Question: I have a problem that requires me to find the 9 biggest numbers out of 1024 16 bit numbers and I want to get an idea of how many cycles this will take.

Answer: The fastest way I've found to sort on the C54x uses the MAX or MIN instructions. You might start with something like the following which is similar to the "sub-block" position search I developed for QCELP:

1. Break the array into 16 blocks of 64 values:

a. Do outer loop 16 times (for each block)

b. Do inner loop 64 times (finds local max)

LD *AR+, A

MAX B ;can inline this inner loop to save branch cycles

c. Save local max

2. You now have 16 local maximums. Do a position search to find overall max and its position within the 16. Save the overall max result somewhere. The position will tell you which sub-block in the array of 1024 contains the global max. Then go to that sub-block and overwrite the max value with zero.

3. Repeat this 8 more times to find the next 8 highest values.

This should take about 9 * (2048 cycles for inlined array search + 100 cycles??

Overhead for each pass) => 19,332 cycles

It could probably be sped up as much as 40% by eliminating the sub-blocks with the 7 lowest local maximums from further consideration after the first pass. That would require copying the array into a new one of size 576.