Zhang Xianyi
commit
17d655fa64
|
|
@ -0,0 +1,199 @@
|
|||
# Notes on OpenBLAS usage
|
||||
## Usage
|
||||
|
||||
#### Program is Terminated. Because you tried to allocate too many memory regions
|
||||
|
||||
In OpenBLAS, we mange a pool of memory buffers and allocate the number of
|
||||
buffers as the following.
|
||||
```
|
||||
#define NUM_BUFFERS (MAX_CPU_NUMBER * 2)
|
||||
```
|
||||
This error indicates that the program exceeded the number of buffers.
|
||||
|
||||
Please build OpenBLAS with larger `NUM_THREADS`. For example, `make
|
||||
NUM_THREADS=32` or `make NUM_THREADS=64`. In `Makefile.system`, we will set
|
||||
`MAX_CPU_NUMBER=NUM_THREADS`.
|
||||
|
||||
#### How can I use OpenBLAS in multi-threaded applications?
|
||||
|
||||
If your application is already multi-threaded, it will conflict with OpenBLAS
|
||||
multi-threading. Thus, you must set OpenBLAS to use single thread in any of the
|
||||
following ways:
|
||||
|
||||
* `export OPENBLAS_NUM_THREADS=1` in the environment variables.
|
||||
* Call `openblas_set_num_threads(1)` in the application on runtime.
|
||||
* Build OpenBLAS single thread version, e.g. `make USE_THREAD=0`
|
||||
|
||||
If the application is parallelized by OpenMP, please use OpenBLAS built with
|
||||
`USE_OPENMP=1`
|
||||
|
||||
#### How to choose TARGET manually at runtime when compiled with DYNAMIC_ARCH
|
||||
|
||||
The environment variable which control the kernel selection is
|
||||
`OPENBLAS_CORETYPE` (see `driver/others/dynamic.c`) e.g. `export
|
||||
OPENBLAS_CORETYPE=Haswell` and the function `char* openblas_get_corename()`
|
||||
returns the used target.
|
||||
|
||||
#### How could I disable OpenBLAS threading affinity on runtime?
|
||||
|
||||
You can define the `OPENBLAS_MAIN_FREE` or `GOTOBLAS_MAIN_FREE` environment
|
||||
variable to disable threading affinity on runtime. For example, before the
|
||||
running,
|
||||
```
|
||||
export OPENBLAS_MAIN_FREE=1
|
||||
```
|
||||
|
||||
Alternatively, you can disable affinity feature with enabling `NO_AFFINITY=1`
|
||||
in `Makefile.rule`.
|
||||
|
||||
## Linking with the library
|
||||
|
||||
* Link with shared library
|
||||
|
||||
`gcc -o test test.c -I /your_path/OpenBLAS/include/ -L/your_path/OpenBLAS/lib -lopenblas`
|
||||
|
||||
If the library is multithreaded, please add `-lpthread`. If the library
|
||||
contains LAPACK functions, please add `-lgfortran` or other Fortran libs.
|
||||
|
||||
* Link with static library
|
||||
|
||||
`gcc -o test test.c /your/path/libopenblas.a`
|
||||
|
||||
You can download `test.c` from https://gist.github.com/xianyi/5780018
|
||||
|
||||
On Linux, if OpenBLAS was compiled with threading support (`USE_THREAD=1` by
|
||||
default), custom programs statically linked against `libopenblas.a` should also
|
||||
link with the pthread library e.g.:
|
||||
|
||||
```
|
||||
gcc -static -I/opt/OpenBLAS/include -L/opt/OpenBLAS/lib -o my_program my_program.c -lopenblas -lpthread
|
||||
```
|
||||
|
||||
Failing to add the `-lpthread` flag will cause errors such as:
|
||||
|
||||
```
|
||||
/opt/OpenBLAS/libopenblas.a(memory.o): In function `_touch_memory':
|
||||
memory.c:(.text+0x15): undefined reference to `pthread_mutex_lock'
|
||||
memory.c:(.text+0x41): undefined reference to `pthread_mutex_unlock'
|
||||
...
|
||||
```
|
||||
|
||||
## Code examples
|
||||
|
||||
#### Call CBLAS interface
|
||||
This example shows calling cblas_dgemm in C. https://gist.github.com/xianyi/6930656
|
||||
```
|
||||
#include <cblas.h>
|
||||
#include <stdio.h>
|
||||
|
||||
void main()
|
||||
{
|
||||
int i=0;
|
||||
double A[6] = {1.0,2.0,1.0,-3.0,4.0,-1.0};
|
||||
double B[6] = {1.0,2.0,1.0,-3.0,4.0,-1.0};
|
||||
double C[9] = {.5,.5,.5,.5,.5,.5,.5,.5,.5};
|
||||
cblas_dgemm(CblasColMajor, CblasNoTrans, CblasTrans,3,3,2,1,A, 3, B, 3,2,C,3);
|
||||
|
||||
for(i=0; i<9; i++)
|
||||
printf("%lf ", C[i]);
|
||||
printf("\n");
|
||||
}
|
||||
```
|
||||
`gcc -o test_cblas_open test_cblas_dgemm.c -I /your_path/OpenBLAS/include/ -L/your_path/OpenBLAS/lib -lopenblas -lpthread -lgfortran`
|
||||
|
||||
#### Call BLAS Fortran interface
|
||||
|
||||
This example shows calling dgemm Fortran interface in C. https://gist.github.com/xianyi/5780018
|
||||
|
||||
```
|
||||
#include "stdio.h"
|
||||
#include "stdlib.h"
|
||||
#include "sys/time.h"
|
||||
#include "time.h"
|
||||
|
||||
extern void dgemm_(char*, char*, int*, int*,int*, double*, double*, int*, double*, int*, double*, double*, int*);
|
||||
|
||||
int main(int argc, char* argv[])
|
||||
{
|
||||
int i;
|
||||
printf("test!\n");
|
||||
if(argc<4){
|
||||
printf("Input Error\n");
|
||||
return 1;
|
||||
}
|
||||
|
||||
int m = atoi(argv[1]);
|
||||
int n = atoi(argv[2]);
|
||||
int k = atoi(argv[3]);
|
||||
int sizeofa = m * k;
|
||||
int sizeofb = k * n;
|
||||
int sizeofc = m * n;
|
||||
char ta = 'N';
|
||||
char tb = 'N';
|
||||
double alpha = 1.2;
|
||||
double beta = 0.001;
|
||||
|
||||
struct timeval start,finish;
|
||||
double duration;
|
||||
|
||||
double* A = (double*)malloc(sizeof(double) * sizeofa);
|
||||
double* B = (double*)malloc(sizeof(double) * sizeofb);
|
||||
double* C = (double*)malloc(sizeof(double) * sizeofc);
|
||||
|
||||
srand((unsigned)time(NULL));
|
||||
|
||||
for (i=0; i<sizeofa; i++)
|
||||
A[i] = i%3+1;//(rand()%100)/10.0;
|
||||
|
||||
for (i=0; i<sizeofb; i++)
|
||||
B[i] = i%3+1;//(rand()%100)/10.0;
|
||||
|
||||
for (i=0; i<sizeofc; i++)
|
||||
C[i] = i%3+1;//(rand()%100)/10.0;
|
||||
//#if 0
|
||||
printf("m=%d,n=%d,k=%d,alpha=%lf,beta=%lf,sizeofc=%d\n",m,n,k,alpha,beta,sizeofc);
|
||||
gettimeofday(&start, NULL);
|
||||
dgemm_(&ta, &tb, &m, &n, &k, &alpha, A, &m, B, &k, &beta, C, &m);
|
||||
gettimeofday(&finish, NULL);
|
||||
|
||||
duration = ((double)(finish.tv_sec-start.tv_sec)*1000000 + (double)(finish.tv_usec-start.tv_usec)) / 1000000;
|
||||
double gflops = 2.0 * m *n*k;
|
||||
gflops = gflops/duration*1.0e-6;
|
||||
|
||||
FILE *fp;
|
||||
fp = fopen("timeDGEMM.txt", "a");
|
||||
fprintf(fp, "%dx%dx%d\t%lf s\t%lf MFLOPS\n", m, n, k, duration, gflops);
|
||||
fclose(fp);
|
||||
|
||||
free(A);
|
||||
free(B);
|
||||
free(C);
|
||||
return 0;
|
||||
}
|
||||
```
|
||||
|
||||
` gcc -o time_dgemm time_dgemm.c /your/path/libopenblas.a`
|
||||
|
||||
` ./time_dgemm <m> <n> <k> `
|
||||
|
||||
## Troubleshooting
|
||||
* Please read [Faq](https://github.com/xianyi/OpenBLAS/wiki/Faq) at first.
|
||||
* Please use gcc version 4.6 and above to compile Sandy Bridge AVX kernels on Linux/MingW/BSD.
|
||||
* Please use Clang version 3.1 and above to compile the library on Sandy Bridge microarchitecture. The Clang 3.0 will generate the wrong AVX binary code.
|
||||
* The number of CPUs/Cores should less than or equal to 256. On Linux x86_64(amd64), there is experimental support for up to 1024 CPUs/Cores and 128 numa nodes if you build the library with BIGNUMA=1.
|
||||
* OpenBLAS does not set processor affinity by default. On Linux, you can enable processor affinity by commenting the line NO_AFFINITY=1 in Makefile.rule. But this may cause [the conflict with R parallel](https://stat.ethz.ch/pipermail/r-sig-hpc/2012-April/001348.html).
|
||||
* On Loongson 3A. make test would be failed because of pthread_create error. The error code is EAGAIN. However, it will be OK when you run the same testcase on shell.
|
||||
|
||||
## BLAS reference manual
|
||||
If you want to understand every BLAS function and definition, please read
|
||||
[Intel MKL reference manual](https://software.intel.com/sites/products/documentation/doclib/iss/2013/mkl/mklman/GUID-F7ED9FB8-6663-4F44-A62B-61B63C4F0491.htm)
|
||||
or [netlib.org](http://netlib.org/blas/)
|
||||
|
||||
Here are [OpenBLAS extension functions](https://github.com/xianyi/OpenBLAS/wiki/OpenBLAS-Extensions)
|
||||
|
||||
## How to reference OpenBLAS.
|
||||
|
||||
You can reference our [papers](https://github.com/xianyi/OpenBLAS/wiki/publications).
|
||||
|
||||
Alternatively, you can cite the OpenBLAS homepage http://www.openblas.net directly.
|
||||
|
||||
Loading…
Reference in New Issue