Annotation of rpl/lapack/blas/dsymm.f, revision 1.1
1.1 ! bertrand 1: SUBROUTINE DSYMM(SIDE,UPLO,M,N,ALPHA,A,LDA,B,LDB,BETA,C,LDC)
! 2: * .. Scalar Arguments ..
! 3: DOUBLE PRECISION ALPHA,BETA
! 4: INTEGER LDA,LDB,LDC,M,N
! 5: CHARACTER SIDE,UPLO
! 6: * ..
! 7: * .. Array Arguments ..
! 8: DOUBLE PRECISION A(LDA,*),B(LDB,*),C(LDC,*)
! 9: * ..
! 10: *
! 11: * Purpose
! 12: * =======
! 13: *
! 14: * DSYMM performs one of the matrix-matrix operations
! 15: *
! 16: * C := alpha*A*B + beta*C,
! 17: *
! 18: * or
! 19: *
! 20: * C := alpha*B*A + beta*C,
! 21: *
! 22: * where alpha and beta are scalars, A is a symmetric matrix and B and
! 23: * C are m by n matrices.
! 24: *
! 25: * Arguments
! 26: * ==========
! 27: *
! 28: * SIDE - CHARACTER*1.
! 29: * On entry, SIDE specifies whether the symmetric matrix A
! 30: * appears on the left or right in the operation as follows:
! 31: *
! 32: * SIDE = 'L' or 'l' C := alpha*A*B + beta*C,
! 33: *
! 34: * SIDE = 'R' or 'r' C := alpha*B*A + beta*C,
! 35: *
! 36: * Unchanged on exit.
! 37: *
! 38: * UPLO - CHARACTER*1.
! 39: * On entry, UPLO specifies whether the upper or lower
! 40: * triangular part of the symmetric matrix A is to be
! 41: * referenced as follows:
! 42: *
! 43: * UPLO = 'U' or 'u' Only the upper triangular part of the
! 44: * symmetric matrix is to be referenced.
! 45: *
! 46: * UPLO = 'L' or 'l' Only the lower triangular part of the
! 47: * symmetric matrix is to be referenced.
! 48: *
! 49: * Unchanged on exit.
! 50: *
! 51: * M - INTEGER.
! 52: * On entry, M specifies the number of rows of the matrix C.
! 53: * M must be at least zero.
! 54: * Unchanged on exit.
! 55: *
! 56: * N - INTEGER.
! 57: * On entry, N specifies the number of columns of the matrix C.
! 58: * N must be at least zero.
! 59: * Unchanged on exit.
! 60: *
! 61: * ALPHA - DOUBLE PRECISION.
! 62: * On entry, ALPHA specifies the scalar alpha.
! 63: * Unchanged on exit.
! 64: *
! 65: * A - DOUBLE PRECISION array of DIMENSION ( LDA, ka ), where ka is
! 66: * m when SIDE = 'L' or 'l' and is n otherwise.
! 67: * Before entry with SIDE = 'L' or 'l', the m by m part of
! 68: * the array A must contain the symmetric matrix, such that
! 69: * when UPLO = 'U' or 'u', the leading m by m upper triangular
! 70: * part of the array A must contain the upper triangular part
! 71: * of the symmetric matrix and the strictly lower triangular
! 72: * part of A is not referenced, and when UPLO = 'L' or 'l',
! 73: * the leading m by m lower triangular part of the array A
! 74: * must contain the lower triangular part of the symmetric
! 75: * matrix and the strictly upper triangular part of A is not
! 76: * referenced.
! 77: * Before entry with SIDE = 'R' or 'r', the n by n part of
! 78: * the array A must contain the symmetric matrix, such that
! 79: * when UPLO = 'U' or 'u', the leading n by n upper triangular
! 80: * part of the array A must contain the upper triangular part
! 81: * of the symmetric matrix and the strictly lower triangular
! 82: * part of A is not referenced, and when UPLO = 'L' or 'l',
! 83: * the leading n by n lower triangular part of the array A
! 84: * must contain the lower triangular part of the symmetric
! 85: * matrix and the strictly upper triangular part of A is not
! 86: * referenced.
! 87: * Unchanged on exit.
! 88: *
! 89: * LDA - INTEGER.
! 90: * On entry, LDA specifies the first dimension of A as declared
! 91: * in the calling (sub) program. When SIDE = 'L' or 'l' then
! 92: * LDA must be at least max( 1, m ), otherwise LDA must be at
! 93: * least max( 1, n ).
! 94: * Unchanged on exit.
! 95: *
! 96: * B - DOUBLE PRECISION array of DIMENSION ( LDB, n ).
! 97: * Before entry, the leading m by n part of the array B must
! 98: * contain the matrix B.
! 99: * Unchanged on exit.
! 100: *
! 101: * LDB - INTEGER.
! 102: * On entry, LDB specifies the first dimension of B as declared
! 103: * in the calling (sub) program. LDB must be at least
! 104: * max( 1, m ).
! 105: * Unchanged on exit.
! 106: *
! 107: * BETA - DOUBLE PRECISION.
! 108: * On entry, BETA specifies the scalar beta. When BETA is
! 109: * supplied as zero then C need not be set on input.
! 110: * Unchanged on exit.
! 111: *
! 112: * C - DOUBLE PRECISION array of DIMENSION ( LDC, n ).
! 113: * Before entry, the leading m by n part of the array C must
! 114: * contain the matrix C, except when beta is zero, in which
! 115: * case C need not be set on entry.
! 116: * On exit, the array C is overwritten by the m by n updated
! 117: * matrix.
! 118: *
! 119: * LDC - INTEGER.
! 120: * On entry, LDC specifies the first dimension of C as declared
! 121: * in the calling (sub) program. LDC must be at least
! 122: * max( 1, m ).
! 123: * Unchanged on exit.
! 124: *
! 125: * Further Details
! 126: * ===============
! 127: *
! 128: * Level 3 Blas routine.
! 129: *
! 130: * -- Written on 8-February-1989.
! 131: * Jack Dongarra, Argonne National Laboratory.
! 132: * Iain Duff, AERE Harwell.
! 133: * Jeremy Du Croz, Numerical Algorithms Group Ltd.
! 134: * Sven Hammarling, Numerical Algorithms Group Ltd.
! 135: *
! 136: * =====================================================================
! 137: *
! 138: * .. External Functions ..
! 139: LOGICAL LSAME
! 140: EXTERNAL LSAME
! 141: * ..
! 142: * .. External Subroutines ..
! 143: EXTERNAL XERBLA
! 144: * ..
! 145: * .. Intrinsic Functions ..
! 146: INTRINSIC MAX
! 147: * ..
! 148: * .. Local Scalars ..
! 149: DOUBLE PRECISION TEMP1,TEMP2
! 150: INTEGER I,INFO,J,K,NROWA
! 151: LOGICAL UPPER
! 152: * ..
! 153: * .. Parameters ..
! 154: DOUBLE PRECISION ONE,ZERO
! 155: PARAMETER (ONE=1.0D+0,ZERO=0.0D+0)
! 156: * ..
! 157: *
! 158: * Set NROWA as the number of rows of A.
! 159: *
! 160: IF (LSAME(SIDE,'L')) THEN
! 161: NROWA = M
! 162: ELSE
! 163: NROWA = N
! 164: END IF
! 165: UPPER = LSAME(UPLO,'U')
! 166: *
! 167: * Test the input parameters.
! 168: *
! 169: INFO = 0
! 170: IF ((.NOT.LSAME(SIDE,'L')) .AND. (.NOT.LSAME(SIDE,'R'))) THEN
! 171: INFO = 1
! 172: ELSE IF ((.NOT.UPPER) .AND. (.NOT.LSAME(UPLO,'L'))) THEN
! 173: INFO = 2
! 174: ELSE IF (M.LT.0) THEN
! 175: INFO = 3
! 176: ELSE IF (N.LT.0) THEN
! 177: INFO = 4
! 178: ELSE IF (LDA.LT.MAX(1,NROWA)) THEN
! 179: INFO = 7
! 180: ELSE IF (LDB.LT.MAX(1,M)) THEN
! 181: INFO = 9
! 182: ELSE IF (LDC.LT.MAX(1,M)) THEN
! 183: INFO = 12
! 184: END IF
! 185: IF (INFO.NE.0) THEN
! 186: CALL XERBLA('DSYMM ',INFO)
! 187: RETURN
! 188: END IF
! 189: *
! 190: * Quick return if possible.
! 191: *
! 192: IF ((M.EQ.0) .OR. (N.EQ.0) .OR.
! 193: + ((ALPHA.EQ.ZERO).AND. (BETA.EQ.ONE))) RETURN
! 194: *
! 195: * And when alpha.eq.zero.
! 196: *
! 197: IF (ALPHA.EQ.ZERO) THEN
! 198: IF (BETA.EQ.ZERO) THEN
! 199: DO 20 J = 1,N
! 200: DO 10 I = 1,M
! 201: C(I,J) = ZERO
! 202: 10 CONTINUE
! 203: 20 CONTINUE
! 204: ELSE
! 205: DO 40 J = 1,N
! 206: DO 30 I = 1,M
! 207: C(I,J) = BETA*C(I,J)
! 208: 30 CONTINUE
! 209: 40 CONTINUE
! 210: END IF
! 211: RETURN
! 212: END IF
! 213: *
! 214: * Start the operations.
! 215: *
! 216: IF (LSAME(SIDE,'L')) THEN
! 217: *
! 218: * Form C := alpha*A*B + beta*C.
! 219: *
! 220: IF (UPPER) THEN
! 221: DO 70 J = 1,N
! 222: DO 60 I = 1,M
! 223: TEMP1 = ALPHA*B(I,J)
! 224: TEMP2 = ZERO
! 225: DO 50 K = 1,I - 1
! 226: C(K,J) = C(K,J) + TEMP1*A(K,I)
! 227: TEMP2 = TEMP2 + B(K,J)*A(K,I)
! 228: 50 CONTINUE
! 229: IF (BETA.EQ.ZERO) THEN
! 230: C(I,J) = TEMP1*A(I,I) + ALPHA*TEMP2
! 231: ELSE
! 232: C(I,J) = BETA*C(I,J) + TEMP1*A(I,I) +
! 233: + ALPHA*TEMP2
! 234: END IF
! 235: 60 CONTINUE
! 236: 70 CONTINUE
! 237: ELSE
! 238: DO 100 J = 1,N
! 239: DO 90 I = M,1,-1
! 240: TEMP1 = ALPHA*B(I,J)
! 241: TEMP2 = ZERO
! 242: DO 80 K = I + 1,M
! 243: C(K,J) = C(K,J) + TEMP1*A(K,I)
! 244: TEMP2 = TEMP2 + B(K,J)*A(K,I)
! 245: 80 CONTINUE
! 246: IF (BETA.EQ.ZERO) THEN
! 247: C(I,J) = TEMP1*A(I,I) + ALPHA*TEMP2
! 248: ELSE
! 249: C(I,J) = BETA*C(I,J) + TEMP1*A(I,I) +
! 250: + ALPHA*TEMP2
! 251: END IF
! 252: 90 CONTINUE
! 253: 100 CONTINUE
! 254: END IF
! 255: ELSE
! 256: *
! 257: * Form C := alpha*B*A + beta*C.
! 258: *
! 259: DO 170 J = 1,N
! 260: TEMP1 = ALPHA*A(J,J)
! 261: IF (BETA.EQ.ZERO) THEN
! 262: DO 110 I = 1,M
! 263: C(I,J) = TEMP1*B(I,J)
! 264: 110 CONTINUE
! 265: ELSE
! 266: DO 120 I = 1,M
! 267: C(I,J) = BETA*C(I,J) + TEMP1*B(I,J)
! 268: 120 CONTINUE
! 269: END IF
! 270: DO 140 K = 1,J - 1
! 271: IF (UPPER) THEN
! 272: TEMP1 = ALPHA*A(K,J)
! 273: ELSE
! 274: TEMP1 = ALPHA*A(J,K)
! 275: END IF
! 276: DO 130 I = 1,M
! 277: C(I,J) = C(I,J) + TEMP1*B(I,K)
! 278: 130 CONTINUE
! 279: 140 CONTINUE
! 280: DO 160 K = J + 1,N
! 281: IF (UPPER) THEN
! 282: TEMP1 = ALPHA*A(J,K)
! 283: ELSE
! 284: TEMP1 = ALPHA*A(K,J)
! 285: END IF
! 286: DO 150 I = 1,M
! 287: C(I,J) = C(I,J) + TEMP1*B(I,K)
! 288: 150 CONTINUE
! 289: 160 CONTINUE
! 290: 170 CONTINUE
! 291: END IF
! 292: *
! 293: RETURN
! 294: *
! 295: * End of DSYMM .
! 296: *
! 297: END
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