Rounding and Saturation Modes - 2023.2 English

The aie::set_rounding() and aie::set_saturation() APIs are used to set the rounding and saturation modes of the to_vector operation.

The aie::rounding_mode includes:

floor

Truncate LSB, always round down (towards negative infinity). Default.

ceil

Always round up (towards positive infinity).

positive_inf

Rounds halfway towards positive infinity.

negative_inf

Rounds halfway towards negative infinity.

symmetric_inf

Rounds halfway towards infinity (away from zero).

symmetric_zero

Rounds halfway towards zero (away from infinity).

conv_even

Rounds halfway towards nearest even number.

conv_odd

Rounds halfway towards nearest odd number.

The aie::saturation_mode includes:

none

No saturation is performed and the value is truncated on the MSB side. Default.

saturate

Controls saturation. Saturation rounds an n-bit signed value in the range

[- ( 2^(n-1) ) : + 2^(n-1) - 1 ]

. For example if n=8, the range would be [-128:127].

symmetric

Controls symmetric saturation. Symmetric saturation rounds an n-bit signed value in the range

[- ( 2^(n-1) -1 ) : + 2^(n-1) - 1 ]

. For example if n=8, the range would be [-127:127].

The rounding and saturation settings are applied on the AI Engine tile. The aie::get_rounding and aie::get_saturation methods can be used to get the current rounding and saturation modes.

aie::set_rounding(aie::rounding_mode::ceil);
aie::set_saturation(aie::saturation_mode::saturate);
aie::rounding_mode current_rnd=aie::get_rounding();
aie::saturation_mode current_sat=aie::get_saturation();
...
aie::set_rounding(aie::rounding_mode::floor);
aie::set_saturation(aie::saturation_mode::none);