Softmax - 3.4 English

DPUCZDX8G for Zynq UltraScale+ MPSoCs Product Guide (PG338)

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3.4 English
This option allows the softmax function to be implemented in hardware. It is a separate accelerator which has its own interface and runtime with int8 input and floating-point output data format. This softmax HW option is just packaged into DPU wrapper.  The hardware implementation of softmax can be 160 times faster than a software implementation on MPSoC ARM in some application cases. Enabling this option depends on the customer chose algorithm model and desired throughput.
Note: The maximum categories number of hardware softmax is 1023. If the categories number is greater than 1023, it is recommend to use the software softmax. For more information, refer to the Vitis AI Library User Guide (UG1354) .

When softmax is enabled, an AXI master interface named SFM_M_AXI and an interrupt port named sfm_interrupt will appear in the DPUCZDX8G IP. The softmax module uses m_axi_dpu_aclk as the AXI clock for SFM_M_AXI as well as for computation.

The extra resources with Softmax enabled are listed in the following table.

Table 1. Extra Resources with Softmax
IP Name Extra LUTs Extra FFs Extra BRAMs Extra DSPs
Softmax 9580 8019 4 14