log (sm4 - asm)
Component-wise log base 2.
| log[_sat] dest[.mask], [-]src0[_abs][.swizzle] |
|---|
| Item | Description |
|---|---|
| dest |
[in] The address of the result of the operation. dest = log2(src0) |
| src0 |
[in] The value for the operation. |
Remarks
Restrictions
- Follows limit theory.
- Error tolerance: If src0 is [0.5..2], absolue error must be no more than 2-21. If src0 is (0..0.5) or (2..+INF], relative error must be no more than 2-21.
The following table shows the results obtained when executing the instruction with various classes of numbers, assuming that neither overflow or underflow occurs. F means finite-real number.
| src | -inf | -F | -denorm | -0 | +0 | +denorm | +F | +inf | NaN |
|---|---|---|---|---|---|---|---|---|---|
| dest | NaN | NaN | -inf | -inf | -inf | -inf | F | +inf | NaN |
This instruction applies to the following shader stages:
| Vertex Shader | Geometry Shader | Pixel Shader |
|---|---|---|
| x | x | x |
Minimum Shader Model
This function is supported in the following shader models.
| Shader Model | Supported |
|---|---|
| Shader Model 5 | yes |
| Shader Model 4.1 | yes |
| Shader Model 4 | yes |
| Shader Model 3 (DirectX HLSL) | no |
| Shader Model 2 (DirectX HLSL) | no |
| Shader Model 1 (DirectX HLSL) | no |