feat: unblock cpu training (#889)

* Update train_nsf_sim_cache_sid_load_pretrain.py

patch to unblock cpu training. CPU training took ~12 hours for me.

* Update train_nsf_sim_cache_sid_load_pretrain.py

Co-authored-by: Nato Boram <NatoBoram@users.noreply.github.com>

---------

Co-authored-by: 源文雨 <41315874+fumiama@users.noreply.github.com>
Co-authored-by: Nato Boram <NatoBoram@users.noreply.github.com>

train_nsf_sim_cache_sid_load_pretrain.py

@@ -67,8 +67,13 @@ class EpochRecorder:
 
 def main():
     n_gpus = torch.cuda.device_count()
+
     if torch.cuda.is_available() == False and torch.backends.mps.is_available() == True:
         n_gpus = 1
+    if n_gpus < 1:
+        # patch to unblock people without gpus. there is probably a better way.
+        print("NO GPU DETECTED: falling back to CPU - this may take a while")
+        n_gpus = 1
     os.environ["MASTER_ADDR"] = "localhost"
     os.environ["MASTER_PORT"] = str(randint(20000, 55555))
     children = []