function gammaCorrection( x ) {
	if ( x < 10.0 ) {
		return NaN;
	}
	// Check for underflow...
	if ( x >= XMAX ) {
		return 0.0;
	}
	if ( x < XBIG ) {
		return dceval( (2.0*pow( 10.0/x, 2.0 )) - 1.0 ) / x;
	}
	return 1.0 / (x * 12.0);
}
Computes the log gamma correction factor for `x >= 10`.

```tex
\log(\gamma(x)) = \log(\sqrt{2*\Pi}) + (x-0.5) \cdot \log(x) - x \operatorname{R9LGMC}(x).
```

@private
@param {number} x - input value
@returns {number} correction value