add GPU fallback example

06_gpu_and_ml/gpu_fallbacks.py

@@ -0,0 +1,47 @@
+import subprocess
+
+import modal
+
+app = modal.App("example-gpu-fallbacks")
+
+# # Set "fallback" GPUs
+#
+# GPU availabilities on Modal can fluctuate, especially for
+# tightly-constrained requests, like for eight co-located GPUs
+# in a specific region.
+#
+# If your code can run on multiple different GPUs, you can specify
+# your GPU request as a list, in order of preference, and whenever
+# your Function scales up, we will try to schedule it on each requested GPU type in order.
+#
+# The code below demonstrates the usage of the `gpu` parameter with a list of GPUs.
+
+
+@app.function(
+    gpu=["h100", "a100", "any"],  # "any" means any of L4, A10, or T4
+    max_inputs=1,  # new container each input, so we re-roll the GPU dice every time
+)
+async def remote(_idx):
+    gpu = subprocess.run(
+        ["nvidia-smi", "--query-gpu=name", "--format=csv,noheader"],
+        check=True,
+        text=True,
+        stdout=subprocess.PIPE,
+    ).stdout.strip()
+    print(gpu)
+    return gpu
+
+
+@app.local_entrypoint()
+def local(count: int = 32):
+    from collections import Counter
+
+    gpu_counter = Counter(
+        remote.map([i for i in range(count)], order_outputs=False)
+    )
+    print(f"ran {gpu_counter.total()} times")
+    print(f"on the following {len(gpu_counter.keys())} GPUs:", end="\n")
+    print(
+        *[f"{gpu.rjust(32)}: {'🔥' * ct}" for gpu, ct in gpu_counter.items()],
+        sep="\n",
+    )