dasum.c: GSL CBLAS real double-precision sum of absolute values

• Thin wrapper that instantiates the generic kernel source_asum_r.h at type double. Verified in LAProof.C.cblas.verif_dasum against the functional model LAProof.C.cblas.asum_model.

/* The following GSL headers are commented out for clightgen: they are
   unresolvable here (GSL's gsl/ symlink dir is not generated) and contribute
   nothing to cblas_dasum's body beyond the libc fabs, which we obtain directly
   from <math.h> (as the other LAProof C sources do, e.g. densemat.c). */
/* #include <gsl/gsl_math.h>  */
/* #include <gsl/gsl_cblas.h> */
#include <math.h>
#include "cblas.h"

double
cblas_dasum (const int N, const double *X, const int incX)
{
#define BASE double
#include "source_asum_r.h"
#undef BASE
}

Accumulation kernel (source_asum_r.h)

• A forward, left-to-right accumulation of fabs(X[ix]) into r, starting from +0.0. The incX <= 0 guard returns 0 for nonpositive stride; with unit stride (incX = 1) it is dead and ix advances one element per iteration.

{
  BASE r = 0.0;
  INDEX i;
  INDEX ix = 0;

  if (incX <= 0) {
    return 0;
  }

  for (i = 0; i < N; i++) {
    r += fabs(X[ix]);
    ix += incX;
  }
  return r;
}