Function arm_nn_sqrt_f32

Function Documentation

arm_cmsis_nn_status arm_nn_sqrt_f32(const float32_t *input, float32_t *output, int32_t block_size)

Elementwise square root.

The value path is scalar on every toolchain, because Helium has no vector square root. armclang and ATfE do vectorize the surrounding special-value classification; the results are bit-identical to the GCC scalar build, verified by executing both toolchains’ objects (#295). Normal positive inputs evaluate sqrtf(x), which IEEE 754 makes correctly rounded, so results are bit-exact to a float64 reference. Subnormal inputs follow FPSCR.FZ: where flush-to-zero is set - the Corstone-300 FVP default, and any host binary linked at -Ofast, where crtfastmath sets DAZ and FTZ - a subnormal input reads as zero and the result is +0. The float16 pair is immune, because it widens to a normal float32 first. 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 0x7FC00000, NaN -> the same NaN with the quiet bit set (sign and payload kept).

Parameters:

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

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

  • block_size – [in] Number of elements to process.

Returns:

ARM_CMSIS_NN_SUCCESS on success or ARM_CMSIS_NN_ARG_ERROR on invalid arguments.