vec_rsqrt
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IBM Power 9 64-bit (64 bits)/ VSX View official documentation

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Purpose:

Purpose: Returns a vector containing a refined approximation of the reciprocal square roots of the corresponding elements of the source vector. This function provides an implementation-dependent greater precision than vec_rsqrte.

Result value: Each element of output contains a refined approximation of the reciprocal square root of the corresponding element of a.

Endian considerations: None.

Notes:

The example implementations assume that a register h initially contains the floating-point value 0.5 in each element (single- or double-precision as appropriate).
For finite square roots, this intrinsic guarantees at least 23 bits of accuracy for single-precision floating point, and at least 52 bits of accuracy for double-precision floating point.

Result:

vector double

Prototypes

Assembly Instruction:

xvrsqrtedp

Usage:


									
										vector double result =
									
									vec_rsqrt(
									
										vector double a
									)

Performance Metrics:

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Get access to detailed performance metrics including latency, throughput, and CPU-specific benchmarks for this intrinsic.

Example:

#include <altivec.h>
#include <stdio.h>
int main() {
 vector double a = {
  4.0, 9.0
 };
 vector double r = vec_rsqrt(a);
 double resultArray[2];
 vec_st(r, 0, resultArray);
 for (int i = 0; i < 2; i++) {
   printf("%f ", resultArray[i]);
  }
  printf("\n");

  return 0;
 }