# VEXP2PD — Approximation to the Exponential 2^x of Packed Double-Precision Floating-Point Values with Less Than 2^-23 Relative Error

Opcode/Instruction Op/En 64/32 bit Mode Support CPUID Feature Flag Description
EVEX.512.66.0F38.W1 C8 /r VEXP2PD zmm1 {k1}{z}, zmm2/m512/m64bcst {sae} A V/V AVX512ER Computes approximations to the exponential 2^x (with less than 2^-23 of maximum relative error) of the packed double-precision floating-point values from zmm2/m512/m64bcst and stores the floating-point result in zmm1with writemask k1.

## Instruction Operand Encoding ¶

 Op/En Tuple Type Operand 1 Operand 2 Operand 3 Operand 4 A Full ModRM:reg (r, w) ModRM:r/m (r) NA NA

### Description ¶

Computes the approximate base-2 exponential evaluation of the double-precision floating-point values in the source operand (the second operand) and stores the results to the destination operand (the first operand) using the writemask k1. The approximate base-2 exponential is evaluated with less than 2^-23 of relative error.

Denormal input values are treated as zeros and do not signal #DE, irrespective of MXCSR.DAZ. Denormal results are flushed to zeros and do not signal #UE, irrespective of MXCSR.FTZ.

The source operand is a ZMM register, a 512-bit memory location or a 512-bit vector broadcasted from a 64-bit memory location. The destination operand is a ZMM register, conditionally updated using writemask k1.

EVEX.vvvv is reserved and must be 1111b otherwise instructions will #UD.

### Operation ¶

#### VEXP2PD ¶

```(KL, VL) = (8, 512)
FOR j←0 TO KL-1
i←j * 64
IF k1[j] OR *no writemask* THEN
IF (EVEX.b = 1) AND (SRC *is memory*)
THEN DEST[i+63:i]←EXP2_23_DP(SRC[63:0])
ELSE DEST[i+63:i]←EXP2_23_DP(SRC[i+63:i])
FI;
ELSE
THEN *DEST[i+63:i] remains unchanged*
DEST[i+63:i] ← 0
FI;
FI;
ENDFOR;
```

### Intel C/C++ Compiler Intrinsic Equivalent ¶

```VEXP2PD __m512d _mm512_exp2a23_round_pd (__m512d a, int sae);
```
```VEXP2PD __m512d _mm512_mask_exp2a23_round_pd (__m512d a, __mmask8 m, __m512d b, int sae);
```
```VEXP2PD __m512d _mm512_maskz_exp2a23_round_pd ( __mmask8 m, __m512d b, int sae);
```

### SIMD Floating-Point Exceptions ¶

Invalid (if SNaN input), Overflow

### Other Exceptions ¶

See Exceptions Type E2.