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Annotation of rpl/lapack/blas/dscal.f, revision 1.2

1.1       bertrand    1:       SUBROUTINE DSCAL(N,DA,DX,INCX)
                      2: *     .. Scalar Arguments ..
                      3:       DOUBLE PRECISION DA
                      4:       INTEGER INCX,N
                      5: *     ..
                      6: *     .. Array Arguments ..
                      7:       DOUBLE PRECISION DX(*)
                      8: *     ..
                      9: *
                     10: *  Purpose
                     11: *  =======
                     12: *
                     13: *     DSCAL scales a vector by a constant.
                     14: *     uses unrolled loops for increment equal to one.
                     15: *
                     16: *  Further Details
                     17: *  ===============
                     18: *
                     19: *     jack dongarra, linpack, 3/11/78.
                     20: *     modified 3/93 to return if incx .le. 0.
                     21: *     modified 12/3/93, array(1) declarations changed to array(*)
                     22: *
                     23: *  =====================================================================
                     24: *
                     25: *     .. Local Scalars ..
                     26:       INTEGER I,M,MP1,NINCX
                     27: *     ..
                     28: *     .. Intrinsic Functions ..
                     29:       INTRINSIC MOD
                     30: *     ..
                     31:       IF (N.LE.0 .OR. INCX.LE.0) RETURN
                     32:       IF (INCX.EQ.1) GO TO 20
                     33: *
                     34: *        code for increment not equal to 1
                     35: *
                     36:       NINCX = N*INCX
                     37:       DO 10 I = 1,NINCX,INCX
                     38:           DX(I) = DA*DX(I)
                     39:    10 CONTINUE
                     40:       RETURN
                     41: *
                     42: *        code for increment equal to 1
                     43: *
                     44: *
                     45: *        clean-up loop
                     46: *
                     47:    20 M = MOD(N,5)
                     48:       IF (M.EQ.0) GO TO 40
                     49:       DO 30 I = 1,M
                     50:           DX(I) = DA*DX(I)
                     51:    30 CONTINUE
                     52:       IF (N.LT.5) RETURN
                     53:    40 MP1 = M + 1
                     54:       DO 50 I = MP1,N,5
                     55:           DX(I) = DA*DX(I)
                     56:           DX(I+1) = DA*DX(I+1)
                     57:           DX(I+2) = DA*DX(I+2)
                     58:           DX(I+3) = DA*DX(I+3)
                     59:           DX(I+4) = DA*DX(I+4)
                     60:    50 CONTINUE
                     61:       RETURN
                     62:       END