date: 2018/05/06 01:19:57
- user: cg
- file: ComplexDoubleArray.st directory: libbasic2
- module: stx stc-classLibrary: libbasic2
- Claus Gittinger
ComplexDoubleArrays store complex numbers (in double prevision) and nothing else.
They have been added to support heavy duty number crunching and
data exchange with openGL frameworks and other mass data libraries
somewhat better than other smalltalks do.
Storing Complex numbers in these objects (instead of Arrays)
has some benefits:
1) since the values are stored directly (instead of pointers to them)
both access overhead and garbage collect overhead is minimized.
2) they can be much faster passed to c functions (such as graphics
libraries or heavy duty math packages), since the double values
come packed and can be used in C by using a (double *) or double.
There is no need to loop over the array extracting doubles.
3) they could (in theory) be much more easily be processed by things like
vector and array processors
Be aware however, that ComplexDoubleArrays are not supported in other
smalltalks - your program will thus become somewhat less portable.
(since their protocol is the same as normal arrays filled with floats,
they can of course be easily simulated - a bit slower though)
However, they could be simulated by a ByteArray, using doubleAt: and
doubleAtPut: messages to access the elements, but that seems a bit
clumsy and unelegant. Also, the stc-compiler may learn how to deal
with Float- and DoubleArrays, making accesses very fast in the future.
Hint: if you use doubleArrays in your application and must port it
to some other smalltalk, define a DoubleArray class there, which is derived
from ByteArray, and add access methods.
Of course, ComplexDoubleArrays can be subclassed,
and named instance variables can be added there.
OBJ-HEADER + (size * double-size * 2)
for bit-like containers, return the number of bytes stored per element.
Here, 2*8 is returned
at: index put: aComplex
at: index put: realPart i: imaginaryPart
return true, if I can hold this kind of object
vec := ComplexDoubleArray new:4.
vec at:1 put:(1 + 4i).
vec at:2 put:(2 + 4i).
vec at:4 put:(4 + 4i).