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simplesolver.go
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simplesolver.go
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// Mgmt
// Copyright (C) 2013-2021+ James Shubin and the project contributors
// Written by James Shubin <james@shubin.ca> and the project contributors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package unification // TODO: can we put this solver in a sub-package?
import (
"fmt"
"github.com/purpleidea/mgmt/lang/interfaces"
"github.com/purpleidea/mgmt/lang/types"
"github.com/purpleidea/mgmt/util/errwrap"
)
const (
// Name is the prefix for our solver log messages.
Name = "solver: simple"
// ErrAmbiguous means we couldn't find a solution, but we weren't
// inconsistent.
ErrAmbiguous = interfaces.Error("can't unify, no equalities were consumed, we're ambiguous")
// AllowRecursion specifies whether we're allowed to use the recursive
// solver or not. It uses an absurd amount of memory, and might hang
// your system if a simple solution doesn't exist.
AllowRecursion = false
// RecursionDepthLimit specifies the max depth that is allowed.
// FIXME: RecursionDepthLimit is not currently implemented
RecursionDepthLimit = 5 // TODO: pick a better value ?
// RecursionInvariantLimit specifies the max number of invariants we can
// recurse into.
RecursionInvariantLimit = 5 // TODO: pick a better value ?
)
// SimpleInvariantSolverLogger is a wrapper which returns a
// SimpleInvariantSolver with the log parameter of your choice specified. The
// result satisfies the correct signature for the solver parameter of the
// Unification function.
func SimpleInvariantSolverLogger(logf func(format string, v ...interface{})) func([]interfaces.Invariant, []interfaces.Expr) (*InvariantSolution, error) {
return func(invariants []interfaces.Invariant, expected []interfaces.Expr) (*InvariantSolution, error) {
return SimpleInvariantSolver(invariants, expected, logf)
}
}
// SimpleInvariantSolver is an iterative invariant solver for AST expressions.
// It is intended to be very simple, even if it's computationally inefficient.
func SimpleInvariantSolver(invariants []interfaces.Invariant, expected []interfaces.Expr, logf func(format string, v ...interface{})) (*InvariantSolution, error) {
debug := false // XXX: add to interface
process := func(invariants []interfaces.Invariant) ([]interfaces.Invariant, []*interfaces.ExclusiveInvariant, error) {
equalities := []interfaces.Invariant{}
exclusives := []*interfaces.ExclusiveInvariant{}
generators := []interfaces.Invariant{}
for ix := 0; len(invariants) > ix; ix++ { // while
x := invariants[ix]
switch invariant := x.(type) {
case *interfaces.EqualsInvariant:
equalities = append(equalities, invariant)
case *interfaces.EqualityInvariant:
equalities = append(equalities, invariant)
case *interfaces.EqualityInvariantList:
// de-construct this list variant into a series
// of equality variants so that our solver can
// be implemented more simply...
if len(invariant.Exprs) < 2 {
return nil, nil, fmt.Errorf("list invariant needs at least two elements")
}
for i := 0; i < len(invariant.Exprs)-1; i++ {
invar := &interfaces.EqualityInvariant{
Expr1: invariant.Exprs[i],
Expr2: invariant.Exprs[i+1],
}
equalities = append(equalities, invar)
}
case *interfaces.EqualityWrapListInvariant:
equalities = append(equalities, invariant)
case *interfaces.EqualityWrapMapInvariant:
equalities = append(equalities, invariant)
case *interfaces.EqualityWrapStructInvariant:
equalities = append(equalities, invariant)
case *interfaces.EqualityWrapFuncInvariant:
equalities = append(equalities, invariant)
case *interfaces.EqualityWrapCallInvariant:
equalities = append(equalities, invariant)
case *interfaces.GeneratorInvariant:
// these are special, note the different list
generators = append(generators, invariant)
// contains a list of invariants which this represents
case *interfaces.ConjunctionInvariant:
invariants = append(invariants, invariant.Invariants...)
case *interfaces.ExclusiveInvariant:
// these are special, note the different list
if len(invariant.Invariants) > 0 {
exclusives = append(exclusives, invariant)
}
case *interfaces.AnyInvariant:
equalities = append(equalities, invariant)
case *interfaces.ValueInvariant:
equalities = append(equalities, invariant)
case *interfaces.CallFuncArgsValueInvariant:
equalities = append(equalities, invariant)
default:
return nil, nil, fmt.Errorf("unknown invariant type: %T", x)
}
}
// optimization: if we have zero generator invariants, we can
// discard the value invariants!
// NOTE: if exclusives do *not* contain nested generators, then
// we don't need to check for exclusives here, and the logic is
// much faster and simpler and can possibly solve more cases...
if len(generators) == 0 && len(exclusives) == 0 {
used := []int{}
for i, x := range equalities {
_, ok1 := x.(*interfaces.ValueInvariant)
_, ok2 := x.(*interfaces.CallFuncArgsValueInvariant)
if !ok1 && !ok2 {
continue
}
used = append(used, i) // mark equality as used up
}
logf("%s: got %d equalities left after %d used up", Name, len(equalities)-len(used), len(used))
// 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:]...)
}
}
// append the generators at the end
// (they can go in any order, but it's more optimal this way)
equalities = append(equalities, generators...)
return equalities, exclusives, nil
}
logf("%s: invariants:", Name)
for i, x := range invariants {
logf("invariant(%d): %T: %s", i, x, x)
}
solved := make(map[interfaces.Expr]*types.Type)
// iterate through all invariants, flattening and sorting the list...
equalities, exclusives, err := process(invariants)
if err != nil {
return nil, err
}
// XXX: if these partials all shared the same variable definition, would
// it all work??? Maybe we don't even need the first map prefix...
listPartials := make(map[interfaces.Expr]map[interfaces.Expr]*types.Type)
mapPartials := make(map[interfaces.Expr]map[interfaces.Expr]*types.Type)
structPartials := make(map[interfaces.Expr]map[interfaces.Expr]*types.Type)
funcPartials := make(map[interfaces.Expr]map[interfaces.Expr]*types.Type)
callPartials := make(map[interfaces.Expr]map[interfaces.Expr]*types.Type)
isSolvedFn := func(solved map[interfaces.Expr]*types.Type) (map[interfaces.Expr]struct{}, bool) {
unsolved := make(map[interfaces.Expr]struct{})
result := true
for _, x := range expected {
if typ, exists := solved[x]; !exists || typ == nil {
result = false
unsolved[x] = struct{}{}
}
}
return unsolved, result
}
logf("%s: starting loop with %d equalities", Name, len(equalities))
// run until we're solved, stop consuming equalities, or type clash
Loop:
for {
logf("%s: iterate...", Name)
if len(equalities) == 0 && len(exclusives) == 0 {
break // we're done, nothing left
}
used := []int{}
for i, x := range equalities {
logf("%s: match(%T): %+v", Name, x, x)
// TODO: could each of these cases be implemented as a
// method on the Invariant type to simplify this code?
switch eq := x.(type) {
// trivials
case *interfaces.EqualsInvariant:
typ, exists := solved[eq.Expr]
if !exists {
solved[eq.Expr] = eq.Type // yay, we learned something!
used = append(used, i) // mark equality as used up
logf("%s: solved trivial equality", Name)
continue
}
// we already specified this, so check the repeat is consistent
if err := typ.Cmp(eq.Type); err != nil {
// this error shouldn't happen unless we purposefully
// try to trick the solver, or we're in a recursive try
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with equals")
}
used = append(used, i) // mark equality as duplicate
logf("%s: duplicate trivial equality", Name)
continue
// partials
case *interfaces.EqualityWrapListInvariant:
if _, exists := listPartials[eq.Expr1]; !exists {
listPartials[eq.Expr1] = make(map[interfaces.Expr]*types.Type)
}
if typ, exists := solved[eq.Expr1]; exists {
// wow, now known, so tell the partials!
// TODO: this assumes typ is a list, is that guaranteed?
listPartials[eq.Expr1][eq.Expr2Val] = typ.Val
}
// can we add to partials ?
for _, y := range []interfaces.Expr{eq.Expr2Val} {
typ, exists := solved[y]
if !exists {
continue
}
t, exists := listPartials[eq.Expr1][y]
if !exists {
listPartials[eq.Expr1][y] = typ // learn!
continue
}
if err := t.Cmp(typ); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with partial list val")
}
}
// can we solve anything?
var ready = true // assume ready
typ := &types.Type{
Kind: types.KindList,
}
valTyp, exists := listPartials[eq.Expr1][eq.Expr2Val]
if !exists {
ready = false // nope!
} else {
typ.Val = valTyp // build up typ
}
if ready {
if t, exists := solved[eq.Expr1]; exists {
if err := t.Cmp(typ); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with list")
}
}
// sub checks
if t, exists := solved[eq.Expr2Val]; exists {
if err := t.Cmp(typ.Val); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with list val")
}
}
solved[eq.Expr1] = typ // yay, we learned something!
solved[eq.Expr2Val] = typ.Val // yay, we learned something!
used = append(used, i) // mark equality as used up
logf("%s: solved list wrap partial", Name)
continue
}
case *interfaces.EqualityWrapMapInvariant:
if _, exists := mapPartials[eq.Expr1]; !exists {
mapPartials[eq.Expr1] = make(map[interfaces.Expr]*types.Type)
}
if typ, exists := solved[eq.Expr1]; exists {
// wow, now known, so tell the partials!
// TODO: this assumes typ is a map, is that guaranteed?
mapPartials[eq.Expr1][eq.Expr2Key] = typ.Key
mapPartials[eq.Expr1][eq.Expr2Val] = typ.Val
}
// can we add to partials ?
for _, y := range []interfaces.Expr{eq.Expr2Key, eq.Expr2Val} {
typ, exists := solved[y]
if !exists {
continue
}
t, exists := mapPartials[eq.Expr1][y]
if !exists {
mapPartials[eq.Expr1][y] = typ // learn!
continue
}
if err := t.Cmp(typ); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with partial map key/val")
}
}
// can we solve anything?
var ready = true // assume ready
typ := &types.Type{
Kind: types.KindMap,
}
keyTyp, exists := mapPartials[eq.Expr1][eq.Expr2Key]
if !exists {
ready = false // nope!
} else {
typ.Key = keyTyp // build up typ
}
valTyp, exists := mapPartials[eq.Expr1][eq.Expr2Val]
if !exists {
ready = false // nope!
} else {
typ.Val = valTyp // build up typ
}
if ready {
if t, exists := solved[eq.Expr1]; exists {
if err := t.Cmp(typ); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with map")
}
}
// sub checks
if t, exists := solved[eq.Expr2Key]; exists {
if err := t.Cmp(typ.Key); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with map key")
}
}
if t, exists := solved[eq.Expr2Val]; exists {
if err := t.Cmp(typ.Val); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with map val")
}
}
solved[eq.Expr1] = typ // yay, we learned something!
solved[eq.Expr2Key] = typ.Key // yay, we learned something!
solved[eq.Expr2Val] = typ.Val // yay, we learned something!
used = append(used, i) // mark equality as used up
logf("%s: solved map wrap partial", Name)
continue
}
case *interfaces.EqualityWrapStructInvariant:
if _, exists := structPartials[eq.Expr1]; !exists {
structPartials[eq.Expr1] = make(map[interfaces.Expr]*types.Type)
}
if typ, exists := solved[eq.Expr1]; exists {
// wow, now known, so tell the partials!
// TODO: this assumes typ is a struct, is that guaranteed?
if len(typ.Ord) != len(eq.Expr2Ord) {
return nil, fmt.Errorf("struct field count differs")
}
for i, name := range eq.Expr2Ord {
expr := eq.Expr2Map[name] // assume key exists
structPartials[eq.Expr1][expr] = typ.Map[typ.Ord[i]] // assume key exists
}
}
// can we add to partials ?
for name, y := range eq.Expr2Map {
typ, exists := solved[y]
if !exists {
continue
}
t, exists := structPartials[eq.Expr1][y]
if !exists {
structPartials[eq.Expr1][y] = typ // learn!
continue
}
if err := t.Cmp(typ); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with partial struct field: %s", name)
}
}
// can we solve anything?
var ready = true // assume ready
typ := &types.Type{
Kind: types.KindStruct,
}
typ.Map = make(map[string]*types.Type)
for name, y := range eq.Expr2Map {
t, exists := structPartials[eq.Expr1][y]
if !exists {
ready = false // nope!
break
}
typ.Map[name] = t // build up typ
}
if ready {
typ.Ord = eq.Expr2Ord // known order
if t, exists := solved[eq.Expr1]; exists {
if err := t.Cmp(typ); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with struct")
}
}
// sub checks
for name, y := range eq.Expr2Map {
if t, exists := solved[y]; exists {
if err := t.Cmp(typ.Map[name]); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with struct field: %s", name)
}
}
}
solved[eq.Expr1] = typ // yay, we learned something!
// we should add the other expr's in too...
for name, y := range eq.Expr2Map {
solved[y] = typ.Map[name] // yay, we learned something!
}
used = append(used, i) // mark equality as used up
logf("%s: solved struct wrap partial", Name)
continue
}
case *interfaces.EqualityWrapFuncInvariant:
if _, exists := funcPartials[eq.Expr1]; !exists {
funcPartials[eq.Expr1] = make(map[interfaces.Expr]*types.Type)
}
if typ, exists := solved[eq.Expr1]; exists {
// wow, now known, so tell the partials!
// TODO: this assumes typ is a func, is that guaranteed?
if len(typ.Ord) != len(eq.Expr2Ord) {
return nil, fmt.Errorf("func arg count differs")
}
for i, name := range eq.Expr2Ord {
expr := eq.Expr2Map[name] // assume key exists
funcPartials[eq.Expr1][expr] = typ.Map[typ.Ord[i]] // assume key exists
}
funcPartials[eq.Expr1][eq.Expr2Out] = typ.Out
}
// can we add to partials ?
for name, y := range eq.Expr2Map {
typ, exists := solved[y]
if !exists {
continue
}
t, exists := funcPartials[eq.Expr1][y]
if !exists {
funcPartials[eq.Expr1][y] = typ // learn!
continue
}
if err := t.Cmp(typ); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with partial func arg: %s", name)
}
}
for _, y := range []interfaces.Expr{eq.Expr2Out} {
typ, exists := solved[y]
if !exists {
continue
}
t, exists := funcPartials[eq.Expr1][y]
if !exists {
funcPartials[eq.Expr1][y] = typ // learn!
continue
}
if err := t.Cmp(typ); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with partial func arg")
}
}
// can we solve anything?
var ready = true // assume ready
typ := &types.Type{
Kind: types.KindFunc,
}
typ.Map = make(map[string]*types.Type)
for name, y := range eq.Expr2Map {
t, exists := funcPartials[eq.Expr1][y]
if !exists {
ready = false // nope!
break
}
typ.Map[name] = t // build up typ
}
outTyp, exists := funcPartials[eq.Expr1][eq.Expr2Out]
if !exists {
ready = false // nope!
} else {
typ.Out = outTyp // build up typ
}
if ready {
typ.Ord = eq.Expr2Ord // known order
if t, exists := solved[eq.Expr1]; exists {
if err := t.Cmp(typ); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with func")
}
}
// sub checks
for name, y := range eq.Expr2Map {
if t, exists := solved[y]; exists {
if err := t.Cmp(typ.Map[name]); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with func arg: %s", name)
}
}
}
if t, exists := solved[eq.Expr2Out]; exists {
if err := t.Cmp(typ.Out); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with func out")
}
}
solved[eq.Expr1] = typ // yay, we learned something!
// we should add the other expr's in too...
for name, y := range eq.Expr2Map {
solved[y] = typ.Map[name] // yay, we learned something!
}
solved[eq.Expr2Out] = typ.Out // yay, we learned something!
used = append(used, i) // mark equality as used up
logf("%s: solved func wrap partial", Name)
continue
}
case *interfaces.EqualityWrapCallInvariant:
// the logic is slightly different here, because
// we can only go from the func type to the call
// type as we can't do the reverse determination
if _, exists := callPartials[eq.Expr2Func]; !exists {
callPartials[eq.Expr2Func] = make(map[interfaces.Expr]*types.Type)
}
if typ, exists := solved[eq.Expr2Func]; exists {
// wow, now known, so tell the partials!
if typ.Kind != types.KindFunc {
return nil, fmt.Errorf("expected: %s, got: %s", types.KindFunc, typ.Kind)
}
callPartials[eq.Expr2Func][eq.Expr1] = typ.Out
}
typ, ready := callPartials[eq.Expr2Func][eq.Expr1]
if ready { // ready to solve
if t, exists := solved[eq.Expr1]; exists {
if err := t.Cmp(typ); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with call")
}
}
// sub checks
if t, exists := solved[eq.Expr2Func]; exists {
if err := t.Out.Cmp(typ); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with call out")
}
}
solved[eq.Expr1] = typ // yay, we learned something!
used = append(used, i) // mark equality as used up
logf("%s: solved call wrap partial", Name)
continue
}
// regular matching
case *interfaces.EqualityInvariant:
typ1, exists1 := solved[eq.Expr1]
typ2, exists2 := solved[eq.Expr2]
if !exists1 && !exists2 { // neither equality connects
// can't learn more from this equality yet
// nothing is known about either side of it
continue
}
if exists1 && exists2 { // both equalities already connect
// both sides are already known-- are they the same?
if err := typ1.Cmp(typ2); err != nil {
return nil, errwrap.Wrapf(err, "can't unify, invariant illogicality with equality")
}
used = append(used, i) // mark equality as used up
logf("%s: duplicate regular equality", Name)
continue
}
if exists1 && !exists2 { // first equality already connects
solved[eq.Expr2] = typ1 // yay, we learned something!
used = append(used, i) // mark equality as used up
logf("%s: solved regular equality", Name)
continue
}
if exists2 && !exists1 { // second equality already connects
solved[eq.Expr1] = typ2 // yay, we learned something!
used = append(used, i) // mark equality as used up
logf("%s: solved regular equality", Name)
continue
}
panic("reached unexpected code")
case *interfaces.GeneratorInvariant:
// this invariant can generate new ones
// optimization: we want to run the generators
// last (but before the exclusives) because
// they take longer to run. So as long as we've
// made progress this time around, don't run
// this just yet, there's still time left...
if len(used) > 0 {
continue
}
// If this returns nil, we add the invariants
// it returned and we remove it from the list.
// If we error, it's because we don't have any
// new information to provide at this time...
// XXX: should we pass in `invariants` instead?
gi, err := eq.Func(equalities, solved)
if err != nil {
continue
}
eqs, exs, err := process(gi) // process like at the top
if err != nil {
// programming error?
return nil, errwrap.Wrapf(err, "processing error")
}
equalities = append(equalities, eqs...)
exclusives = append(exclusives, exs...)
used = append(used, i) // mark equality as used up
logf("%s: solved `generator` equality", Name)
continue
// wtf matching
case *interfaces.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
case *interfaces.ValueInvariant:
// don't consume these, they're stored in case
// a generator invariant wants to read them...
continue
case *interfaces.CallFuncArgsValueInvariant:
// don't consume these, they're stored in case
// a generator invariant wants to read them...
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...
_, isSolved := isSolvedFn(solved)
if isSolved {
logf("%s: solved early with %d exclusives left!", Name, len(exclusives))
} else {
logf("%s: unsolved with %d exclusives left!", Name, len(exclusives))
if debug {
for i, x := range exclusives {
logf("%s: exclusive(%d) left: %s", Name, i, x)
}
}
}
// check for consistency against remaining invariants
logf("%s: checking for consistency against %d exclusives...", Name, len(exclusives))
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 {
logf("exclusive invar failed: %+v", invar)
return nil, errwrap.Wrapf(err, "inconsistent exclusive")
}
if !match {
continue
}
done = append(done, i)
}
logf("%s: removed %d consistent exclusives...", Name, len(done))
// 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 we removed any exclusives, then we can start over.
if len(done) > 0 {
continue Loop
}
// If we don't have any exclusives left, then we don't
// need the Value invariants... This logic is the same
// as in process() but it's duplicated here because we
// want it to happen at this stage as well. We can try
// and clean up the duplication and improve the logic.
// NOTE: We should probably check that there aren't any
// generators left in the equalities, but since we have
// already tried to use them up, it is probably safe to
// unblock the solver if it's only ValueInvatiant left.
if len(exclusives) == 0 || isSolved { // either is okay
used := []int{}
for i, x := range equalities {
_, ok1 := x.(*interfaces.ValueInvariant)
_, ok2 := x.(*interfaces.CallFuncArgsValueInvariant)
if !ok1 && !ok2 {
continue
}
used = append(used, i) // mark equality as used up
}
logf("%s: got %d equalities left after %d value invariants used up", Name, len(equalities)-len(used), len(used))
// 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:]...)
}
if len(used) > 0 {
continue Loop
}
}
if len(exclusives) == 0 && isSolved { // old generators
used := []int{}
for i, x := range equalities {
_, ok := x.(*interfaces.GeneratorInvariant)
if !ok {
continue
}
used = append(used, i) // mark equality as used up
}
logf("%s: got %d equalities left after %d generators used up", Name, len(equalities)-len(used), len(used))
// 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:]...)
}
if len(used) > 0 {
continue Loop
}
}
// 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 := &interfaces.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)
}
}
// 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 for accuracy, but in our case via the
// simplify method) so that if we're lucky, we rarely
// need to run the raw exclusive combinatorial solver,
// which is slow.
logf("%s: attempting to simplify %d exclusives...", Name, len(exclusives))
done = []int{} // clear for re-use
simplified := []interfaces.Invariant{}
for i, invar := range exclusives {
// The partialSolutions don't contain any other
// exclusives... We look at each individually.
s, err := invar.Simplify(partialSolutions) // XXX: pass in the solver?
if err != nil {
logf("exclusive simplification failed: %+v", invar)
continue
}
done = append(done, i)
simplified = append(simplified, s...)
}
logf("%s: simplified %d exclusives...", Name, len(done))
// 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:]...)
}
// Add new equalities and exclusives onto state globals.
eqs, exs, err := process(simplified) // process like at the top
if err != nil {
// programming error?
return nil, errwrap.Wrapf(err, "processing error")
}
equalities = append(equalities, eqs...)
exclusives = append(exclusives, exs...)
// If we removed any exclusives, then we can start over.
if len(done) > 0 {
continue Loop
}
// TODO: We could try and replace our combinatorial
// exclusive solver with a real SAT solver algorithm.
if !AllowRecursion || len(exclusives) > RecursionInvariantLimit {
logf("%s: %d solved, %d unsolved, and %d exclusives left", Name, len(solved), len(equalities), len(exclusives))
for i, eq := range equalities {
logf("%s: (%d) equality: %s", Name, i, eq)
}
for i, ex := range exclusives {
logf("%s: (%d) exclusive: %s", Name, i, ex)
}
// these can be very slow, so try to avoid them
return nil, fmt.Errorf("only recursive solutions left")
}
// 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...)
// FIXME: implement RecursionDepthLimit
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
logf("%s: ================ ambiguity ================", Name)
unsolved, isSolved := isSolvedFn(solved)
logf("%s: isSolved: %+v", Name, isSolved)
for _, x := range equalities {
logf("%s: unsolved equality: %+v", Name, x)
}
for x := range unsolved {
logf("%s: unsolved expected: %+v", Name, x)
}
return nil, ErrAmbiguous
}
// 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 := []*interfaces.EqualsInvariant{}
// FIXME: can we do this loop in a deterministic, sorted way?
for expr, typ := range solved {
invar := &interfaces.EqualsInvariant{
Expr: expr,
Type: typ,
}
solutions = append(solutions, invar)
}
return &InvariantSolution{
Solutions: solutions,
}, nil
}