From b9c954273daf16e16264cb332ad84a3cced2663e Mon Sep 17 00:00:00 2001
From: Dwight Lidman <dwight.lidman@arm.com>
Date: Wed, 18 Aug 2021 19:24:14 +0200
Subject: Reinstate recursion limit CLI option

This commit adds a CLI option for setting
the recursion limit. This option was originally
removed because it was considered unnecessary,
but in some cases of very large (enormous) networks,
a RecursionError is encountered during graph traversal.
A simple solution for issues like those is to manually
increase the recursion limit.

Signed-off-by: Dwight Lidman <dwight.lidman@arm.com>
Change-Id: Id0dbf68edf59b151abfa91783b5f8f021c1bb40f
---
 OPTIONS.md          | 16 ++++++++++++++++
 ethosu/vela/vela.py |  8 ++++++++
 2 files changed, 24 insertions(+)

diff --git a/OPTIONS.md b/OPTIONS.md
index 2420bbfe..6673ba5e 100644
--- a/OPTIONS.md
+++ b/OPTIONS.md
@@ -223,6 +223,22 @@ be a power of two and greater or equal to 16.
 vela network.tflite --allocation-alignment 128
 ```
 
+### Recursion Limit
+
+Sets the Python internal limit to depth of recursion. It may be
+necessary to increase this from the default for very large networks
+due to the recursive nature of the graph traversal algorithm.
+If Vela fails with a `RecursionError`, try increasing the limit using
+this option to see if it resolves the issue.  
+Please note that this option may not work as intended on Microsoft Windows
+systems, as there is a hard limit on thread stack size.  
+**Type: Integer**  
+**Default: 1000**
+
+```bash
+vela network.tflite --recursion-limit 2000
+```
+
 ## Verbose Print Options
 
 All of the options below are disabled by default and enabling them will add
diff --git a/ethosu/vela/vela.py b/ethosu/vela/vela.py
index b8a3b9f2..9e237f84 100644
--- a/ethosu/vela/vela.py
+++ b/ethosu/vela/vela.py
@@ -398,6 +398,12 @@ def main(args=None):
                 " operator inputs and outputs (default: %(default)s)"
             ),
         )
+        parser.add_argument(
+            "--recursion-limit",
+            type=int,
+            default=1000,
+            help="Set the recursion depth limit, may result in RecursionError if too low (default: %(default)s)",
+        )
         args = parser.parse_args(args=args)
 
         # Generate the supported ops report and exit
@@ -431,6 +437,8 @@ def main(args=None):
                 if v.startswith("verbose") and v != "verbose_all":
                     setattr(args, v, True)
 
+        sys.setrecursionlimit(args.recursion_limit)
+
         arch = architecture_features.ArchitectureFeatures(
             vela_config_files=args.config,
             system_config=args.system_config,
-- 
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