PROGRAM MAIN6
REAL A(4,6)
REAL X(6)
REAL Y(5)
DATA X/6*1.0/
DATA Y/5*0.0/
CALL READIN(A,4,6)
C CALL OPP(W,X1,X2)
C SUBROUTINE SGBMV(TRANS,M,N,KL,KU,ALPHA,A,LDA,X,INCX,BETA,Y,INCY)
CALL SGBMV('N',5,6,1,2,1.0,A,4,X,1,1.0,Y,1)
DO 100, I=1,5
PRINT*,Y(I)
100 CONTINUE
C PRINT*,'X1=',X1,' X2=',X2
END
SUBROUTINE READIN(A,LDA,N)
REAL A(LDA,N)
WRITE(*,*) 'Enter ',LDA,'*',N,' matrix:'
DO 10 I=1,LDA
READ(*,*)(A(I,J),J=1,N)
10 CONTINUE
END
SUBROUTINE OPP(A,S1,S2)
REAL A(5,5)
S1=0
DO 20 I=1,5
S1=S1+A(I,I)
20 CONTINUE
S2=0
DO 30 I=1,5
J=5-I+1
S2=S2+A(I,J)
30 CONTINUE
END
C SUBRU
SUBROUTINE SGBMV(TRANS,M,N,KL,KU,ALPHA,A,LDA,X,INCX,BETA,Y,INCY)
*
* -- Reference BLAS level2 routine --
* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
* .. Scalar Arguments ..
REAL ALPHA,BETA
INTEGER INCX,INCY,KL,KU,LDA,M,N
CHARACTER TRANS
* ..
* .. Array Arguments ..
REAL A(LDA,*),X(*),Y(*)
* ..
*
* =====================================================================
*
* .. Parameters ..
REAL ONE,ZERO
PARAMETER (ONE=1.0E+0,ZERO=0.0E+0)
* ..
* .. Local Scalars ..
REAL TEMP
INTEGER I,INFO,IX,IY,J,JX,JY,K,KUP1,KX,KY,LENX,LENY
* ..
* .. External Functions ..
LOGICAL LSAME
EXTERNAL LSAME
* ..
* .. External Subroutines ..
EXTERNAL XERBLA
* ..
* .. Intrinsic Functions ..
INTRINSIC MAX,MIN
* ..
*
* Test the input parameters.
*
INFO = 0
IF (.NOT.LSAME(TRANS,'N') .AND. .NOT.LSAME(TRANS,'T') .AND.
+ .NOT.LSAME(TRANS,'C')) THEN
INFO = 1
ELSE IF (M.LT.0) THEN
INFO = 2
ELSE IF (N.LT.0) THEN
INFO = 3
ELSE IF (KL.LT.0) THEN
INFO = 4
ELSE IF (KU.LT.0) THEN
INFO = 5
ELSE IF (LDA.LT. (KL+KU+1)) THEN
INFO = 8
ELSE IF (INCX.EQ.0) THEN
INFO = 10
ELSE IF (INCY.EQ.0) THEN
INFO = 13
END IF
IF (INFO.NE.0) THEN
CALL XERBLA('SGBMV ',INFO)
RETURN
END IF
*
* Quick return if possible.
*
IF ((M.EQ.0) .OR. (N.EQ.0) .OR.
+ ((ALPHA.EQ.ZERO).AND. (BETA.EQ.ONE))) RETURN
*
* Set LENX and LENY, the lengths of the vectors x and y, and set
* up the start points in X and Y.
*
IF (LSAME(TRANS,'N')) THEN
LENX = N
LENY = M
ELSE
LENX = M
LENY = N
END IF
IF (INCX.GT.0) THEN
KX = 1
ELSE
KX = 1 - (LENX-1)*INCX
END IF
IF (INCY.GT.0) THEN
KY = 1
ELSE
KY = 1 - (LENY-1)*INCY
END IF
*
* Start the operations. In this version the elements of A are
* accessed sequentially with one pass through the band part of A.
*
* First form y := beta*y.
*
IF (BETA.NE.ONE) THEN
IF (INCY.EQ.1) THEN
IF (BETA.EQ.ZERO) THEN
DO 10 I = 1,LENY
Y(I) = ZERO
10 CONTINUE
ELSE
DO 20 I = 1,LENY
Y(I) = BETA*Y(I)
20 CONTINUE
END IF
ELSE
IY = KY
IF (BETA.EQ.ZERO) THEN
DO 30 I = 1,LENY
Y(IY) = ZERO
IY = IY + INCY
30 CONTINUE
ELSE
DO 40 I = 1,LENY
Y(IY) = BETA*Y(IY)
IY = IY + INCY
40 CONTINUE
END IF
END IF
END IF
IF (ALPHA.EQ.ZERO) RETURN
KUP1 = KU + 1
IF (LSAME(TRANS,'N')) THEN
*
* Form y := alpha*A*x + y.
*
JX = KX
IF (INCY.EQ.1) THEN
DO 60 J = 1,N
TEMP = ALPHA*X(JX)
K = KUP1 - J
DO 50 I = MAX(1,J-KU),MIN(M,J+KL)
Y(I) = Y(I) + TEMP*A(K+I,J)
50 CONTINUE
JX = JX + INCX
60 CONTINUE
ELSE
DO 80 J = 1,N
TEMP = ALPHA*X(JX)
IY = KY
K = KUP1 - J
DO 70 I = MAX(1,J-KU),MIN(M,J+KL)
Y(IY) = Y(IY) + TEMP*A(K+I,J)
IY = IY + INCY
70 CONTINUE
JX = JX + INCX
IF (J.GT.KU) KY = KY + INCY
80 CONTINUE
END IF
ELSE
*
* Form y := alpha*A**T*x + y.
*
JY = KY
IF (INCX.EQ.1) THEN
DO 100 J = 1,N
TEMP = ZERO
K = KUP1 - J
DO 90 I = MAX(1,J-KU),MIN(M,J+KL)
TEMP = TEMP + A(K+I,J)*X(I)
90 CONTINUE
Y(JY) = Y(JY) + ALPHA*TEMP
JY = JY + INCY
100 CONTINUE
ELSE
DO 120 J = 1,N
TEMP = ZERO
IX = KX
K = KUP1 - J
DO 110 I = MAX(1,J-KU),MIN(M,J+KL)
TEMP = TEMP + A(K+I,J)*X(IX)
IX = IX + INCX
110 CONTINUE
Y(JY) = Y(JY) + ALPHA*TEMP
JY = JY + INCY
IF (J.GT.KU) KX = KX + INCX
120 CONTINUE
END IF
END IF
*
RETURN
*
* End of SGBMV
*
END
LOGICAL FUNCTION LSAME(CA,CB)
*
* -- Reference BLAS level1 routine --
* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
* .. Scalar Arguments ..
CHARACTER CA,CB
* ..
*
* =====================================================================
*
* .. Intrinsic Functions ..
INTRINSIC ICHAR
* ..
* .. Local Scalars ..
INTEGER INTA,INTB,ZCODE
* ..
*
* Test if the characters are equal
*
LSAME = CA .EQ. CB
IF (LSAME) RETURN
*
* Now test for equivalence if both characters are alphabetic.
*
ZCODE = ICHAR('Z')
*
* Use 'Z' rather than 'A' so that ASCII can be detected on Prime
* machines, on which ICHAR returns a value with bit 8 set.
* ICHAR('A') on Prime machines returns 193 which is the same as
* ICHAR('A') on an EBCDIC machine.
*
INTA = ICHAR(CA)
INTB = ICHAR(CB)
*
IF (ZCODE.EQ.90 .OR. ZCODE.EQ.122) THEN
*
* ASCII is assumed - ZCODE is the ASCII code of either lower or
* upper case 'Z'.
*
IF (INTA.GE.97 .AND. INTA.LE.122) INTA = INTA - 32
IF (INTB.GE.97 .AND. INTB.LE.122) INTB = INTB - 32
*
ELSE IF (ZCODE.EQ.233 .OR. ZCODE.EQ.169) THEN
*
* EBCDIC is assumed - ZCODE is the EBCDIC code of either lower or
* upper case 'Z'.
*
IF (INTA.GE.129 .AND. INTA.LE.137 .OR.
+ INTA.GE.145 .AND. INTA.LE.153 .OR.
+ INTA.GE.162 .AND. INTA.LE.169) INTA = INTA + 64
IF (INTB.GE.129 .AND. INTB.LE.137 .OR.
+ INTB.GE.145 .AND. INTB.LE.153 .OR.
+ INTB.GE.162 .AND. INTB.LE.169) INTB = INTB + 64
*
ELSE IF (ZCODE.EQ.218 .OR. ZCODE.EQ.250) THEN
*
* ASCII is assumed, on Prime machines - ZCODE is the ASCII code
* plus 128 of either lower or upper case 'Z'.
*
IF (INTA.GE.225 .AND. INTA.LE.250) INTA = INTA - 32
IF (INTB.GE.225 .AND. INTB.LE.250) INTB = INTB - 32
END IF
LSAME = INTA .EQ. INTB
*
* RETURN
*
* End of LSAME
*
END
SUBROUTINE XERBLA( SRNAME, INFO )
*
* This is a special version of XERBLA to be used only as part of
* the test program for testing error exits from the Level 2 BLAS
* routines.
*
* XERBLA is an error handler for the Level 2 BLAS routines.
*
* It is called by the Level 2 BLAS routines if an input parameter is
* invalid.
*
* Auxiliary routine for test program for Level 2 Blas.
*
* -- Written on 10-August-1987.
* Richard Hanson, Sandia National Labs.
* Jeremy Du Croz, NAG Central Office.
*
* .. Scalar Arguments ..
INTEGER INFO
CHARACTER*6 SRNAME
* .. Scalars in Common ..
INTEGER INFOT, NOUT
LOGICAL LERR, OK
CHARACTER*6 SRNAMT
* .. Common blocks ..
COMMON /INFOC/INFOT, NOUT, OK, LERR
COMMON /SRNAMC/SRNAMT
* .. Executable Statements ..
LERR = .TRUE.
IF( INFO.NE.INFOT )THEN
IF( INFOT.NE.0 )THEN
WRITE( NOUT, FMT = 9999 )INFO, INFOT
ELSE
WRITE( NOUT, FMT = 9997 )INFO
END IF
OK = .FALSE.
END IF
IF( SRNAME.NE.SRNAMT )THEN
WRITE( NOUT, FMT = 9998 )SRNAME, SRNAMT
OK = .FALSE.
END IF
RETURN
*
9999 FORMAT( ' ******* XERBLA WAS CALLED WITH INFO = ', I6, ' INSTEAD',
$ ' OF ', I2, ' *******' )
9998 FORMAT( ' ******* XERBLA WAS CALLED WITH SRNAME = ', A6, ' INSTE',
$ 'AD OF ', A6, ' *******' )
9997 FORMAT( ' ******* XERBLA WAS CALLED WITH INFO = ', I6,
$ ' *******' )
*
* End of XERBLA
*
END
保存为 testsgbmv.f
$gfortran ./testsgbmv.f
$gdb ./a.out
$b testsgbmv.f:171
分别输入A矩阵的4行数据：
0 0 11 12 13 14
0 15 16 17 18 19
20 21 22 23 24 0
25 26 27 28 0 0
，开始调试。
核心逻辑如下：
//原始带状矩阵B，m=5,n=6, ku=2, kl=1
B(5x6):
|20 15 11 |
|25 21 16 12 |
| 26 22 17 13 |
| 27 23 18 14 |
| 28 24 19 |
带状对齐：
0
0 0
|20 15 11 |
|25 21 16 12 |
| 26 22 17 13 |
| 27 23 18 14 |
| 28 24 19 |
0 0
0
A(4x6):
| 11 12 13 14 |
| 15 16 17 18 19 |
|20 21 22 23 24 |
|25 26 27 28 |
KUP1 = KU + 1
IF (LSAME(TRANS,'N')) THEN
*
* Form y := alpha*A*x + y.
*
JX = KX
IF (INCY.EQ.1) THEN
DO 60 J = 1,N //LL:: A 跟B一样，有N列数字, 第J列
TEMP = ALPHA*X(JX) //LL:: A的同一列，跟X的同一个分量X[JX]相乘，并且累加到Y的不同分量Y[I]上
K = KUP1 - J //LL:: B(1,1) is A(KUP1,1)
DO 50 I = MAX(1,J-KU),MIN(M,J+KL) //LL:: MAX(1,J-KU):B中第J列 1st非零元的行号，MIN(M,J+KL):B中第J列last 非零元的行号;二者给出了本J列对Y向量的作用范围。
Y(I) = Y(I) + TEMP*A(K+I,J) //LL::A(KU+1-J+I, J) is B([本列非零元行号随I从小到大],J) A的同一列，跟X的同一个分量X[JX]相乘，并且累加到Y的不同分量Y[I]上
50 CONTINUE //LL::
JX = JX + INCX
60 CONTINUE
ELSE