ddot.c: GSL CBLAS real double-precision dot product

• Thin wrapper that instantiates the generic kernel source_dot_r.h at type double. Verified in LAProof.C.cblas.verif_ddot against the functional model LAProof.C.cblas.ddot_model.

/* The following GSL headers are commented out for clightgen: they are
   unused by cblas_ddot's body (only OFFSET/INDEX from "cblas.h" are needed)
   and are unresolvable here because GSL's gsl/ symlink dir is not generated. */
/* #include <gsl/gsl_math.h>  */
/* #include <gsl/gsl_cblas.h> */
#include "cblas.h"

double
cblas_ddot (const int N, const double *X, const int incX, const double *Y,
            const int incY)
{
#define INIT_VAL  0.0
#define ACC_TYPE  double
#define BASE double
#include "source_dot_r.h"
#undef ACC_TYPE
#undef BASE
#undef INIT_VAL
}

Accumulation kernel (source_dot_r.h)

• A forward, left-to-right accumulation with separate multiply-then-add (not fused). With unit stride (incX = incY = 1) the OFFSET conditionals are 0 and the indices ix, iy advance one element per iteration.

{
  ACC_TYPE r = INIT_VAL;
  INDEX i;
  INDEX ix = OFFSET(N, incX);
  INDEX iy = OFFSET(N, incY);

  for (i = 0; i < N; i++) {
    r += X[ix] * Y[iy];
    ix += incX;
    iy += incY;
  }

  return r;
}