disable dpm multistep solver with image2image

swift/StableDiffusion/pipeline/DPMSolverMultistepScheduler.swift

@@ -23,16 +23,12 @@ public final class DPMSolverMultistepScheduler: Scheduler {
     public let betas: [Float]
     public let alphas: [Float]
     public let alphasCumProd: [Float]
-    private let timeSteps: [Int]
+    public let timeSteps: [Int]
 
     public let alpha_t: [Float]
     public let sigma_t: [Float]
     public let lambda_t: [Float]
     
-    public var allTimeSteps: [Int] {
-        timeSteps
-    }
-    
     public let solverOrder = 2
     private(set) var lowerOrderStepped = 0
     
@@ -183,4 +179,9 @@ public final class DPMSolverMultistepScheduler: Scheduler {
         
         return prevSample
     }
+    
+    /// This scheduler does not support image2image strength value.
+    public func calculateTimesteps(strength: Float?) -> [Int] {
+        timeSteps
+    }
 }

swift/StableDiffusion/pipeline/Scheduler.swift

@@ -12,7 +12,7 @@ public protocol Scheduler {
     var inferenceStepCount: Int { get }
     
     /// Training diffusion time steps index by inference time step
-    var allTimeSteps: [Int] { get }
+    var timeSteps: [Int] { get }
 
     /// Training diffusion time steps index by inference time step
     func calculateTimesteps(strength: Float?) -> [Int]
@@ -94,9 +94,9 @@ public extension Scheduler {
 public extension Scheduler {
     
     func calculateTimesteps(strength: Float?) -> [Int] {
-        guard let strength else { return allTimeSteps.reversed() }
+        guard let strength else { return timeSteps.reversed() }
         let startStep = Int(Float(inferenceStepCount) * strength)
-        let acutalTimesteps = Array(allTimeSteps[0..<startStep].reversed())
+        let acutalTimesteps = Array(timeSteps[0..<startStep].reversed())
         return acutalTimesteps
     }
 }
@@ -127,11 +127,7 @@ public final class PNDMScheduler: Scheduler {
     public let betas: [Float]
     public let alphas: [Float]
     public let alphasCumProd: [Float]
-    private let timeSteps: [Int]
-    
-    public var allTimeSteps: [Int] {
-        timeSteps
-    }
+    public let timeSteps: [Int]
 
     // Internal state
     var counter: Int

swift/StableDiffusion/pipeline/StableDiffusionPipeline.swift

@@ -23,6 +23,7 @@ public struct StableDiffusionPipeline: ResourceManaging {
     
     public enum Error: String, Swift.Error {
         case startingImageProvidedWithoutEncoder
+        case schedulerNotSupportedWithImage2Image
     }
 
     /// Model to generate embeddings for tokenized input text
@@ -130,7 +131,7 @@ public struct StableDiffusionPipeline: ResourceManaging {
         seed: UInt32 = 0,
         guidanceScale: Float = 7.5,
         disableSafety: Bool = false,
-        scheduler: StableDiffusionScheduler = .pndmScheduler,
+        scheduler schedulerType: StableDiffusionScheduler = .pndmScheduler,
         progressHandler: (Progress) -> Bool = { _ in true }
     ) throws -> [CGImage?] {
 
@@ -153,7 +154,7 @@ public struct StableDiffusionPipeline: ResourceManaging {
 
         /// Setup schedulers
         let scheduler: [Scheduler] = (0..<imageCount).map { _ in
-            switch scheduler {
+            switch schedulerType {
             case .pndmScheduler: return PNDMScheduler(stepCount: stepCount)
             case .dpmSolverMultistepScheduler: return DPMSolverMultistepScheduler(stepCount: stepCount)
             }
@@ -169,6 +170,13 @@ public struct StableDiffusionPipeline: ResourceManaging {
             guard let encoder else {
                 throw Error.startingImageProvidedWithoutEncoder
             }
+            switch schedulerType {
+            case .pndmScheduler:
+                break
+            case .dpmSolverMultistepScheduler:
+                throw Error.schedulerNotSupportedWithImage2Image
+            }
+            
             let noiseTuples = generateImage2ImageLatentSamples(imageCount, stdev: 1, seed: seed)
             latents = try noiseTuples.map({
                 try encoder.encode(
@@ -184,7 +192,7 @@ public struct StableDiffusionPipeline: ResourceManaging {
         }
 
         // De-noising loop
-        let timeSteps = scheduler[0].calculateTimesteps(strength: timestepStrength)
+        let timeSteps: [Int] = scheduler[0].calculateTimesteps(strength: timestepStrength)
         for (step,t) in timeSteps.enumerated() {
 
             // Expand the latents for classifier-free guidance