I have used the following code to get the cpu frequency .
-(int) returnCPUFreq
{
size_t length;
int mib[6];
int result;
mib[0] = CTL_HW;
mib[1] = HW_CPU_FREQ;
length = sizeof(result);
sysctl(mib, 2, &result, &length, NULL, 0);
return result;
}
It is giving the 6 digits code and it is varying for every time when I run the app . i.e the output is first time 644311 , second time 303921 .....
Is this code correct ? Is the values vary for everytime when I run the app?
Your answer is correct. You could check wether sysctl return no error by checking sysctl(mib, 2, &result, &length, NULL, 0) < 0
But this won't change anything in the varying frequency. This is because Apple doesn't allow reading the frequency for all of their products.
When you need it to determine how many details or something like that you can enable I would check on the hardware model and look up the cpu frequency in an nsdictionary where i placed all the available hardware models.
Related
It is my first attempt to implement recursion with CUDA. The goal is to extract all the combinations from a set of chars "12345" using the power of CUDA to parallelize dynamically the task. Here is my kernel:
__device__ char route[31] = { "_________________________"};
__device__ char init[6] = { "12345" };
__global__ void Recursive(int depth) {
// up to depth 6
if (depth == 5) return;
// newroute = route - idx
int x = depth * 6;
printf("%s\n", route);
int o = 0;
int newlen = 0;
for (int i = 0; i<6; ++i)
{
if (i != threadIdx.x)
{
route[i+x-o] = init[i];
newlen++;
}
else
{
o = 1;
}
}
Recursive<<<1,newlen>>>(depth + 1);
}
__global__ void RecursiveCount() {
Recursive <<<1,5>>>(0);
}
The idea is to exclude 1 item (the item corresponding to the threadIdx) in each different thread. In each recursive call, using the variable depth, it works over a different base (variable x) on the route device variable.
I expect the kernel prompts something like:
2345_____________________
1345_____________________
1245_____________________
1234_____________________
2345_345_________________
2345_245_________________
2345_234_________________
2345_345__45_____________
2345_345__35_____________
2345_345__34_____________
..
2345_245__45_____________
..
But it prompts ...
·_____________
·_____________
·_____________
·_____________
·_____________
·2345
·2345
·2345
·2345
...
What I´m doing wrong?
What I´m doing wrong?
I may not articulate every problem with your code, but these items should get you a lot closer.
I recommend providing a complete example. In my view it is basically required by Stack Overflow, see item 1 here, note use of the word "must". Your example is missing any host code, including the original kernel call. It's only a few extra lines of code, why not include it? Sure, in this case, I can deduce what the call must have been, but why not just include it? Anyway, based on the output you indicated, it seems fairly evident the launch configuration of the host launch would have to be <<<1,1>>>.
This doesn't seem to be logical to me:
I expect the kernel prompts something like:
2345_____________________
The very first thing your kernel does is print out the route variable, before making any changes to it, so I would expect _____________________. However we can "fix" this by moving the printout to the end of the kernel.
You may be confused about what a __device__ variable is. It is a global variable, and there is only one copy of it. Therefore, when you modify it in your kernel code, every thread, in every kernel, is attempting to modify the same global variable, at the same time. That cannot possibly have orderly results, in any thread-parallel environment. I chose to "fix" this by making a local copy for each thread to work on.
You have an off-by-1 error, as well as an extent error in this loop:
for (int i = 0; i<6; ++i)
The off-by-1 error is due to the fact that you are iterating over 6 possible items (that is, i can reach a value of 5) but there are only 5 items in your init variable (the 6th item being a null terminator. The correct indexing starts out over 0-4 (with one of those being skipped). On subsequent iteration depths, its necessary to reduce this indexing extent by 1. Note that I've chosen to fix the first error here by increasing the length of init. There are other ways to fix, of course. My method inserts an extra _ between depths in the result.
You assume that at each iteration depth, the correct choice of items is the same, and in the same order, i.e. init. However this is not the case. At each depth, the choices of items must be selected not from the unchanging init variable, but from the choices passed from previous depth. Therefore we need a local, per-thread copy of init also.
A few other comments about CUDA Dynamic Parallelism (CDP). When passing pointers to data from one kernel scope to a child scope, local space pointers cannot be used. Therefore I allocate for the local copy of route from the heap, so it can be passed to child kernels. init can be deduced from route, so we can use an ordinary local variable for myinit.
You're going to quickly hit some dynamic parallelism (and perhaps memory) limits here if you continue this. I believe the total number of kernel launches for this is 5^5, which is 3125 (I'm doing this quickly, I may be mistaken). CDP has a pending launch limit of 2000 kernels by default. We're not hitting this here according to what I see, but you'll run into that sooner or later if you increase the depth or width of this operation. Furthermore, in-kernel allocations from the device heap are by default limited to 8KB. I don't seem to be hitting that limit, but probably I am, so my design should probably be modified to fix that.
Finally, in-kernel printf output is limited to the size of a particular buffer. If this technique is not already hitting that limit, it will soon if you increase the width or depth.
Here is a worked example, attempting to address the various items above. I'm not claiming it is defect free, but I think the output is closer to your expectations. Note that due to character limits on SO answers, I've truncated/excerpted some of the output.
$ cat t1639.cu
#include <stdio.h>
__device__ char route[31] = { "_________________________"};
__device__ char init[7] = { "12345_" };
__global__ void Recursive(int depth, const char *oroute) {
char *nroute = (char *)malloc(31);
char myinit[7];
if (depth == 0) memcpy(myinit, init, 6);
else memcpy(myinit, oroute+(depth-1)*6, 6);
myinit[6] = 0;
if (nroute == NULL) {printf("oops\n"); return;}
memcpy(nroute, oroute, 30);
nroute[30] = 0;
// up to depth 6
if (depth == 5) return;
// newroute = route - idx
int x = depth * 6;
//printf("%s\n", nroute);
int o = 0;
int newlen = 0;
for (int i = 0; i<(6-depth); ++i)
{
if (i != threadIdx.x)
{
nroute[i+x-o] = myinit[i];
newlen++;
}
else
{
o = 1;
}
}
printf("%s\n", nroute);
Recursive<<<1,newlen>>>(depth + 1, nroute);
}
__global__ void RecursiveCount() {
Recursive <<<1,5>>>(0, route);
}
int main(){
RecursiveCount<<<1,1>>>();
cudaDeviceSynchronize();
}
$ nvcc -o t1639 t1639.cu -rdc=true -lcudadevrt -arch=sm_70
$ cuda-memcheck ./t1639
========= CUDA-MEMCHECK
2345_____________________
1345_____________________
1245_____________________
1235_____________________
1234_____________________
2345__345________________
2345__245________________
2345__235________________
2345__234________________
2345__2345_______________
2345__345___45___________
2345__345___35___________
2345__345___34___________
2345__345___345__________
2345__345___45____5______
2345__345___45____4______
2345__345___45____45_____
2345__345___45____5______
2345__345___45____5_____5
2345__345___45____4______
2345__345___45____4_____4
2345__345___45____45____5
2345__345___45____45____4
2345__345___35____5______
2345__345___35____3______
2345__345___35____35_____
2345__345___35____5______
2345__345___35____5_____5
2345__345___35____3______
2345__345___35____3_____3
2345__345___35____35____5
2345__345___35____35____3
2345__345___34____4______
2345__345___34____3______
2345__345___34____34_____
2345__345___34____4______
2345__345___34____4_____4
2345__345___34____3______
2345__345___34____3_____3
2345__345___34____34____4
2345__345___34____34____3
2345__345___345___45_____
2345__345___345___35_____
2345__345___345___34_____
2345__345___345___45____5
2345__345___345___45____4
2345__345___345___35____5
2345__345___345___35____3
2345__345___345___34____4
2345__345___345___34____3
2345__245___45___________
2345__245___25___________
2345__245___24___________
2345__245___245__________
2345__245___45____5______
2345__245___45____4______
2345__245___45____45_____
2345__245___45____5______
2345__245___45____5_____5
2345__245___45____4______
2345__245___45____4_____4
2345__245___45____45____5
2345__245___45____45____4
2345__245___25____5______
2345__245___25____2______
2345__245___25____25_____
2345__245___25____5______
2345__245___25____5_____5
2345__245___25____2______
2345__245___25____2_____2
2345__245___25____25____5
2345__245___25____25____2
2345__245___24____4______
2345__245___24____2______
2345__245___24____24_____
2345__245___24____4______
2345__245___24____4_____4
2345__245___24____2______
2345__245___24____2_____2
2345__245___24____24____4
2345__245___24____24____2
2345__245___245___45_____
2345__245___245___25_____
2345__245___245___24_____
2345__245___245___45____5
2345__245___245___45____4
2345__245___245___25____5
2345__245___245___25____2
2345__245___245___24____4
2345__245___245___24____2
2345__235___35___________
2345__235___25___________
2345__235___23___________
2345__235___235__________
2345__235___35____5______
2345__235___35____3______
2345__235___35____35_____
2345__235___35____5______
2345__235___35____5_____5
2345__235___35____3______
2345__235___35____3_____3
2345__235___35____35____5
2345__235___35____35____3
2345__235___25____5______
2345__235___25____2______
2345__235___25____25_____
2345__235___25____5______
2345__235___25____5_____5
2345__235___25____2______
2345__235___25____2_____2
2345__235___25____25____5
2345__235___25____25____2
2345__235___23____3______
2345__235___23____2______
2345__235___23____23_____
2345__235___23____3______
2345__235___23____3_____3
2345__235___23____2______
2345__235___23____2_____2
2345__235___23____23____3
2345__235___23____23____2
2345__235___235___35_____
2345__235___235___25_____
2345__235___235___23_____
2345__235___235___35____5
2345__235___235___35____3
2345__235___235___25____5
2345__235___235___25____2
2345__235___235___23____3
2345__235___235___23____2
2345__234___34___________
2345__234___24___________
2345__234___23___________
2345__234___234__________
2345__234___34____4______
2345__234___34____3______
2345__234___34____34_____
2345__234___34____4______
2345__234___34____4_____4
2345__234___34____3______
2345__234___34____3_____3
2345__234___34____34____4
2345__234___34____34____3
2345__234___24____4______
2345__234___24____2______
2345__234___24____24_____
2345__234___24____4______
2345__234___24____4_____4
2345__234___24____2______
2345__234___24____2_____2
2345__234___24____24____4
2345__234___24____24____2
2345__234___23____3______
2345__234___23____2______
2345__234___23____23_____
2345__234___23____3______
2345__234___23____3_____3
2345__234___23____2______
2345__234___23____2_____2
2345__234___23____23____3
2345__234___23____23____2
2345__234___234___34_____
2345__234___234___24_____
2345__234___234___23_____
2345__234___234___34____4
2345__234___234___34____3
2345__234___234___24____4
2345__234___234___24____2
2345__234___234___23____3
2345__234___234___23____2
2345__2345__345__________
2345__2345__245__________
2345__2345__235__________
2345__2345__234__________
2345__2345__345___45_____
2345__2345__345___35_____
2345__2345__345___34_____
2345__2345__345___45____5
2345__2345__345___45____4
2345__2345__345___35____5
2345__2345__345___35____3
2345__2345__345___34____4
2345__2345__345___34____3
2345__2345__245___45_____
2345__2345__245___25_____
2345__2345__245___24_____
2345__2345__245___45____5
2345__2345__245___45____4
2345__2345__245___25____5
2345__2345__245___25____2
2345__2345__245___24____4
2345__2345__245___24____2
2345__2345__235___35_____
2345__2345__235___25_____
2345__2345__235___23_____
2345__2345__235___35____5
2345__2345__235___35____3
2345__2345__235___25____5
2345__2345__235___25____2
2345__2345__235___23____3
2345__2345__235___23____2
2345__2345__234___34_____
2345__2345__234___24_____
2345__2345__234___23_____
2345__2345__234___34____4
2345__2345__234___34____3
2345__2345__234___24____4
2345__2345__234___24____2
2345__2345__234___23____3
2345__2345__234___23____2
1345__345________________
1345__145________________
1345__135________________
1345__134________________
1345__1345_______________
1345__345___45___________
1345__345___35___________
1345__345___34___________
1345__345___345__________
1345__345___45____5______
1345__345___45____4______
1345__345___45____45_____
1345__345___45____5______
1345__345___45____5_____5
1345__345___45____4______
1345__345___45____4_____4
1345__345___45____45____5
1345__345___45____45____4
1345__345___35____5______
1345__345___35____3______
1345__345___35____35_____
1345__345___35____5______
1345__345___35____5_____5
1345__345___35____3______
1345__345___35____3_____3
1345__345___35____35____5
1345__345___35____35____3
1345__345___34____4______
1345__345___34____3______
1345__345___34____34_____
1345__345___34____4______
1345__345___34____4_____4
1345__345___34____3______
1345__345___34____3_____3
1345__345___34____34____4
1345__345___34____34____3
1345__345___345___45_____
1345__345___345___35_____
1345__345___345___34_____
1345__345___345___45____5
1345__345___345___45____4
1345__345___345___35____5
1345__345___345___35____3
1345__345___345___34____4
1345__345___345___34____3
1345__145___45___________
1345__145___15___________
1345__145___14___________
1345__145___145__________
1345__145___45____5______
1345__145___45____4______
1345__145___45____45_____
1345__145___45____5______
1345__145___45____5_____5
1345__145___45____4______
1345__145___45____4_____4
1345__145___45____45____5
1345__145___45____45____4
1345__145___15____5______
1345__145___15____1______
1345__145___15____15_____
1345__145___15____5______
1345__145___15____5_____5
1345__145___15____1______
1345__145___15____1_____1
1345__145___15____15____5
1345__145___15____15____1
1345__145___14____4______
1345__145___14____1______
1345__145___14____14_____
1345__145___14____4______
1345__145___14____4_____4
1345__145___14____1______
1345__145___14____1_____1
1345__145___14____14____4
1345__145___14____14____1
1345__145___145___45_____
1345__145___145___15_____
1345__145___145___14_____
1345__145___145___45____5
1345__145___145___45____4
1345__145___145___15____5
1345__145___145___15____1
1345__145___145___14____4
1345__145___145___14____1
1345__135___35___________
1345__135___15___________
1345__135___13___________
1345__135___135__________
1345__135___35____5______
1345__135___35____3______
1345__135___35____35_____
1345__135___35____5______
1345__135___35____5_____5
1345__135___35____3______
1345__135___35____3_____3
1345__135___35____35____5
1345__135___35____35____3
1345__135___15____5______
1345__135___15____1______
1345__135___15____15_____
1345__135___15____5______
1345__135___15____5_____5
1345__135___15____1______
1345__135___15____1_____1
1345__135___15____15____5
1345__135___15____15____1
1345__135___13____3______
1345__135___13____1______
1345__135___13____13_____
1345__135___13____3______
1345__135___13____3_____3
1345__135___13____1______
1345__135___13____1_____1
1345__135___13____13____3
1345__135___13____13____1
1345__135___135___35_____
1345__135___135___15_____
1345__135___135___13_____
1345__135___135___35____5
1345__135___135___35____3
1345__135___135___15____5
1345__135___135___15____1
1345__135___135___13____3
1345__135___135___13____1
1345__134___34___________
1345__134___14___________
1345__134___13___________
1345__134___134__________
1345__134___34____4______
1345__134___34____3______
1345__134___34____34_____
1345__134___34____4______
1345__134___34____4_____4
1345__134___34____3______
1345__134___34____3_____3
1345__134___34____34____4
1345__134___34____34____3
1345__134___14____4______
1345__134___14____1______
1345__134___14____14_____
1345__134___14____4______
1345__134___14____4_____4
1345__134___14____1______
1345__134___14____1_____1
1345__134___14____14____4
1345__134___14____14____1
1345__134___13____3______
1345__134___13____1______
1345__134___13____13_____
1345__134___13____3______
1345__134___13____3_____3
1345__134___13____1______
1345__134___13____1_____1
1345__134___13____13____3
1345__134___13____13____1
1345__134___134___34_____
1345__134___134___14_____
1345__134___134___13_____
1345__134___134___34____4
1345__134___134___34____3
1345__134___134___14____4
1345__134___134___14____1
1345__134___134___13____3
1345__134___134___13____1
1345__1345__345__________
1345__1345__145__________
1345__1345__135__________
1345__1345__134__________
1345__1345__345___45_____
1345__1345__345___35_____
1345__1345__345___34_____
1345__1345__345___45____5
1345__1345__345___45____4
1345__1345__345___35____5
1345__1345__345___35____3
1345__1345__345___34____4
1345__1345__345___34____3
1345__1345__145___45_____
1345__1345__145___15_____
1345__1345__145___14_____
1345__1345__145___45____5
1345__1345__145___45____4
1345__1345__145___15____5
1345__1345__145___15____1
1345__1345__145___14____4
1345__1345__145___14____1
1345__1345__135___35_____
1345__1345__135___15_____
1345__1345__135___13_____
1345__1345__135___35____5
1345__1345__135___35____3
1345__1345__135___15____5
1345__1345__135___15____1
1345__1345__135___13____3
1345__1345__135___13____1
1345__1345__134___34_____
1345__1345__134___14_____
1345__1345__134___13_____
1345__1345__134___34____4
1345__1345__134___34____3
1345__1345__134___14____4
1345__1345__134___14____1
1345__1345__134___13____3
1345__1345__134___13____1
1245__245________________
1245__145________________
1245__125________________
1245__124________________
1245__1245_______________
1245__245___45___________
1245__245___25___________
1245__245___24___________
1245__245___245__________
1245__245___45____5______
1245__245___45____4______
1245__245___45____45_____
1245__245___45____5______
1245__245___45____5_____5
1245__245___45____4______
1245__245___45____4_____4
1245__245___45____45____5
1245__245___45____45____4
1245__245___25____5______
1245__245___25____2______
1245__245___25____25_____
1245__245___25____5______
1245__245___25____5_____5
1245__245___25____2______
1245__245___25____2_____2
1245__245___25____25____5
1245__245___25____25____2
1245__245___24____4______
1245__245___24____2______
1245__245___24____24_____
1245__245___24____4______
1245__245___24____4_____4
1245__245___24____2______
1245__245___24____2_____2
1245__245___24____24____4
1245__245___24____24____2
1245__245___245___45_____
1245__245___245___25_____
1245__245___245___24_____
1245__245___245___45____5
1245__245___245___45____4
1245__245___245___25____5
1245__245___245___25____2
1245__245___245___24____4
1245__245___245___24____2
1245__145___45___________
1245__145___15___________
1245__145___14___________
1245__145___145__________
1245__145___45____5______
1245__145___45____4______
1245__145___45____45_____
1245__145___45____5______
1245__145___45____5_____5
1245__145___45____4______
...
1235__1235__235___25_____
1235__1235__235___23_____
1235__1235__235___35____5
1235__1235__235___35____3
1235__1235__235___25____5
1235__1235__235___25____2
1235__1235__235___23____3
1235__1235__235___23____2
1235__1235__135___35_____
1235__1235__135___15_____
1235__1235__135___13_____
1235__1235__135___35____5
1235__1235__135___35____3
1235__1235__135___15____5
1235__1235__135___15____1
1235__1235__135___13____3
1235__1235__135___13____1
1235__1235__125___25_____
1235__1235__125___15_____
1235__1235__125___12_____
1235__1235__125___25____5
1235__1235__125___25____2
1235__1235__125___15____5
1235__1235__125___15____1
1235__1235__125___12____2
1235__1235__125___12____1
1235__1235__123___23_____
1235__1235__123___13_____
1235__1235__123___12_____
1235__1235__123___23____3
1235__1235__123___23____2
1235__1235__123___13____3
1235__1235__123___13____1
1235__1235__123___12____2
1235__1235__123___12____1
1234__234________________
1234__134________________
1234__124________________
1234__123________________
1234__1234_______________
1234__234___34___________
1234__234___24___________
1234__234___23___________
1234__234___234__________
1234__234___34____4______
1234__234___34____3______
1234__234___34____34_____
1234__234___34____4______
1234__234___34____4_____4
1234__234___34____3______
1234__234___34____3_____3
1234__234___34____34____4
1234__234___34____34____3
1234__234___24____4______
1234__234___24____2______
1234__234___24____24_____
1234__234___24____4______
1234__234___24____4_____4
1234__234___24____2______
1234__234___24____2_____2
1234__234___24____24____4
1234__234___24____24____2
1234__234___23____3______
1234__234___23____2______
1234__234___23____23_____
1234__234___23____3______
1234__234___23____3_____3
1234__234___23____2______
1234__234___23____2_____2
1234__234___23____23____3
1234__234___23____23____2
1234__234___234___34_____
1234__234___234___24_____
1234__234___234___23_____
1234__234___234___34____4
1234__234___234___34____3
1234__234___234___24____4
1234__234___234___24____2
1234__234___234___23____3
1234__234___234___23____2
1234__134___34___________
1234__134___14___________
1234__134___13___________
1234__134___134__________
1234__134___34____4______
1234__134___34____3______
1234__134___34____34_____
1234__134___34____4______
1234__134___34____4_____4
1234__134___34____3______
1234__134___34____3_____3
1234__134___34____34____4
1234__134___34____34____3
1234__134___14____4______
1234__134___14____1______
1234__134___14____14_____
1234__134___14____4______
1234__134___14____4_____4
1234__134___14____1______
1234__134___14____1_____1
1234__134___14____14____4
1234__134___14____14____1
1234__134___13____3______
1234__134___13____1______
1234__134___13____13_____
1234__134___13____3______
1234__134___13____3_____3
1234__134___13____1______
1234__134___13____1_____1
1234__134___13____13____3
1234__134___13____13____1
1234__134___134___34_____
1234__134___134___14_____
1234__134___134___13_____
1234__134___134___34____4
1234__134___134___34____3
1234__134___134___14____4
1234__134___134___14____1
1234__134___134___13____3
1234__134___134___13____1
1234__124___24___________
1234__124___14___________
1234__124___12___________
1234__124___124__________
1234__124___24____4______
1234__124___24____2______
1234__124___24____24_____
1234__124___24____4______
1234__124___24____4_____4
1234__124___24____2______
1234__124___24____2_____2
1234__124___24____24____4
1234__124___24____24____2
1234__124___14____4______
1234__124___14____1______
1234__124___14____14_____
1234__124___14____4______
1234__124___14____4_____4
1234__124___14____1______
1234__124___14____1_____1
1234__124___14____14____4
1234__124___14____14____1
1234__124___12____2______
1234__124___12____1______
1234__124___12____12_____
1234__124___12____2______
1234__124___12____2_____2
1234__124___12____1______
1234__124___12____1_____1
1234__124___12____12____2
1234__124___12____12____1
1234__124___124___24_____
1234__124___124___14_____
1234__124___124___12_____
1234__124___124___24____4
1234__124___124___24____2
1234__124___124___14____4
1234__124___124___14____1
1234__124___124___12____2
1234__124___124___12____1
1234__123___23___________
1234__123___13___________
1234__123___12___________
1234__123___123__________
1234__123___23____3______
1234__123___23____2______
1234__123___23____23_____
1234__123___23____3______
1234__123___23____3_____3
1234__123___23____2______
1234__123___23____2_____2
1234__123___23____23____3
1234__123___23____23____2
1234__123___13____3______
1234__123___13____1______
1234__123___13____13_____
1234__123___13____3______
1234__123___13____3_____3
1234__123___13____1______
1234__123___13____1_____1
1234__123___13____13____3
1234__123___13____13____1
1234__123___12____2______
1234__123___12____1______
1234__123___12____12_____
1234__123___12____2______
1234__123___12____2_____2
1234__123___12____1______
1234__123___12____1_____1
1234__123___12____12____2
1234__123___12____12____1
1234__123___123___23_____
1234__123___123___13_____
1234__123___123___12_____
1234__123___123___23____3
1234__123___123___23____2
1234__123___123___13____3
1234__123___123___13____1
1234__123___123___12____2
1234__123___123___12____1
1234__1234__234__________
1234__1234__134__________
1234__1234__124__________
1234__1234__123__________
1234__1234__234___34_____
1234__1234__234___24_____
1234__1234__234___23_____
1234__1234__234___34____4
1234__1234__234___34____3
1234__1234__234___24____4
1234__1234__234___24____2
1234__1234__234___23____3
1234__1234__234___23____2
1234__1234__134___34_____
1234__1234__134___14_____
1234__1234__134___13_____
1234__1234__134___34____4
1234__1234__134___34____3
1234__1234__134___14____4
1234__1234__134___14____1
1234__1234__134___13____3
1234__1234__134___13____1
1234__1234__124___24_____
1234__1234__124___14_____
1234__1234__124___12_____
1234__1234__124___24____4
1234__1234__124___24____2
1234__1234__124___14____4
1234__1234__124___14____1
1234__1234__124___12____2
1234__1234__124___12____1
1234__1234__123___23_____
1234__1234__123___13_____
1234__1234__123___12_____
1234__1234__123___23____3
1234__1234__123___23____2
1234__1234__123___13____3
1234__1234__123___13____1
1234__1234__123___12____2
1234__1234__123___12____1
========= ERROR SUMMARY: 0 errors
$
The answer given by Robert Crovella is correct at the 5th point, the mistake was in the using of init in every recursive call, but I want to clarify something that can be useful for other beginners with CUDA.
I used this variable because when I tried to launch a child kernel passing a local variable I always got the exception: Error: a pointer to local memory cannot be passed to a launch as an argument.
As I´m C# expert developer I´m not used to using pointers (Ref does the low-level-work for that) so I thought there was no way to do it in CUDA/c programming.
As Robert shows in its code it is possible copying the pointer with memalloc for using it as a referable argument.
Here is a kernel simplified as an example of deep recursion.
__device__ char init[6] = { "12345" };
__global__ void Recursive(int depth, const char* route) {
// up to depth 6
if (depth == 5) return;
//declaration for a referable argument (point 6)
char* newroute = (char*)malloc(6);
memcpy(newroute, route, 5);
int o = 0;
int newlen = 0;
for (int i = 0; i < (6 - depth); ++i)
{
if (i != threadIdx.x)
{
newroute[i - o] = route[i];
newlen++;
}
else
{
o = 1;
}
}
printf("%s\n", newroute);
Recursive <<<1, newlen>>>(depth + 1, newroute);
}
__global__ void RecursiveCount() {
Recursive <<<1, 5>>>(0, init);
}
I don't add the main call because I´m using ManagedCUDA for C# but as Robert says it can be figured-out how the call RecursiveCount is.
About ending arrays of char with /0 ... sorry but I don't know exactly what is the benefit; this code works fine without them.
I am using the SoXR library's variable rate feature to dynamically change the sampling rate of an audio stream in real time. Unfortunately I have have noticed that an unwanted clicking noise is present when changing the rate from 1.0 to a larger value (ex: 1.01) when testing with a sine wave. I have not noticed any unwanted artifacts when changing from a value larger than 1.0 to 1.0. I looked at the wave form it was producing and it appeared as if a few samples right at rate change are transposed incorrectly.
Here's a picture of an example of a stereo 440Hz sinewave stored using signed 16bit interleaved samples:
I also was unable to find any documentation covering the variable rate feature beyond the fifth code example. Here's is my initialization code:
bool DynamicRateAudioFrameQueue::intialize(uint32_t sampleRate, uint32_t numChannels)
{
mSampleRate = sampleRate;
mNumChannels = numChannels;
mRate = 1.0;
mGlideTimeInMs = 0;
// Intialize buffer
size_t intialBufferSize = 100 * sampleRate * numChannels / 1000; // 100 ms
pFifoSampleBuffer = new FiFoBuffer<int16_t>(intialBufferSize);
soxr_error_t error;
// Use signed int16 with interleaved channels
soxr_io_spec_t ioSpec = soxr_io_spec(SOXR_INT16_I, SOXR_INT16_I);
// "When creating a var-rate resampler, q_spec must be set as follows:" - example code
// Using SOXR_VR makes sense, but I'm not sure if the quality can be altered when using var-rate
soxr_quality_spec_t qualitySpec = soxr_quality_spec(SOXR_HQ, SOXR_VR);
// Using the var-rate io-spec is undocumented beyond a single code example which states
// "The ratio of the given input rate and ouput rates must equate to the
// maximum I/O ratio that will be used: "
// My tests show this is not true
double inRate = 1.0;
double outRate = 1.0;
mSoxrHandle = soxr_create(inRate, outRate, mNumChannels, &error, &ioSpec, &qualitySpec, NULL);
if (error == 0) // soxr_error_t == 0; no error
{
mIntialized = true;
return true;
}
else
{
return false;
}
}
Any idea what may be causing this to happen? Or have a suggestion for an alternative library that is capable of variable rate audio resampling in real time?
After speaking with the developer of the SoXR library I was able to resolve this issue by adjusting the maximum ratio parameters in the soxr_create method call. The developer's response can be found here.
I've been playing around with CoreBluetooth a lot lately, and although I can connect to some devices, I never seem to be able to properly read the data (characteristic values).
Right now I am connecting with the Wahoo BT Heartrate monitor, and I am getting all the signals but I can't make the data into anything sensible. (Yes, I am aware there is an API, but I am trying to connect without it, to properly get something working with CoreBluetooth).
I have so far not been able to turn the NSData (characteristic.value) into anything sensible. If you have any suggestions on how to make sense of this data that would be very much apreciated.
Below some code to fully parse all the HeartRate measurement characteristic data.
How to process the data depends on several things:
is the BPM written into a single byte or two?
is there EE data present?
calculate the number of RR-interval values, as there can be multiple values within in one message (I have seen up to three).
Here is the actual spec of the Heart_rate_measurement characteristic
// Instance method to get the heart rate BPM information
- (void) getHeartBPMData:(CBCharacteristic *)characteristic error:(NSError *)error
{
// Get the BPM //
// https://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.heart_rate_measurement.xml //
// Convert the contents of the characteristic value to a data-object //
NSData *data = [characteristic value];
// Get the byte sequence of the data-object //
const uint8_t *reportData = [data bytes];
// Initialise the offset variable //
NSUInteger offset = 1;
// Initialise the bpm variable //
uint16_t bpm = 0;
// Next, obtain the first byte at index 0 in the array as defined by reportData[0] and mask out all but the 1st bit //
// The result returned will either be 0, which means that the 2nd bit is not set, or 1 if it is set //
// If the 2nd bit is not set, retrieve the BPM value at the second byte location at index 1 in the array //
if ((reportData[0] & 0x01) == 0) {
// Retrieve the BPM value for the Heart Rate Monitor
bpm = reportData[1];
offset = offset + 1; // Plus 1 byte //
}
else {
// If the second bit is set, retrieve the BPM value at second byte location at index 1 in the array and //
// convert this to a 16-bit value based on the host’s native byte order //
bpm = CFSwapInt16LittleToHost(*(uint16_t *)(&reportData[1]));
offset = offset + 2; // Plus 2 bytes //
}
NSLog(#"bpm: %i", bpm);
// Determine if EE data is present //
// If the 3rd bit of the first byte is 1 this means there is EE data //
// If so, increase offset with 2 bytes //
if ((reportData[0] & 0x03) == 1) {
offset = offset + 2; // Plus 2 bytes //
}
// Determine if RR-interval data is present //
// If the 4th bit of the first byte is 1 this means there is RR data //
if ((reportData[0] & 0x04) == 0)
{
NSLog(#"%#", #"Data are not present");
}
else
{
// The number of RR-interval values is total bytes left / 2 (size of uint16) //
NSUInteger length = [data length];
NSUInteger count = (length - offset)/2;
NSLog(#"RR count: %lu", (unsigned long)count);
for (int i = 0; i < count; i++) {
// The unit for RR interval is 1/1024 seconds //
uint16_t value = CFSwapInt16LittleToHost(*(uint16_t *)(&reportData[offset]));
value = ((double)value / 1024.0 ) * 1000.0;
offset = offset + 2; // Plus 2 bytes //
NSLog(#"RR value %lu: %u", (unsigned long)i, value);
}
}
}
Well, you should be implementing the Heart Rate Profile (see here), which uses the Heart Rate Service. If you look at the Heart Rate Service Specifications, you will see that the format of the Heart Rate Measurement Characteristic changes according to the flags set in the least significant octet of the data packet.
This means that you need to set up your code to handle dynamic packet sizes.
So your general process would be:
Get the first byte of the value property and check it for:
Is the heart rate measurement 8 bits or 16 bits?
Is sensor contact supported?
Is sensor contact detected?
Is Energy Expended supported?
Is RR-Interval measurement supported?
If the heart rate measurement is 8 bits (bit 0 of byte 0 is 0), then cast the next byte into its intended format (hint: it's uint8_t). If it is 16 bits (i.e. bit 0 of byte 0 is 1), then cast the next two bytes into uint16_t.
If Energy Expended is supported (bit 3 of byte 0 is 1), then cast the next byte into a uint16_t.
Do the same with RR-Intervals.
Using NSData - especially with Core Bluetooth - takes some getting used to, but it's not that bad once you grasp the concept.
Good luck!
Well...
What you'll have to do, when you read the value for the characteric :
NSData *data = [characteritic value];
theTypeOfTheData value;
[data getByte:&value lenght:sizeof(value)];
But, theTypeOfTheData can be whatever has thought the developer of the device. So it could be UInt8, UInt16, or struct (with or without bitfield)... You'll have to get info by contacting the developer of the device or looking if there is some documentation.
For example, with my colleague, we use the the type of data that consumes the less space (because the device hasn't infinite memory) according to what is need.
Look into the descriptor of the characteristic. It may points out the type of data.
OSStatus SetupBuffers(BG_FileInfo *inFileInfo)
{
int numBuffersToQueue = kNumberBuffers;
UInt32 maxPacketSize;
UInt32 size = sizeof(maxPacketSize);
// we need to calculate how many packets we read at a time, and how big a buffer we need
// we base this on the size of the packets in the file and an approximate duration for each buffer
// first check to see what the max size of a packet is - if it is bigger
// than our allocation default size, that needs to become larger
OSStatus result = AudioFileGetProperty(inFileInfo->mAFID, kAudioFilePropertyPacketSizeUpperBound, &size, &maxPacketSize);
AssertNoError("Error getting packet upper bound size", end);
bool isFormatVBR = (inFileInfo->mFileFormat.mBytesPerPacket == 0 || inFileInfo- >mFileFormat.mFramesPerPacket == 0);
CalculateBytesForTime(inFileInfo->mFileFormat, maxPacketSize, 0.5/*seconds*/, &mBufferByteSize, &mNumPacketsToRead);
// if the file is smaller than the capacity of all the buffer queues, always load it at once
if ((mBufferByteSize * numBuffersToQueue) > inFileInfo->mFileDataSize)
inFileInfo->mLoadAtOnce = true;
if (inFileInfo->mLoadAtOnce)
{
UInt64 theFileNumPackets;
size = sizeof(UInt64);
result = AudioFileGetProperty(inFileInfo->mAFID, kAudioFilePropertyAudioDataPacketCount, &size, &theFileNumPackets);
AssertNoError("Error getting packet count for file", end);***>>>>this is where xcode says undefined<<<<***
mNumPacketsToRead = (UInt32)theFileNumPackets;
mBufferByteSize = inFileInfo->mFileDataSize;
numBuffersToQueue = 1;
}
//Here is the exact error
label 'end' used but not defined
I have that error twice
If you look at the SoundEngine.cpp source that the snippet comes from, you'll see it's defined on the very next line:
end:
return result;
It's a label that execution jumps to when there's an error.
Uhm, the only place I can find AssertNoError is here in Technical Note TN2113. And it has a completely different format. AssertNoError(theError, "couldn't unregister the ABL"); Where is AssertNoError defined?
User #Jeremy P mentions this document as well.
I was recently asked to complete a task for a c++ role, however as the application was decided not to be progressed any further I thought that I would post here for some feedback / advice / improvements / reminder of concepts I've forgotten.
The task was:
The following data is a time series of integer values
int timeseries[32] = {67497, 67376, 67173, 67235, 67057, 67031, 66951,
66974, 67042, 67025, 66897, 67077, 67082, 67033, 67019, 67149, 67044,
67012, 67220, 67239, 66893, 66984, 66866, 66693, 66770, 66722, 66620,
66579, 66596, 66713, 66852, 66715};
The series might be, for example, the closing price of a stock each day
over a 32 day period.
As stored above, the data will occupy 32 x sizeof(int) bytes = 128 bytes
assuming 4 byte ints.
Using delta encoding , write a function to compress, and a function to
uncompress data like the above.
Ok, so before this point I had never looked at compression so my solution is far from perfect. The manner in which I approached the problem is by compressing the array of integers into a array of bytes. When representing the integer as a byte I keep the calculate most
significant byte (msb) and keep everything up to this point, whilst throwing the rest away. This is then added to the byte array. For negative values I increment the msb by 1 so that we can
differentiate between positive and negative bytes when decoding by keeping the leading
1 bit values.
When decoding I parse this jagged byte array and simply reverse my
previous actions performed when compressing. As mentioned I have never looked at compression prior to this task so I did come up with my own method to compress the data. I was looking at C++/Cli recently, had not really used it previously so just decided to write it in this language, no particular reason. Below is the class, and a unit test at the very bottom. Any advice / improvements / enhancements will be much appreciated.
Thanks.
array<array<Byte>^>^ CDeltaEncoding::CompressArray(array<int>^ data)
{
int temp = 0;
int original;
int size = 0;
array<int>^ tempData = gcnew array<int>(data->Length);
data->CopyTo(tempData, 0);
array<array<Byte>^>^ byteArray = gcnew array<array<Byte>^>(tempData->Length);
for (int i = 0; i < tempData->Length; ++i)
{
original = tempData[i];
tempData[i] -= temp;
temp = original;
int msb = GetMostSignificantByte(tempData[i]);
byteArray[i] = gcnew array<Byte>(msb);
System::Buffer::BlockCopy(BitConverter::GetBytes(tempData[i]), 0, byteArray[i], 0, msb );
size += byteArray[i]->Length;
}
return byteArray;
}
array<int>^ CDeltaEncoding::DecompressArray(array<array<Byte>^>^ buffer)
{
System::Collections::Generic::List<int>^ decodedArray = gcnew System::Collections::Generic::List<int>();
int temp = 0;
for (int i = 0; i < buffer->Length; ++i)
{
int retrievedVal = GetValueAsInteger(buffer[i]);
decodedArray->Add(retrievedVal);
decodedArray[i] += temp;
temp = decodedArray[i];
}
return decodedArray->ToArray();
}
int CDeltaEncoding::GetMostSignificantByte(int value)
{
array<Byte>^ tempBuf = BitConverter::GetBytes(Math::Abs(value));
int msb = tempBuf->Length;
for (int i = tempBuf->Length -1; i >= 0; --i)
{
if (tempBuf[i] != 0)
{
msb = i + 1;
break;
}
}
if (!IsPositiveInteger(value))
{
//We need an extra byte to differentiate the negative integers
msb++;
}
return msb;
}
bool CDeltaEncoding::IsPositiveInteger(int value)
{
return value / Math::Abs(value) == 1;
}
int CDeltaEncoding::GetValueAsInteger(array<Byte>^ buffer)
{
array<Byte>^ tempBuf;
if(buffer->Length % 2 == 0)
{
//With even integers there is no need to allocate a new byte array
tempBuf = buffer;
}
else
{
tempBuf = gcnew array<Byte>(4);
System::Buffer::BlockCopy(buffer, 0, tempBuf, 0, buffer->Length );
unsigned int val = buffer[buffer->Length-1] &= 0xFF;
if ( val == 0xFF )
{
//We have negative integer compressed into 3 bytes
//Copy over the this last byte as well so we keep the negative pattern
System::Buffer::BlockCopy(buffer, buffer->Length-1, tempBuf, buffer->Length, 1 );
}
}
switch(tempBuf->Length)
{
case sizeof(short):
return BitConverter::ToInt16(tempBuf,0);
case sizeof(int):
default:
return BitConverter::ToInt32(tempBuf,0);
}
}
And then in a test class I had:
void CTestDeltaEncoding::TestCompression()
{
array<array<Byte>^>^ byteArray = CDeltaEncoding::CompressArray(m_testdata);
array<int>^ decompressedArray = CDeltaEncoding::DecompressArray(byteArray);
int totalBytes = 0;
for (int i = 0; i<byteArray->Length; i++)
{
totalBytes += byteArray[i]->Length;
}
Assert::IsTrue(m_testdata->Length * sizeof(m_testdata) > totalBytes, "Expected the total bytes to be less than the original array!!");
//Expected totalBytes = 53
}
This smells a lot like homework to me. The crucial phrase is: "Using delta encoding."
Delta encoding means you encode the delta (difference) between each number and the next:
67497, 67376, 67173, 67235, 67057, 67031, 66951, 66974, 67042, 67025, 66897, 67077, 67082, 67033, 67019, 67149, 67044, 67012, 67220, 67239, 66893, 66984, 66866, 66693, 66770, 66722, 66620, 66579, 66596, 66713, 66852, 66715
would turn into:
[Base: 67497]: -121, -203, +62
and so on. Assuming 8-bit bytes, the original numbers require 3 bytes apiece (and given the number of compilers with 3-byte integer types, you're normally going to end up with 4 bytes apiece). From the looks of things, the differences will fit quite easily in 2 bytes apiece, and if you can ignore one (or possibly two) of the least significant bits, you can fit them in one byte apiece.
Delta encoding is most often used for things like sound encoding where you can "fudge" the accuracy at times without major problems. For example, if you have a change from one sample to the next that's larger than you've left space to encode, you can encode a maximum change in the current difference, and add the difference to the next delta (and if you don't mind some back-tracking, you can distribute some to the previous delta as well). This will act as a low-pass filter, limiting the gradient between samples.
For example, in the series you gave, a simple delta encoding requires ten bits to represent all the differences. By dropping the LSB, however, nearly all the samples (all but one, in fact) can be encoded in 8 bits. That one has a difference (right shifted one bit) of -173, so if we represent it as -128, we have 45 left. We can distribute that error evenly between the preceding and following sample. In that case, the output won't be an exact match for the input, but if we're talking about something like sound, the difference probably won't be particularly obvious.
I did mention that it was an exercise that I had to complete and the solution that I received was deemed not good enough, so I wanted some constructive feedback seeing as actual companies never decide to tell you what you did wrong.
When the array is compressed I store the differences and not the original values except the first as this was my understanding. If you had looked at my code I have provided a full solution but my question was how bad was it?