Function arm_nn_sqrt_f16

Function Documentation

arm_cmsis_nn_status arm_nn_sqrt_f16(const float16_t *input, float16_t *output, int32_t block_size)

Elementwise square root of a float16 tensor.

The value path is scalar on every toolchain, because Helium has no vector square root; armclang and ATfE vectorize the surrounding classification into an MVE loop and produce bit-identical results, verified by executing their objects (#295). Each element is widened to float32, sqrtf is evaluated there and the result is rounded once to float16. Verified exhaustively: for every positive finite float16 input, subnormals included, the result is the correctly rounded float16 of the float64 square root (0 ulp, #295). Widening first also makes this pair immune to FPSCR.FZ, which flushes float32 subnormals in the f32 pair. Special values are decided on the bit pattern and returned as literals, independent of -ffinite-math-only and FPSCR.DN: +0 -> +0, -0 -> -0, +Inf -> +Inf, negative (including -Inf) -> quiet NaN 0x7E00, NaN -> the same NaN with the quiet bit set (sign and payload kept).

Parameters:

  • input – [in] Pointer to the input tensor.

  • output – [out] Pointer to the output tensor; may alias input.

  • block_size – [in] Number of tensor elements.

Returns:

ARM_CMSIS_NN_SUCCESS on success or ARM_CMSIS_NN_ARG_ERROR on invalid arguments.