Approximation of exponential function and pow function in Java

FastApproximations.java

/**
 * Approximation of the Exponential Function
 * 
 * http://martin.ankerl.com/2007/02/11/optimized-exponential-functions-for-java/
 * http://nic.schraudolph.org/pubs/Schraudolph99.pdf
 */
private static double exp(final double val) {
    long tmp = (long) (1512775 * val + (1072693248 - 60801));
    return Double.longBitsToDouble(tmp << 32);
	
}
	
/**
 * Approximation of pow() function
 * 
 * http://martin.ankerl.com/2007/10/04/optimized-pow-approximation-for-java-and-c-c/
 */
public static double pow1(final double a, final double b) {
    final int x = (int) (Double.doubleToLongBits(a) << 32);
    final int y = (int) (b * (x - 1072632447) + 1072632447);
    return Double.longBitsToDouble(((long) y) << 32);
}

public static double pow2(final double a, final double b) {
    final long tmp = Double.doubleToLongBits(a);
    final long tmp2 = (long)(b * (tmp - 4606921280493453312L)) + 4606921280493453312L;
     return Double.longBitsToDouble(tmp2);
}