add a message about new torch/xformers version and a way to upgrade by specifying a commandline flag

webui.py

@@ -8,6 +8,7 @@ import re
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.middleware.gzip import GZipMiddleware
+from packaging import version
 
 from modules import import_hook, errors, extra_networks
 from modules import extra_networks_hypernet, ui_extra_networks_hypernets, ui_extra_networks_textual_inversion
@@ -49,7 +50,32 @@ else:
     server_name = "0.0.0.0" if cmd_opts.listen else None
 
 
+def check_versions():
+    expected_torch_version = "1.13.1"
+
+    if version.parse(torch.__version__) < version.parse(expected_torch_version):
+        errors.print_error_explanation(f"""
+You are running torch {torch.__version__}.
+The program is tested to work with torch {expected_torch_version}.
+To reinstall the desired version, run with commandline flag --reinstall-torch.
+Beware that this will cause a lot of large files to be downloaded.
+        """.strip())
+
+    expected_xformers_version = "0.0.16rc425"
+    if shared.xformers_available:
+        import xformers
+
+        if version.parse(xformers.__version__) < version.parse(expected_xformers_version):
+            errors.print_error_explanation(f"""
+You are running xformers {xformers.__version__}.
+The program is tested to work with xformers {expected_xformers_version}.
+To reinstall the desired version, run with commandline flag --reinstall-xformers.
+            """.strip())
+
+
 def initialize():
+    check_versions()
+
     extensions.list_extensions()
     localization.list_localizations(cmd_opts.localizations_dir)