java.lang.Object
- micycle.peasygradients.utilities.fastLog.FastLog
- - micycle.peasygradients.utilities.fastLog.DFastLog

```
public class DFastLog
extends FastLog
```
Implementation of the ICSILog algorithm as described in O. Vinyals, G. Friedland, N. Mirghafori "Revisiting a basic function on current CPUs: A fast logarithm implementation with adjustable accuracy" (2007).
This class is based on the original algorithm description and a Java implementation by Hanns Holger Rutz. It has been adapted for use with double-precision data.
Note: log(float) is not provided as it is dynamically cast up to a double and float values can be represented as a double. If your computation generates a float value to be logged then use FFastLog.

See Also:

https://www.javatips.net/api/Eisenkraut-master/src/main/java/de/sciss/eisenkraut/math/FastLog.java, http://www.icsi.berkeley.edu/pubs/techreports/TR-07-002.pdf

Field Summary
- Fields inherited from class micycle.peasygradients.utilities.fastLog.FastLog
  LN2, LN2F, N

Constructor Summary

Constructors
Constructor	Description
`DFastLog()`	Create a new natural logarithm calculation instance.
`DFastLog(double base, int n)`	Create a new logarithm calculation instance.
`DFastLog(int n)`	Create a new logarithm calculation instance.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`float`	`fastLog(double x)`	Calculate the logarithm to the base given in the constructor.
`float`	`fastLog(float x)`	Calculate the logarithm to the configured base.
`float`	`fastLog2(double x)`	Calculate the logarithm to base 2.
`float`	`fastLog2(float x)`	Calculate the logarithm to base 2.
`double`	`getBase()`	Gets the base.
`int`	`getN()`	Gets the number of most significant bits to keep from the mantissa, i.e.
`int`	`getQ()`	Gets the number of least signification bits to ignore from the mantissa of a double (52-bits).
`double`	`getScale()`	Gets the scale to convert from log2 to logB (the base given by `FastLog.getBase()`) by multiplication.
`float`	`log(double x)`	Calculate the logarithm to the configured base, handling special cases.
`float`	`log(float x)`	Calculate the logarithm to the configured base, handling special cases.
`float`	`log2(double x)`	Calculate the logarithm to base 2, handling special cases.
`float`	`log2(float x)`	Calculate the logarithm to base 2, handling special cases.

Methods inherited from class micycle.peasygradients.utilities.fastLog.FastLog
computeScale, exactLog2, fastLog2D, fastLogD, log2D, logD

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - DFastLog
```
public DFastLog()
```
    Create a new natural logarithm calculation instance.
  - DFastLog
```
public DFastLog(int n)
```
    Create a new logarithm calculation instance. This will hold the pre-calculated log values for base E and a table size depending on a given mantissa quantization.
    
    Parameters:
    
    n - The number of bits to keep from the mantissa. Table storage = 2^(n+1) * 4 bytes, e.g. 64Kb for n=13
  - DFastLog
```
public DFastLog(double base,
                int n)
```
    Create a new logarithm calculation instance. This will hold the pre-calculated log values for a given base and a table size depending on a given mantissa quantization.
    
    Parameters:
    
    base - the logarithm base (e.g. 2 for log duals, 10 for decibels calculations, Math.E for natural log)
    
    n - The number of bits to keep from the mantissa. Table storage = 2^(n+1) * 4 bytes, e.g. 64Kb for n=13
- Method Detail
  - getBase
```
public double getBase()
```
    Description copied from class: FastLog
    
    Gets the base.
    
    Specified by:
    
    getBase in class FastLog
    
    Returns:
    
    the base
  - getScale
```
public double getScale()
```
    Description copied from class: FastLog
    
    Gets the scale to convert from log2 to logB (the base given by FastLog.getBase()) by multiplication.
    
    Specified by:
    
    getScale in class FastLog
    
    Returns:
    
    the scale
  - getN
```
public int getN()
```
    Description copied from class: FastLog
    
    Gets the number of most significant bits to keep from the mantissa, i.e. the binary precision of the floating point number before computing the log.
    
    Specified by:
    
    getN in class FastLog
    
    Returns:
    
    the number of most significant bits to keep
  - getQ
```
public int getQ()
```
    Gets the number of least signification bits to ignore from the mantissa of a double (52-bits).
    
    Returns:
    
    the number of least signification bits to ignore
  - log2
```
public float log2(double x)
```
    Description copied from class: FastLog
    Calculate the logarithm to base 2, handling special cases.
    Special cases:
    
    If the argument is NaN or less than zero, then the result is NaN.
    If the argument is positive infinity, then the result is positive infinity.
    If the argument is positive zero or negative zero, then the result is negative infinity.
    Specified by:
    
    log2 in class FastLog
    
    Parameters:
    
    x - the argument
    
    Returns:
    
    log(x)
  - log2
```
public float log2(float x)
```
    Calculate the logarithm to base 2, handling special cases.
    Special cases:
    
    If the argument is NaN or less than zero, then the result is NaN.
    If the argument is positive infinity, then the result is positive infinity.
    If the argument is positive zero or negative zero, then the result is negative infinity.
    
    This just calls log2(double). Use FFastLog for a dedicated float version.
    Specified by:
    
    log2 in class FastLog
    
    Parameters:
    
    x - the argument
    
    Returns:
    
    log(x)
  - fastLog2
```
public float fastLog2(double x)
```
    Calculate the logarithm to base 2. Requires the argument be finite and positive.
    Special cases:
    
    If the argument is NaN, then the result is incorrect.
    If the argument is negative, then the result is incorrect (log(-x)).
    If the argument is positive infinity, then the result is incorrect (Math.log(Double.MAX_VALUE)).
    If the argument is positive zero or negative zero, then the result is negative infinity.
    Specified by:
    
    fastLog2 in class FastLog
    
    Parameters:
    
    x - the argument (must be strictly positive)
    
    Returns:
    
    log( x )
  - fastLog2
```
public float fastLog2(float x)
```
    Calculate the logarithm to base 2. Requires the argument be finite and strictly positive.
    Special cases:
    
    If the argument is NaN, then the result is incorrect.
    If the argument is negative, then the result is incorrect.
    If the argument is positive infinity, then the result is incorrect.
    If the argument is positive zero or negative zero, then the result is incorrect.
    
    Sub-classes may handle some of the special cases.
    This just calls fastLog2(double). Use FFastLog for a dedicated float version.
    Specified by:
    
    fastLog2 in class FastLog
    
    Parameters:
    
    x - the argument (must be strictly positive)
    
    Returns:
    
    log(x)
  - log
```
public float log(double x)
```
    Description copied from class: FastLog
    Calculate the logarithm to the configured base, handling special cases.
    Special cases:
    
    If the argument is NaN or less than zero, then the result is NaN.
    If the argument is positive infinity, then the result is positive infinity.
    If the argument is positive zero or negative zero, then the result is negative infinity.
    Specified by:
    
    log in class FastLog
    
    Parameters:
    
    x - the argument
    
    Returns:
    
    log(x)
    
    See Also:
    
    FastLog.getBase()
  - log
```
public float log(float x)
```
    Calculate the logarithm to the configured base, handling special cases.
    Special cases:
    
    If the argument is NaN or less than zero, then the result is NaN.
    If the argument is positive infinity, then the result is positive infinity.
    If the argument is positive zero or negative zero, then the result is negative infinity.
    
    This just calls log(double). Use FFastLog for a dedicated float version.
    Specified by:
    
    log in class FastLog
    
    Parameters:
    
    x - the argument
    
    Returns:
    
    log(x)
    
    See Also:
    
    FastLog.getBase()
  - fastLog
```
public float fastLog(double x)
```
    Calculate the logarithm to the base given in the constructor. Requires the argument be finite and positive.
    Special cases:
    
    If the argument is NaN, then the result is incorrect.
    If the argument is negative, then the result is incorrect (log(-x)).
    If the argument is positive infinity, then the result is incorrect (Math.log(Double.MAX_VALUE)).
    If the argument is positive zero or negative zero, then the result is negative infinity.
    Specified by:
    
    fastLog in class FastLog
    
    Parameters:
    
    x - the argument (must be strictly positive)
    
    Returns:
    
    log( x )
    
    See Also:
    
    FastLog.getBase()
  - fastLog
```
public float fastLog(float x)
```
    Calculate the logarithm to the configured base. Requires the argument be finite and strictly positive.
    Special cases:
    
    If the argument is NaN, then the result is incorrect.
    If the argument is negative, then the result is incorrect.
    If the argument is positive infinity, then the result is incorrect.
    If the argument is positive zero or negative zero, then the result is incorrect.
    
    Sub-classes may handle some of the special cases.
    This just calls fastLog(double). Use FFastLog for a dedicated float version.
    Specified by:
    
    fastLog in class FastLog
    
    Parameters:
    
    x - the argument (must be strictly positive)
    
    Returns:
    
    log(x)
    
    See Also:
    
    FastLog.getBase()

Class DFastLog

Field Summary

Fields inherited from class micycle.peasygradients.utilities.fastLog.FastLog

Constructor Summary

Method Summary

Methods inherited from class micycle.peasygradients.utilities.fastLog.FastLog

Methods inherited from class java.lang.Object

Constructor Detail

DFastLog

DFastLog

DFastLog

Method Detail

getBase

getScale

getN

getQ

log2

log2

fastLog2

fastLog2

log

log

fastLog

fastLog