[Liboil] complex types?
ds at schleef.org
Mon Nov 14 18:54:51 PST 2005
On Mon, Nov 14, 2005 at 09:50:07AM +0100, Stephane Fillod wrote:
> On Sun, Nov 13, 2005 at 04:32:51PM -0800, David Schleef wrote:
> > Is there any reason to have complex integer types? I can understand
> > the need for complex float/double.
> Some applications do complex fixed-point (integer) computations.
> This is a lot faster on FPU-less systems.
Ah, sure. But then, liboil doesn't even have fixed-point types
currently. That would be nice to have.
> I mean 'float *' as in 'float *d_2xn' that has n interleaved real and
> imag float values. Speed can be one reason, existing data model of
> applications and/or hardware devices is another one.
> oil_sincos_f64()-like prototype does not fit my need, because "complex"
> args are not interleaved.
oil_sincos_interleaved_f64(double *d_2xn, double *s1_1, double *s2_1,
d_2xn[i*2 + 0] = cos(*s1_1 + *s2_1 * i);
d_2xn[i*2 + 1] = sin(*s1_1 + *s2_1 * i);
oil_complexmult_f64 (double *d_2xn, double *s1_2xn, double *s2_2xn, int
double a, b, c, d;
a = s1_2xn[2*i + 0];
b = s1_2xn[2*i + 1];
c = s2_2xn[2*i + 0];
d = s2_2xn[2*i + 1];
d_2xn[2*i + 0] = a * c - b * d;
d_2xn[2*i + 1] = a * d + b * c;
So in other words, complex would be a convention, not a new type,
somewhat like ARGB. BTW, I'm trying to avoid the issue in order to
take a wait-and-see approach.
> BTW, I don't understand why offset and interval
> are passed by address and not by value in oil_sincos_f64.
Everything is pass-by-address because it's about a million times
easier on the automatic testing and marshalling code. And that's
one of the reasons why liboil exists instead of being prototype
code in my random hacking directory.
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