MLBEDSW-4071: Power of two handling 16-bit tanh/sigmoid
Added special handling of power-of-two input scales for
16-bit tanh/sigmoid to align with the reference.
Change-Id: I87831bcd587623d7db7100e768905355c2c98e9d
Signed-off-by: Louis Verhaard <louis.verhaard@arm.com>
diff --git a/ethosu/vela/register_command_stream_generator.py b/ethosu/vela/register_command_stream_generator.py
index a4466c9..65801b8 100644
--- a/ethosu/vela/register_command_stream_generator.py
+++ b/ethosu/vela/register_command_stream_generator.py
@@ -17,6 +17,7 @@
# Register level (low-level) command stream generation for Ethos-U. Takes a list of NPU operations and generates
# all the register settings. Calculates dependencies between commands and inserts wait operations. And generates a bit
# stream suitable for interpretation by the Ethos-U processor.
+import math
from collections import defaultdict
from enum import Enum
from enum import IntEnum
@@ -640,12 +641,21 @@
rescale = 0x3000 * ifm_quant.scale_f32
if pool_op.ifm.data_type == NpuDataType.INT16:
# Calculate scale and shift for the output scale of 1/(3*4096)
- shift = 0
- max_rescale = np.iinfo(np.int16).max / 2
- while rescale <= max_rescale and shift <= 30:
- shift += 1
- rescale *= 2
- scale = int(rescale)
+ x_log2 = math.log2(ifm_quant.scale_f32)
+ rounded_log2 = int(round(x_log2))
+ is_power_of_two = abs(x_log2 - rounded_log2) < 0.001
+ shift = rounded_log2 + 12
+ if is_power_of_two and shift in (0, 1):
+ # Special handling if input scale is 1/2048 or 1/4096
+ scale = 3 << shift
+ shift = 0
+ else:
+ shift = 0
+ max_rescale = np.iinfo(np.int16).max / 2
+ while rescale <= max_rescale and shift <= 30:
+ shift += 1
+ rescale *= 2
+ scale = int(rescale)
else:
rescale_bits = len(bin(round_up_to_int(rescale))) - 2 + 1
scale, shift = scaling.quantise_pooling_scale(kernel.height * kernel.width, rescale_bits)