DSP_autocor_rA8
DSP_autocor_rA8 AutoCorrelation
Function | void DSP_autocor_rA8(short * restrict r, const short * restrict x, int nx, int nr) | |
Arguments | r[nr] | Output array, Must be double word aligned. |
| x[nx+nr] | Input array. Must be |
| nx | Length of autocorrelation. Must be a multiple of 8. |
| nr | Number of lags. Must be a multiple of 4. |
Description | This routine accepts an input array of length nx + nr and performs nr | |
| autocorrelations each of length nx producing nr output results. This is typically | |
| used in VSELP code. | |
Algorithm | This is the C equivalent of the assembly code without restrictions. Note that | |
| the assembly code is hand optimized and restrictions may apply. | |
void DSP_autocor(short r[ ],short x[ ], int nx, int nr)
{
int i,k,sum;
for (i = 0; i < nr; i++){ sum = 0;
for (k = nr; k < nx+nr; k++) sum += x[k] * x[k−i];
r[i] = (sum >> 15);
}
}
Special Requirements
-nx must be a multiple of 8.
-nr must be a multiple of 4.
-x[ ] must be
-r[ ] must be
Implementation Notes
-Bank Conflicts: No bank conflicts occur.
-Interruptibility: The code is interruptible.
-The inner loop is unrolled 8 times.
-The outer loop is unrolled 4 times.
