| 202 |
}\right) h(\vecf_x - i) |
}\right) h(\vecf_x - i) |
| 203 |
\end{displaymath}% |
\end{displaymath}% |
| 204 |
Thus, we see that the kernel $h$ is evaluated $2s$ times per axis (\ie{}, $6s$ times in 3D). |
Thus, we see that the kernel $h$ is evaluated $2s$ times per axis (\ie{}, $6s$ times in 3D). |
| 205 |
|
\figref{fig:3d-probe-code-c} gives C code for this operation. |
| 206 |
\begin{figure}[t] |
\begin{figure}[p] |
| 207 |
\begin{quote} |
\begin{quote} |
| 208 |
\lstset{language=C} |
\lstset{language=C} |
| 209 |
\begin{lstlisting} |
\begin{lstlisting} |
| 217 |
{ |
{ |
| 218 |
double nx, ny, nz, fx, fy, fz; |
double nx, ny, nz, fx, fy, fz; |
| 219 |
|
|
| 220 |
|
fx = modf (x[0], &nx); |
| 221 |
|
fy = modf (x[1], &ny); |
| 222 |
|
fz = modf (x[2], &nz); |
| 223 |
|
|
| 224 |
// compute kernel values for each axis |
// compute kernel values for each axis |
| 225 |
double hx[4], hy[4], hz[4]; |
double hx[4], hy[4], hz[4]; |
| 226 |
for (int k = 1-s; j < s; k++) { |
for (int i = 1-s; i < s; i++) { |
| 227 |
double t = fx - k; |
double t; |
| 228 |
hx[k+s-1] = h[s-k][0] + t*(h[s-k][1] + t*(h[s-k][2] + t*h[s-k][3])); |
t = fx - i; |
| 229 |
double t = fy - k; |
hx[i+s-1] = h[s-i][0] + t*(h[s-i][1] + t*(h[s-i][2] + t*h[s-i][3])); |
| 230 |
hy[k+s-1] = h[s-k][0] + t*(h[s-k][1] + t*(h[s-k][2] + t*h[s-k][3])); |
t = fy - i; |
| 231 |
double t = fz - k; |
hy[i+s-1] = h[s-i][0] + t*(h[s-i][1] + t*(h[s-i][2] + t*h[s-i][3])); |
| 232 |
hz[k+s-1] = h[s-k][0] + t*(h[s-k][1] + t*(h[s-k][2] + t*h[s-k][3])); |
t = fz - i; |
| 233 |
|
hz[i+s-1] = h[s-i][0] + t*(h[s-i][1] + t*(h[s-i][2] + t*h[s-i][3])); |
| 234 |
} |
} |
| 235 |
|
|
| 236 |
double vx = 0.0 |
double vx = 0.0 |
| 243 |
} |
} |
| 244 |
vy += vz * hy[j+s-1]; |
vy += vz * hy[j+s-1]; |
| 245 |
} |
} |
| 246 |
vx += vx * hy[i+s-1]; |
vx += vx * hx[i+s-1]; |
| 247 |
} |
} |
| 248 |
|
|
| 249 |
return vx; |
return vx; |
| 251 |
\end{lstlisting}% |
\end{lstlisting}% |
| 252 |
\end{quote}% |
\end{quote}% |
| 253 |
\caption{Computing $F\mkw{@}\vecx$ for a 3D scalar field in C} |
\caption{Computing $F\mkw{@}\vecx$ for a 3D scalar field in C} |
| 254 |
|
\label{fig:3d-probe-code-c} |
| 255 |
\end{figure} |
\end{figure} |
| 256 |
|
|
| 257 |
\section{Probing a 3D derivative field} |
\section{Probing a 3D derivative field} |
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