| Line | |
|---|
| 1 | SUBROUTINE DAXPY(N,DA,DX,INCX,DY,INCY) |
|---|
| 2 | * .. Scalar Arguments .. |
|---|
| 3 | DOUBLE PRECISION DA |
|---|
| 4 | INTEGER INCX,INCY,N |
|---|
| 5 | * .. |
|---|
| 6 | * .. Array Arguments .. |
|---|
| 7 | DOUBLE PRECISION DX(*),DY(*) |
|---|
| 8 | * .. |
|---|
| 9 | * |
|---|
| 10 | * Purpose |
|---|
| 11 | * ======= |
|---|
| 12 | * |
|---|
| 13 | * constant times a vector plus a vector. |
|---|
| 14 | * uses unrolled loops for increments equal to one. |
|---|
| 15 | * jack dongarra, linpack, 3/11/78. |
|---|
| 16 | * modified 12/3/93, array(1) declarations changed to array(*) |
|---|
| 17 | * |
|---|
| 18 | * |
|---|
| 19 | * .. Local Scalars .. |
|---|
| 20 | INTEGER I,IX,IY,M,MP1 |
|---|
| 21 | * .. |
|---|
| 22 | * .. Intrinsic Functions .. |
|---|
| 23 | INTRINSIC MOD |
|---|
| 24 | * .. |
|---|
| 25 | IF (N.LE.0) RETURN |
|---|
| 26 | IF (DA.EQ.0.0d0) RETURN |
|---|
| 27 | IF (INCX.EQ.1 .AND. INCY.EQ.1) GO TO 20 |
|---|
| 28 | * |
|---|
| 29 | * code for unequal increments or equal increments |
|---|
| 30 | * not equal to 1 |
|---|
| 31 | * |
|---|
| 32 | IX = 1 |
|---|
| 33 | IY = 1 |
|---|
| 34 | IF (INCX.LT.0) IX = (-N+1)*INCX + 1 |
|---|
| 35 | IF (INCY.LT.0) IY = (-N+1)*INCY + 1 |
|---|
| 36 | DO 10 I = 1,N |
|---|
| 37 | DY(IY) = DY(IY) + DA*DX(IX) |
|---|
| 38 | IX = IX + INCX |
|---|
| 39 | IY = IY + INCY |
|---|
| 40 | 10 CONTINUE |
|---|
| 41 | RETURN |
|---|
| 42 | * |
|---|
| 43 | * code for both increments equal to 1 |
|---|
| 44 | * |
|---|
| 45 | * |
|---|
| 46 | * clean-up loop |
|---|
| 47 | * |
|---|
| 48 | 20 M = MOD(N,4) |
|---|
| 49 | IF (M.EQ.0) GO TO 40 |
|---|
| 50 | DO 30 I = 1,M |
|---|
| 51 | DY(I) = DY(I) + DA*DX(I) |
|---|
| 52 | 30 CONTINUE |
|---|
| 53 | IF (N.LT.4) RETURN |
|---|
| 54 | 40 MP1 = M + 1 |
|---|
| 55 | DO 50 I = MP1,N,4 |
|---|
| 56 | DY(I) = DY(I) + DA*DX(I) |
|---|
| 57 | DY(I+1) = DY(I+1) + DA*DX(I+1) |
|---|
| 58 | DY(I+2) = DY(I+2) + DA*DX(I+2) |
|---|
| 59 | DY(I+3) = DY(I+3) + DA*DX(I+3) |
|---|
| 60 | 50 CONTINUE |
|---|
| 61 | RETURN |
|---|
| 62 | END |
|---|
Note: See
TracBrowser
for help on using the repository browser.
