From 6f72526b3c74c0e64075563be2ddf7f9708ad12c Mon Sep 17 00:00:00 2001
From: Michael McGeagh <michael.mcgeagh@arm.com>
Date: Thu, 3 Dec 2020 15:21:36 +0000
Subject: MLBEDSW-3685 Fix dangerous default value usage

Pylint W0102:
When a mutable value as list or dictionary is detected in a
default value for an argument.

Replace detected instances with None, and upon checking for None, sets
the default accordingly

Signed-off-by: Michael McGeagh <michael.mcgeagh@arm.com>
Change-Id: I4eb73d07d01d4cdefa586eb71b9c76746eee3b11
---
 ethosu/vela/npu_performance.py | 43 +++++++++++++++++++++---------------------
 1 file changed, 22 insertions(+), 21 deletions(-)

(limited to 'ethosu/vela/npu_performance.py')

diff --git a/ethosu/vela/npu_performance.py b/ethosu/vela/npu_performance.py
index 9a6e8cd2..d28df97d 100644
--- a/ethosu/vela/npu_performance.py
+++ b/ethosu/vela/npu_performance.py
@@ -489,7 +489,7 @@ def estimate_memory_bandwidth(arch, mem_area, direction, tensor, block_size: Blo
     return bw * (max_burst_len / burst_len)
 
 
-def performance_metrics_for_pass(arch, ps, block_config=None, rewrite_list=[], force_outputs_to_fast_storage=False):
+def performance_metrics_for_pass(arch, ps, block_config=None, rewrite_list=None, force_outputs_to_fast_storage=False):
     if block_config is None:
         block_config = ps.block_config
     bws = make_bandwidth_array()
@@ -723,26 +723,27 @@ def performance_metrics_for_pass(arch, ps, block_config=None, rewrite_list=[], f
                 for tens in dma_op.inputs:
                     cycles[PassCycles.Npu] += tens.storage_size() / arch.memory_bandwidths_per_cycle[mem_area]
 
-    # apply the desired rewrites
-    for rewrite_op, tens, _, _, _, ps_to_rewrite in rewrite_list:
-        if ps != ps_to_rewrite:
-            continue
-        if rewrite_op == SchedulerRewrite.Nop:
-            pass  # these are fine, no bandwidth changes
-        elif rewrite_op in (SchedulerRewrite.ChangeTensorSubPurpose,):
-            if tens.purpose == TensorPurpose.FeatureMap:
-                bw = estimate_memory_bandwidth(
-                    arch,
-                    arch.fast_storage_mem_area,
-                    BandwidthDirection.Read,
-                    tens,
-                    ifm_block,
-                    replacement_read_bws[tens],
-                )
-            else:
-                bw = replacement_read_bws[tens]
-            bws[arch.fast_storage_mem_area][tens.purpose][BandwidthDirection.Read] += bw
-            replacement_read_bws[tens] = 0
+    if rewrite_list is not None:
+        # apply the desired rewrites
+        for rewrite_op, tens, _, _, _, ps_to_rewrite in rewrite_list:
+            if ps != ps_to_rewrite:
+                continue
+            if rewrite_op == SchedulerRewrite.Nop:
+                pass  # these are fine, no bandwidth changes
+            elif rewrite_op in (SchedulerRewrite.ChangeTensorSubPurpose,):
+                if tens.purpose == TensorPurpose.FeatureMap:
+                    bw = estimate_memory_bandwidth(
+                        arch,
+                        arch.fast_storage_mem_area,
+                        BandwidthDirection.Read,
+                        tens,
+                        ifm_block,
+                        replacement_read_bws[tens],
+                    )
+                else:
+                    bw = replacement_read_bws[tens]
+                bws[arch.fast_storage_mem_area][tens.purpose][BandwidthDirection.Read] += bw
+                replacement_read_bws[tens] = 0
 
     for tens in ps.outputs:
         if force_outputs_to_fast_storage:
-- 
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