Unable to use LAPACK - potrs functions

Hi,

    Sorry to hear you are having an issue with APL. We are interested to understand more about this issue, please can you provide me with further information?

Can you tell me which compiler you are using to compiler your code and which version of APL you are using? Also, are you using the static library or the DLL and are you using either the MD or the MT variant?

In the case where you report using  'extern "C" void zpotrs_' declarations failing, can you tell me if this is a) failing to compile; b) failing to link; c) giving an error when running ?

And in the second case where you report using "static inline void zpotrs_" it suggests you are successful, is that correct ? Or are the errors regarding "parameter number  1 had an illegal value" related to this case ?

Also, can you show the declaration and value of uplo ?

Thanks

Hello,

Thanks for the fast reply. 

We're using MSVC as the compiler. We worked with the last 3 releases of APL and the problem still remains with 24.10. We also tried using both static libraries and DLLs.

The compilation and the runtime are okay. It looks like it is failing to link, when the functions are called in the above method the result is always zero. But we can see the correct results when we use the second method. 

The "parameter number had an illegal value" errors are printed during the runtime, it looks like they do not affect our tests & their results. We did not fully investigate them. But with the second method, they also disappeared. 

Hope this helps for now, I'll share the answer to the last question in a bit.

Hi,

   I have found an example using zpotrs from NAG here

support.nag.com/.../f07fsf.html

which is in Fortran. I have tested this with our library and it seems to work correctly. I have converted this to c++ (and modified it slightly) and have compiled this directly with our library using the Microsoft cl.exe compiler with no issues. My code is below

#include <armpl.h>
#include <vector>
#include <iostream>
#include <iomanip>

int main () {

  const char uplo = 'L';
  const armpl_int_t n = 4;
  const armpl_int_t nrhs = 2;
  const armpl_int_t lda = n;
  std::vector<armpl_doublecomplex_t> a(lda*n);
  const armpl_int_t ldb = n;
  std::vector<armpl_doublecomplex_t> b(ldb*nrhs);
  armpl_int_t info = -1;

  // Initialize matrix A to zero
  for (int i = 0; i < n*lda; ++i) {
    a[i] = _Cbuild((double)(0.0), (double)(0.0));
  }

  // Set initial values
  a[0] = _Cbuild((double)(3.23), (double)(0.0));
  a[1] = _Cbuild((double)(1.51), (double)(1.92)); a[5] = _Cbuild((double)(3.58), (double)(0.0));
  a[2] = _Cbuild((double)(1.90), (double)(-0.84)); a[6] = _Cbuild((double)(-0.23), (double)(-1.11)); a[10] = _Cbuild((double)( 4.09), (double)( 0.00));
  a[3] = _Cbuild((double)(0.42), (double)(-2.50)); a[7] = _Cbuild((double)(-1.18), (double)(-1.37));
  a[11] = _Cbuild((double)( 2.33), (double)( 0.14)); a[15] = _Cbuild((double)( 4.29), (double)( 0.00));

  b[0] = _Cbuild((double)( 3.93), (double)( -6.14));  b[4] = _Cbuild((double)( 1.48), (double)(  6.58));
  b[1] = _Cbuild((double)( 6.17), (double)(  9.42));  b[5] = _Cbuild((double)( 4.65), (double)( -4.75));
  b[2] = _Cbuild((double)(-7.17), (double)(-21.83));  b[6] = _Cbuild((double)(-4.91), (double)(  2.29));
  b[3] = _Cbuild((double)( 1.99), (double)(-14.38));  b[7] = _Cbuild((double)( 7.64), (double)(-10.79));

  zpotrf_(&uplo,&n,a.data(),&lda,&info);

  if (info == 0) {
    zpotrs_(&uplo,&n,&nrhs,a.data(),&lda,b.data(),&ldb,&info);

    if (info == 0) {
      std::cout << std::fixed << std::setw(8) << std::setprecision(2) << "\n";
      std::cout << "Solution:\n";
      for (int i = 0 ; i < n; i++) {
        std::cout << i ;
        std::cout << " (" << creal(b[i]) << ", " <<  cimag(b[i]) << "), (" <<  creal(b[i+n]) << "," <<  cimag(b[i+n]) << ")\n";
      }
      std::cout << "\n";
      std::cout << "Expected:\n";
      std::cout << "0 (1.00, -1.00), (-1.00,2.00)\n";
      std::cout << "1 (-0.00, 3.00), (3.00,-4.00)\n";
      std::cout << "2 (-4.00, -5.00), (-2.00,3.00)\n";
      std::cout << "3 (2.00, 1.00), (4.00,-5.00)\n";
    }
    else {
      std::cout << "Error: zpotrs returned an error.\n";
    }
  }
  else {
    std::cout << "Error: zpotrf returned an error.\n";
  }

return 1;
}

I have compiled this code, called zpotrs_example.cpp,  in a windows command shell using the following commands

cl.exe -c /MT /nologo /EHsc /I"%ARMPL_DIR%\include"  zpotrs_example.cpp /Fozpotrs_example.obj
cl.exe /MT /Fezpotrs.exe zpotrs_example.obj libarmpl_lp64.dll.lib /link /libpath:"%ARMPL_DIR%"\lib

and then run it using

zpotrs.exe

Solution:
0 (1.00, -1.00), (-1.00,2.00)
1 (-0.00, 3.00), (3.00,-4.00)
2 (-4.00, -5.00), (-2.00,3.00)
3 (2.00, 1.00), (4.00,-5.00)

Expected:
0 (1.00, -1.00), (-1.00,2.00)
1 (-0.00, 3.00), (3.00,-4.00)
2 (-4.00, -5.00), (-2.00,3.00)
3 (2.00, 1.00), (4.00,-5.00)

If this fails for you or if it doesn't help you resolve the issue you are having please reach out to us at 

support-hpc-sw@arm.com