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cosmolib.c
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Thu, Feb 20, 00:25

cosmolib.c
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#include <Python.h>
#include <math.h>
#include <numpy/arrayobject.h>
/*********************************/
/* Integration kernel for da */
/*********************************/
struct kernelparam
{
float Omega0;
float OmegaLambda;
float Hubble;
};
float kernel(float a, struct kernelparam param)
{
float h;
h = param.Omega0 / (a * a * a) + (1 - param.Omega0 - param.OmegaLambda) / (a * a) + param.OmegaLambda;
h = param.Hubble * sqrt(h);
return 1 / (h * a);
}
/*********************************/
/* some nr functions */
/*********************************/
#define FUNC(x,y) ((*func)(x,y))
float trapzd(float (*func)(float,struct kernelparam param), struct kernelparam param, float a, float b, int n)
{
float x,tnm,sum,del;
static float s;
int it,j;
if (n == 1) {
return (s=0.5*(b-a)*(FUNC(a,param)+FUNC(b,param)));
} else {
for (it=1,j=1;j<n-1;j++) it <<= 1;
tnm=it;
del=(b-a)/tnm;
x=a+0.5*del;
for (sum=0.0,j=1;j<=it;j++,x+=del) sum += FUNC(x,param);
s=0.5*(s+(b-a)*sum/tnm);
return s;
}
}
float qsimp(float (*func)(float,struct kernelparam param), struct kernelparam param, float a, float b, float eps, int jmax)
{
float trapzd(float (*func)(float,struct kernelparam param), struct kernelparam param, float a, float b, int n);
int j;
float s,st,ost=0.0,os=0.0;
for (j=1;j<=jmax;j++) {
st=trapzd(func,param,a,b,j);
s=(4.0*st-ost)/3.0;
if (j > 5)
if (fabs(s-os) < eps*fabs(os) ||
(s == 0.0 && os == 0.0)) return s;
os=s;
ost=st;
}
printf("Too many steps in routine qsimp\n");
return 0.0;
}
/*********************************/
/* Age_a */
/*********************************/
static PyObject *
cosmolib_Age_a(self, args)
PyObject *self;
PyObject *args;
{
PyArrayObject *as;
PyArrayObject *ts;
float Omega0,OmegaLambda,Hubble;
float a;
float t;
int i;
struct kernelparam param;
/* parse arguments */
if (!PyArg_ParseTuple(args, "Offf", &as,&Omega0,&OmegaLambda,&Hubble))
return NULL;
/* create output */
//ts = (PyArrayObject *) PyArray_FromDims(as->nd,as->dimensions,as->descr->type_num);
ts = (PyArrayObject *) PyArray_SimpleNew(as->nd,as->dimensions,as->descr->type_num);
/* param */
param.Omega0 = Omega0;
param.OmegaLambda = OmegaLambda;
param.Hubble = Hubble;
for (i = 0; i < as->dimensions[0]; i++)
{
a = *(double *)(as->data + i*(as->strides[0]));
if (a<1e-6)
a = 1e-6;
t = qsimp(kernel,param,(float)a,(float)1., 1e-6, 100);
*(double *)(ts->data + i*(ts->strides[0])) = t;
}
return PyArray_Return(ts);
}
/* definition of the method table */
static PyMethodDef cosmolibMethods[] = {
{"Age_a", cosmolib_Age_a, METH_VARARGS,
"Return age of the univers as a function of a (expansion factor)."},
{NULL, NULL, 0, NULL} /* Sentinel */
};
void initcosmolib(void)
{
(void) Py_InitModule("cosmolib", cosmolibMethods);
import_array();
}

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