[moe] Add inv-sqrt LR schedule experiment for Good 10T gate

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: github-actions[bot]

experiments/grug/moe/inv_sqrt_lr.py

@@ -0,0 +1,68 @@
+# Copyright The Marin Authors
+# SPDX-License-Identifier: Apache-2.0
+
+"""Good 10T experiment: inv-sqrt LR schedule for MoE.
+
+Compares inverse-square-root learning-rate decay against the default cosine
+schedule on the standard MoE trial configuration. Everything else (model, data,
+resources, training steps) is identical to the cosine baseline in launch.py so
+the comparison is apples-to-apples.
+
+Tracking issue: https://github.com/marin-community/marin/issues/4028
+"""
+
+from fray.cluster import ResourceConfig
+from levanter.optim import AdamConfig
+from levanter.tracker.wandb import WandbConfig
+from marin.execution.executor import ExecutorStep, executor_main, this_output_path, versioned
+
+from experiments.grug.moe.launch import (
+    GRUG_MOE_TRIAL_MODEL,
+    GrugMoeLaunchConfig,
+    NEMOTRON_MIX_WITH_DEFAULT_VALIDATION,
+    _resolve_run_id,
+    run_grug_moe,
+)
+
+RESOLVED_RUN_ID = _resolve_run_id("grug-moe-inv-sqrt-lr")
+
+# Same optimizer as the cosine baseline but with inv_sqrt schedule. The decay
+# fraction is omitted because inv_sqrt decays continuously from peak rather
+# than using a cosine-style stable/decay split.
+INV_SQRT_OPTIMIZER = AdamConfig(
+    learning_rate=3e-3,
+    weight_decay=0.1,
+    lr_schedule="inv_sqrt",
+    min_lr_ratio=0.1,
+    warmup=1000,
+)
+
+grug_moe_inv_sqrt_lr = ExecutorStep(
+    name="grug/moe-inv-sqrt-lr",
+    fn=run_grug_moe,
+    config=GrugMoeLaunchConfig(
+        model=versioned(GRUG_MOE_TRIAL_MODEL),
+        data=NEMOTRON_MIX_WITH_DEFAULT_VALIDATION,
+        output_path=this_output_path(),
+        run_id=RESOLVED_RUN_ID,
+        resources=versioned(ResourceConfig.with_tpu("v5p-8")),
+        steps=versioned(2_000),
+        batch_size=versioned(512),
+        seed=versioned(0),
+        mp=versioned("params=float32,compute=bfloat16,output=bfloat16"),
+        tracker=WandbConfig(
+            project="marin",
+            tags=["grug", "moe", "inv-sqrt-lr", "good-10t"],
+            group="grug-moe-inv-sqrt-lr",
+            name=None,
+        ),
+        optimizer=versioned(INV_SQRT_OPTIMIZER),
+    ),
+)
+
+
+if __name__ == "__main__":
+    executor_main(
+        steps=[grug_moe_inv_sqrt_lr],
+        description="Good 10T: inv-sqrt LR schedule for MoE (issue #4028).",
+    )