%s: solved: %+v", Name, invar)
|
|
}
|
|
|
|
// also include anything that hasn't been solved yet
|
|
for _, x := range equalities {
|
|
partialSolutions = append(partialSolutions, x)
|
|
logf("%s: unsolved: %+v", Name, x)
|
|
}
|
|
}
|
|
|
|
// let's try each combination, one at a time...
|
|
for i, ex := range exclusivesProduct(exclusives) { // [][]interfaces.Invariant
|
|
logf("%s: exclusive(%d):\n%+v", Name, i, ex)
|
|
// we could waste a lot of cpu, and start from
|
|
// the beginning, but instead we could use the
|
|
// list of known solutions found and continue!
|
|
// TODO: make sure none of these edit partialSolutions
|
|
recursiveInvariants := []interfaces.Invariant{}
|
|
recursiveInvariants = append(recursiveInvariants, partialSolutions...)
|
|
recursiveInvariants = append(recursiveInvariants, ex...)
|
|
logf("%s: recursing...", Name)
|
|
solution, err := SimpleInvariantSolver(recursiveInvariants, expected, logf)
|
|
if err != nil {
|
|
logf("%s: recursive solution failed: %+v", Name, err)
|
|
continue // no solution found here...
|
|
}
|
|
// solution found!
|
|
logf("%s: recursive solution found!", Name)
|
|
return solution, nil
|
|
}
|
|
|
|
// TODO: print ambiguity
|
|
return nil, fmt.Errorf("can't unify, no equalities were consumed, we're ambiguous")
|
|
}
|
|
// delete used equalities, in reverse order to preserve indexing!
|
|
for i := len(used) - 1; i >= 0; i-- {
|
|
ix := used[i] // delete index that was marked as used!
|
|
equalities = append(equalities[:ix], equalities[ix+1:]...)
|
|
}
|
|
} // end giant for loop
|
|
|
|
// build final solution
|
|
solutions := []*EqualsInvariant{}
|
|
// FIXME: can we do this loop in a deterministic, sorted way?
|
|
for expr, typ := range solved {
|
|
invar := &EqualsInvariant{
|
|
Expr: expr,
|
|
Type: typ,
|
|
}
|
|
solutions = append(solutions, invar)
|
|
}
|
|
return &InvariantSolution{
|
|
Solutions: solutions,
|
|
}, nil
|
|
}
|