crash in zscal

[juliantaylor]

yet another crash, x86 32 bit in kernel/x86/zscal_sse2.S:131, fedora 11 gcc 4.4.1, git head
and x86_64 in kernel/x86_64/zscal_sse2.S:115, SLC 5.5 gcc 4.4.0, git head

also reproduced on ubuntu 13.10 with gcc 4.7.2 and the openblas package (0.2.5)

the code works perfectly fine with gsl or atlas on all tested platforms
decreasing k to to ~ 600 works,

#include <stdio.h>
#include <stdlib.h>
#include <cblas.h>

int main(int argc, const char *argv[])
{
    blasint m = 100;
    blasint k = 6000;
    double * a = calloc(m*k,sizeof(double complex));
    double * b = calloc(m*k,sizeof(double complex));
    double * c = calloc(m*k,sizeof(double complex));
    printf("%gMB\n", m*k*sizeof(double complex)/1024./1024.);
    double complex alpha = 1;
    double complex beta = 1;
    cblas_zhbmv(CblasRowMajor, CblasLower, m*k, 0, (double*)&alpha, a, 1, b, 1, (double*)&beta, c, 1);

    return 0;
}

[xianyi]

Thank you for the feedback.

We will debug next week

Xianyi

[xianyi]

Hi @juliantaylor ,

I already found the reason for the bug. This bug only happens with multithreading. Thread 0 created a buffer about 32MB. Every thread uses a part of this buffer to storing m complex numbers.

In your case, m is 6000*100 about 9.25MB. When OpenBLAS starts 4 threads, it will need 37MB which overflows the buffer.

Xianyi

[xianyi]

Hi @juliantaylor ,

I think I already fixed this bug on develop branch. Could you test it?

Xianyi

[juliantaylor]

seems to work now, thanks