Using fgmres_full_funct sample

Ivan_R_1 · ‎09-07-2017

Dear Intel MKL User,

I try to see into a matter of MKL for solving systems of second order with symmetrical and unsymmetrical matrixes. Therefore I tried to analyze the examples and got stuck with part of code fgmres_full_funct with preconditioner calling. I didn't understand the code below (especially for tmp(ipar(23)+0,1,..4) assignment.

I wonder if anyone could explain it:

! If RCI_REQUEST=3, then apply the preconditioner on the vector
! TMP(IPAR(22)) and put the result in vector TMP(IPAR(23))
!---------------------------------------------------------------------------
      IF (RCI_REQUEST.EQ.3) THEN
         IF (IPAR(4).EQ.3) THEN
             TMP(IPAR(23)+0)=-2.0D0
             TMP(IPAR(23)+1)= 0.08519601586107672D0
             TMP(IPAR(23)+2)=-1.1590871369607090D0
             TMP(IPAR(23)+3)=-0.65791939687456980D0
             TMP(IPAR(23)+4)= 0.75660051476696133D0
         ELSE
             IF(IPAR(4).EQ.4) THEN
                 TMP(IPAR(23)+0)= 0.0D0
                 TMP(IPAR(23)+1)= 0.0D0
                 TMP(IPAR(23)+2)= 0.0D0
                 TMP(IPAR(23)+3)= 1.0D0
                 TMP(IPAR(23)+4)=-1.0D0
             ELSE
             DO I=0,N-1
                 TMP(IPAR(23)+I)=I*TMP(IPAR(22)+I)
             ENDDO
             ENDIF
         ENDIF

GOTO 1
ENDIF

Thanks

Ivan

Gennady_F_Intel · ‎09-07-2017

RCI_request= 3	apply the preconditioner to `tmp[ipar[21] - 1:ipar[21] + n - 2]`, put the result in`tmp[ipar[22] - 1:ipar[22] + n - 2]`, and return the control to the dfgmres routine.
RCI_request= 4	check if the norm of the current orthogonal vector is zero, within the rounding or computational errors. Return the control to the dfgmres routine if it is not zero, otherwise complete the solution process by calling dfgmres_get routine.