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engine: realistic config bounds, enforced and served

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ConfigBounds (students 10-500, edgesPerNode 1-8, forwardProb 0-0.9,
triangleProb 0-1) caps what RunScenario accepts: a student does not
keep 150 close friendships and a guaranteed forward is not a real
base rate. numEducated gains its missing upper limit (numStudents).
Bounds-side validation also protects the public server from absurd
numStudents values. GET /api/config/default now returns
{config, bounds} so the frontend can drive its controls from the
same numbers; the frontend does not call it yet, so this commit
changes no UI behaviour.
This commit is contained in:
Justin Visser 2026-06-11 15:54:07 +02:00
parent 232faf892e
commit bd890384e5
7 changed files with 194 additions and 15 deletions
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77
internal/engine/scenario.go
View file

@ -50,6 +50,73 @@ func DefaultConfig() Config {
}
}
// IntBounds is an inclusive allowed range for an integer Config field.
type IntBounds struct {
Min int `json:"min"`
Max int `json:"max"`
}
// FloatBounds is an inclusive allowed range for a float Config field.
type FloatBounds struct {
Min float64 `json:"min"`
Max float64 `json:"max"`
}
// Bounds gives the allowed range for every absolute Config field. These
// are realism limits, not mathematical ones: a student does not keep 150
// close friendships, and a guaranteed forward is not a plausible base
// rate. numEducated and origin are relational (0..numStudents and
// 0..numStudents-1) and therefore not listed; seeds are unrestricted.
type Bounds struct {
NumStudents IntBounds `json:"numStudents"`
EdgesPerNode IntBounds `json:"edgesPerNode"`
TriangleProb FloatBounds `json:"triangleProb"`
ForwardProb FloatBounds `json:"forwardProb"`
}
// ConfigBounds returns the bounds the engine enforces. The frontend
// receives this verbatim (with the default config) and drives its
// sliders and clamping from the same numbers.
func ConfigBounds() Bounds {
return Bounds{
NumStudents: IntBounds{Min: 10, Max: 500},
EdgesPerNode: IntBounds{Min: 1, Max: 8},
TriangleProb: FloatBounds{Min: 0, Max: 1},
ForwardProb: FloatBounds{Min: 0, Max: 0.9},
}
}
// ValidateConfig rejects configs outside ConfigBounds or with relational
// fields out of range. Error messages contain the offending field's JSON
// name; the frontend matches on it to mark the right control invalid.
func ValidateConfig(config Config) error {
bounds := ConfigBounds()
if config.NumStudents < bounds.NumStudents.Min || config.NumStudents > bounds.NumStudents.Max {
return fmt.Errorf("scenario: need %d <= numStudents <= %d, got %d",
bounds.NumStudents.Min, bounds.NumStudents.Max, config.NumStudents)
}
if config.EdgesPerNode < bounds.EdgesPerNode.Min || config.EdgesPerNode > bounds.EdgesPerNode.Max {
return fmt.Errorf("scenario: need %d <= edgesPerNode <= %d, got %d",
bounds.EdgesPerNode.Min, bounds.EdgesPerNode.Max, config.EdgesPerNode)
}
if config.TriangleProb < bounds.TriangleProb.Min || config.TriangleProb > bounds.TriangleProb.Max {
return fmt.Errorf("scenario: need %v <= triangleProb <= %v, got %v",
bounds.TriangleProb.Min, bounds.TriangleProb.Max, config.TriangleProb)
}
if config.ForwardProb < bounds.ForwardProb.Min || config.ForwardProb > bounds.ForwardProb.Max {
return fmt.Errorf("scenario: need %v <= forwardProb <= %v, got %v",
bounds.ForwardProb.Min, bounds.ForwardProb.Max, config.ForwardProb)
}
if config.NumEducated < 0 || config.NumEducated > config.NumStudents {
return fmt.Errorf("scenario: need 0 <= numEducated <= %d students, got %d",
config.NumStudents, config.NumEducated)
}
if config.Origin < 0 || config.Origin >= config.NumStudents {
return fmt.Errorf("scenario: origin %d outside 0..%d", config.Origin, config.NumStudents-1)
}
return nil
}
// Result is the outcome of one scenario run.
type Result struct {
Strategy Strategy `json:"strategy"`
@ -77,14 +144,8 @@ func GraphEdges(config Config) ([][2]int, error) {
// cascade. Scenarios with the same config share the same world, so
// comparing strategies compares only the lever.
func RunScenario(config Config, strategy Strategy) (Result, error) {
if config.ForwardProb < 0 || config.ForwardProb > 1 {
return Result{}, fmt.Errorf("scenario: need 0 <= forwardProb <= 1, got %v", config.ForwardProb)
}
if config.Origin < 0 || config.Origin >= config.NumStudents {
return Result{}, fmt.Errorf("scenario: origin %d outside 0..%d", config.Origin, config.NumStudents-1)
}
if config.NumEducated < 0 {
return Result{}, fmt.Errorf("scenario: need numEducated >= 0, got %d", config.NumEducated)
if err := ValidateConfig(config); err != nil {
return Result{}, err
}
graph, err := HolmeKim(config.NumStudents, config.EdgesPerNode, config.TriangleProb, newRand(config.GraphSeed))