Rectified Flow Scheduler Test (#220)

* added rf scheduler test

* rectified flow scheduler test added

* removed safetensors downloading

* replaced print statements with max_logging

Author: Serenagu525

tests/schedulers/rf_scheduler_test_ref/step_00_noisy_input.npy

@@ -0,0 +1,84 @@
+import jax.numpy as jnp
+from maxdiffusion.schedulers.scheduling_rectified_flow import FlaxRectifiedFlowMultistepScheduler
+import os
+from maxdiffusion import max_logging
+import torch
+import unittest
+from absl.testing import absltest
+import numpy as np
+
+
+
+class rfTest(unittest.TestCase):
+
+    def test_rf_steps(self):
+        # --- Simulation Parameters ---
+        latent_tensor_shape = (1, 256, 128) # Example latent tensor shape (Batch, Channels, Height, Width)
+        inference_steps_count = 5     # Number of steps for the denoising process
+
+        # --- Run the Simulation ---
+        max_logging.log("\n--- Simulating RectifiedFlowMultistepScheduler ---")
+
+        seed = 42
+        device = 'cpu'
+        max_logging.log(f"Sample shape: {latent_tensor_shape}, Inference steps: {inference_steps_count}, Seed: {seed}")
+
+        generator = torch.Generator(device=device).manual_seed(seed)
+
+        # 1. Instantiate the scheduler
+        config = {'_class_name': 'RectifiedFlowScheduler', '_diffusers_version': '0.25.1', 'num_train_timesteps': 1000, 'shifting': None, 'base_resolution': None, 'sampler': 'LinearQuadratic'}
+        flax_scheduler = FlaxRectifiedFlowMultistepScheduler.from_config(config)
+
+        # 2. Create and set initial state for the scheduler
+        flax_state = flax_scheduler.create_state()
+        flax_state = flax_scheduler.set_timesteps(flax_state, inference_steps_count, latent_tensor_shape)
+        max_logging.log("\nScheduler initialized.")
+        max_logging.log(f"  flax_state timesteps shape: {flax_state.timesteps.shape}")
+
+        # 3. Prepare the initial noisy latent sample
+        # In a real scenario, this would typically be pure random noise (e.g., N(0,1))
+        # For simulation, we'll generate it.
+
+        sample = jnp.array(torch.randn(latent_tensor_shape, generator=generator, dtype=torch.float32).to(device).numpy())
+        max_logging.log(f"\nInitial sample shape: {sample.shape}, dtype: {sample.dtype}")
+
+        # 4. Simulate the denoising loop
+        max_logging.log("\nStarting denoising loop:")
+        for i, t in enumerate(flax_state.timesteps):
+            max_logging.log(f"  Step {i+1}/{inference_steps_count}, Timestep: {t.item()}")
+
+            # Simulate model_output (e.g., noise prediction from a UNet)
+            model_output = jnp.array(torch.randn(latent_tensor_shape, generator=generator, dtype=torch.float32).to(device).numpy())
+
+            # Call the scheduler's step function
+            scheduler_output = flax_scheduler.step(
+                state=flax_state,
+                model_output=model_output,
+                timestep=t, # Pass the current timestep from the scheduler's sequence
+                sample=sample,
+                return_dict=True # Return a SchedulerOutput dataclass
+            )
+
+            sample = scheduler_output.prev_sample # Update the sample for the next step
+            flax_state = scheduler_output.state # Update the state for the next step
+
+            # Compare with pytorch implementation
+            base_dir = os.path.dirname(__file__)
+            ref_dir = os.path.join(base_dir, "rf_scheduler_test_ref")
+            ref_filename = os.path.join(ref_dir, f"step_{i+1:02d}.npy")
+            if os.path.exists(ref_filename):
+                pt_sample = np.load(ref_filename)
+                torch.testing.assert_close(np.array(sample), pt_sample)
+            else:
+                max_logging.log(f"Warning: Reference file not found: {ref_filename}")
+
+
+        max_logging.log("\nDenoising loop completed.")
+        max_logging.log(f"Final sample shape: {sample.shape}, dtype: {sample.dtype}")
+        max_logging.log(f"Final sample min: {sample.min().item():.4f}, max: {sample.max().item():.4f}")
+
+        max_logging.log("\nSimulation of RectifiedMultistepScheduler usage complete.")
+
+
+if __name__ == "__main__":
+  absltest.main()