dscal.c: GSL CBLAS real double-precision scaling (in place)

• Thin wrapper that instantiates the generic kernel source_scal_r.h at type double. Verified in LAProof.C.cblas.verif_dscal against the functional model LAProof.C.cblas.scal_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_dscal's body (only INDEX from "cblas.h" is needed; the loop
   uses no libc math). */
/* #include <gsl/gsl_math.h>  */
/* #include <gsl/gsl_cblas.h> */
#include "cblas.h"

void
cblas_dscal (const int N, const double alpha, double *X, const int incX)
{
#define BASE double
#include "source_scal_r.h"
#undef BASE
}

Scaling kernel (source_scal_r.h)

• An in-place elementwise update X[ix] *= alpha with no accumulation. The incX <= 0 guard returns early for nonpositive stride; with unit stride (incX = 1) it is dead and ix advances one element per iteration.

{
  INDEX i;
  INDEX ix = 0;

  if (incX <= 0) {
    return;
  }

  for (i = 0; i < N; i++) {
    X[ix] *= alpha;
    ix += incX;
  }
}