| 1 | SUBROUTINE STRSM(SIDE,UPLO,TRANSA,DIAG,M,N,ALPHA,A,LDA,B,LDB) |
|---|
| 2 | * .. Scalar Arguments .. |
|---|
| 3 | REAL ALPHA |
|---|
| 4 | INTEGER LDA,LDB,M,N |
|---|
| 5 | CHARACTER DIAG,SIDE,TRANSA,UPLO |
|---|
| 6 | * .. |
|---|
| 7 | * .. Array Arguments .. |
|---|
| 8 | REAL A(LDA,*),B(LDB,*) |
|---|
| 9 | * .. |
|---|
| 10 | * |
|---|
| 11 | * Purpose |
|---|
| 12 | * ======= |
|---|
| 13 | * |
|---|
| 14 | * STRSM solves one of the matrix equations |
|---|
| 15 | * |
|---|
| 16 | * op( A )*X = alpha*B, or X*op( A ) = alpha*B, |
|---|
| 17 | * |
|---|
| 18 | * where alpha is a scalar, X and B are m by n matrices, A is a unit, or |
|---|
| 19 | * non-unit, upper or lower triangular matrix and op( A ) is one of |
|---|
| 20 | * |
|---|
| 21 | * op( A ) = A or op( A ) = A'. |
|---|
| 22 | * |
|---|
| 23 | * The matrix X is overwritten on B. |
|---|
| 24 | * |
|---|
| 25 | * Arguments |
|---|
| 26 | * ========== |
|---|
| 27 | * |
|---|
| 28 | * SIDE - CHARACTER*1. |
|---|
| 29 | * On entry, SIDE specifies whether op( A ) appears on the left |
|---|
| 30 | * or right of X as follows: |
|---|
| 31 | * |
|---|
| 32 | * SIDE = 'L' or 'l' op( A )*X = alpha*B. |
|---|
| 33 | * |
|---|
| 34 | * SIDE = 'R' or 'r' X*op( A ) = alpha*B. |
|---|
| 35 | * |
|---|
| 36 | * Unchanged on exit. |
|---|
| 37 | * |
|---|
| 38 | * UPLO - CHARACTER*1. |
|---|
| 39 | * On entry, UPLO specifies whether the matrix A is an upper or |
|---|
| 40 | * lower triangular matrix as follows: |
|---|
| 41 | * |
|---|
| 42 | * UPLO = 'U' or 'u' A is an upper triangular matrix. |
|---|
| 43 | * |
|---|
| 44 | * UPLO = 'L' or 'l' A is a lower triangular matrix. |
|---|
| 45 | * |
|---|
| 46 | * Unchanged on exit. |
|---|
| 47 | * |
|---|
| 48 | * TRANSA - CHARACTER*1. |
|---|
| 49 | * On entry, TRANSA specifies the form of op( A ) to be used in |
|---|
| 50 | * the matrix multiplication as follows: |
|---|
| 51 | * |
|---|
| 52 | * TRANSA = 'N' or 'n' op( A ) = A. |
|---|
| 53 | * |
|---|
| 54 | * TRANSA = 'T' or 't' op( A ) = A'. |
|---|
| 55 | * |
|---|
| 56 | * TRANSA = 'C' or 'c' op( A ) = A'. |
|---|
| 57 | * |
|---|
| 58 | * Unchanged on exit. |
|---|
| 59 | * |
|---|
| 60 | * DIAG - CHARACTER*1. |
|---|
| 61 | * On entry, DIAG specifies whether or not A is unit triangular |
|---|
| 62 | * as follows: |
|---|
| 63 | * |
|---|
| 64 | * DIAG = 'U' or 'u' A is assumed to be unit triangular. |
|---|
| 65 | * |
|---|
| 66 | * DIAG = 'N' or 'n' A is not assumed to be unit |
|---|
| 67 | * triangular. |
|---|
| 68 | * |
|---|
| 69 | * Unchanged on exit. |
|---|
| 70 | * |
|---|
| 71 | * M - INTEGER. |
|---|
| 72 | * On entry, M specifies the number of rows of B. M must be at |
|---|
| 73 | * least zero. |
|---|
| 74 | * Unchanged on exit. |
|---|
| 75 | * |
|---|
| 76 | * N - INTEGER. |
|---|
| 77 | * On entry, N specifies the number of columns of B. N must be |
|---|
| 78 | * at least zero. |
|---|
| 79 | * Unchanged on exit. |
|---|
| 80 | * |
|---|
| 81 | * ALPHA - REAL . |
|---|
| 82 | * On entry, ALPHA specifies the scalar alpha. When alpha is |
|---|
| 83 | * zero then A is not referenced and B need not be set before |
|---|
| 84 | * entry. |
|---|
| 85 | * Unchanged on exit. |
|---|
| 86 | * |
|---|
| 87 | * A - REAL array of DIMENSION ( LDA, k ), where k is m |
|---|
| 88 | * when SIDE = 'L' or 'l' and is n when SIDE = 'R' or 'r'. |
|---|
| 89 | * Before entry with UPLO = 'U' or 'u', the leading k by k |
|---|
| 90 | * upper triangular part of the array A must contain the upper |
|---|
| 91 | * triangular matrix and the strictly lower triangular part of |
|---|
| 92 | * A is not referenced. |
|---|
| 93 | * Before entry with UPLO = 'L' or 'l', the leading k by k |
|---|
| 94 | * lower triangular part of the array A must contain the lower |
|---|
| 95 | * triangular matrix and the strictly upper triangular part of |
|---|
| 96 | * A is not referenced. |
|---|
| 97 | * Note that when DIAG = 'U' or 'u', the diagonal elements of |
|---|
| 98 | * A are not referenced either, but are assumed to be unity. |
|---|
| 99 | * Unchanged on exit. |
|---|
| 100 | * |
|---|
| 101 | * LDA - INTEGER. |
|---|
| 102 | * On entry, LDA specifies the first dimension of A as declared |
|---|
| 103 | * in the calling (sub) program. When SIDE = 'L' or 'l' then |
|---|
| 104 | * LDA must be at least max( 1, m ), when SIDE = 'R' or 'r' |
|---|
| 105 | * then LDA must be at least max( 1, n ). |
|---|
| 106 | * Unchanged on exit. |
|---|
| 107 | * |
|---|
| 108 | * B - REAL array of DIMENSION ( LDB, n ). |
|---|
| 109 | * Before entry, the leading m by n part of the array B must |
|---|
| 110 | * contain the right-hand side matrix B, and on exit is |
|---|
| 111 | * overwritten by the solution matrix X. |
|---|
| 112 | * |
|---|
| 113 | * LDB - INTEGER. |
|---|
| 114 | * On entry, LDB specifies the first dimension of B as declared |
|---|
| 115 | * in the calling (sub) program. LDB must be at least |
|---|
| 116 | * max( 1, m ). |
|---|
| 117 | * Unchanged on exit. |
|---|
| 118 | * |
|---|
| 119 | * |
|---|
| 120 | * Level 3 Blas routine. |
|---|
| 121 | * |
|---|
| 122 | * |
|---|
| 123 | * -- Written on 8-February-1989. |
|---|
| 124 | * Jack Dongarra, Argonne National Laboratory. |
|---|
| 125 | * Iain Duff, AERE Harwell. |
|---|
| 126 | * Jeremy Du Croz, Numerical Algorithms Group Ltd. |
|---|
| 127 | * Sven Hammarling, Numerical Algorithms Group Ltd. |
|---|
| 128 | * |
|---|
| 129 | * |
|---|
| 130 | * .. External Functions .. |
|---|
| 131 | LOGICAL LSAME |
|---|
| 132 | EXTERNAL LSAME |
|---|
| 133 | * .. |
|---|
| 134 | * .. External Subroutines .. |
|---|
| 135 | EXTERNAL XERBLA |
|---|
| 136 | * .. |
|---|
| 137 | * .. Intrinsic Functions .. |
|---|
| 138 | INTRINSIC MAX |
|---|
| 139 | * .. |
|---|
| 140 | * .. Local Scalars .. |
|---|
| 141 | REAL TEMP |
|---|
| 142 | INTEGER I,INFO,J,K,NROWA |
|---|
| 143 | LOGICAL LSIDE,NOUNIT,UPPER |
|---|
| 144 | * .. |
|---|
| 145 | * .. Parameters .. |
|---|
| 146 | REAL ONE,ZERO |
|---|
| 147 | PARAMETER (ONE=1.0E+0,ZERO=0.0E+0) |
|---|
| 148 | * .. |
|---|
| 149 | * |
|---|
| 150 | * Test the input parameters. |
|---|
| 151 | * |
|---|
| 152 | LSIDE = LSAME(SIDE,'L') |
|---|
| 153 | IF (LSIDE) THEN |
|---|
| 154 | NROWA = M |
|---|
| 155 | ELSE |
|---|
| 156 | NROWA = N |
|---|
| 157 | END IF |
|---|
| 158 | NOUNIT = LSAME(DIAG,'N') |
|---|
| 159 | UPPER = LSAME(UPLO,'U') |
|---|
| 160 | * |
|---|
| 161 | INFO = 0 |
|---|
| 162 | IF ((.NOT.LSIDE) .AND. (.NOT.LSAME(SIDE,'R'))) THEN |
|---|
| 163 | INFO = 1 |
|---|
| 164 | ELSE IF ((.NOT.UPPER) .AND. (.NOT.LSAME(UPLO,'L'))) THEN |
|---|
| 165 | INFO = 2 |
|---|
| 166 | ELSE IF ((.NOT.LSAME(TRANSA,'N')) .AND. |
|---|
| 167 | + (.NOT.LSAME(TRANSA,'T')) .AND. |
|---|
| 168 | + (.NOT.LSAME(TRANSA,'C'))) THEN |
|---|
| 169 | INFO = 3 |
|---|
| 170 | ELSE IF ((.NOT.LSAME(DIAG,'U')) .AND. (.NOT.LSAME(DIAG,'N'))) THEN |
|---|
| 171 | INFO = 4 |
|---|
| 172 | ELSE IF (M.LT.0) THEN |
|---|
| 173 | INFO = 5 |
|---|
| 174 | ELSE IF (N.LT.0) THEN |
|---|
| 175 | INFO = 6 |
|---|
| 176 | ELSE IF (LDA.LT.MAX(1,NROWA)) THEN |
|---|
| 177 | INFO = 9 |
|---|
| 178 | ELSE IF (LDB.LT.MAX(1,M)) THEN |
|---|
| 179 | INFO = 11 |
|---|
| 180 | END IF |
|---|
| 181 | IF (INFO.NE.0) THEN |
|---|
| 182 | CALL XERBLA('STRSM ',INFO) |
|---|
| 183 | RETURN |
|---|
| 184 | END IF |
|---|
| 185 | * |
|---|
| 186 | * Quick return if possible. |
|---|
| 187 | * |
|---|
| 188 | IF (M.EQ.0 .OR. N.EQ.0) RETURN |
|---|
| 189 | * |
|---|
| 190 | * And when alpha.eq.zero. |
|---|
| 191 | * |
|---|
| 192 | IF (ALPHA.EQ.ZERO) THEN |
|---|
| 193 | DO 20 J = 1,N |
|---|
| 194 | DO 10 I = 1,M |
|---|
| 195 | B(I,J) = ZERO |
|---|
| 196 | 10 CONTINUE |
|---|
| 197 | 20 CONTINUE |
|---|
| 198 | RETURN |
|---|
| 199 | END IF |
|---|
| 200 | * |
|---|
| 201 | * Start the operations. |
|---|
| 202 | * |
|---|
| 203 | IF (LSIDE) THEN |
|---|
| 204 | IF (LSAME(TRANSA,'N')) THEN |
|---|
| 205 | * |
|---|
| 206 | * Form B := alpha*inv( A )*B. |
|---|
| 207 | * |
|---|
| 208 | IF (UPPER) THEN |
|---|
| 209 | DO 60 J = 1,N |
|---|
| 210 | IF (ALPHA.NE.ONE) THEN |
|---|
| 211 | DO 30 I = 1,M |
|---|
| 212 | B(I,J) = ALPHA*B(I,J) |
|---|
| 213 | 30 CONTINUE |
|---|
| 214 | END IF |
|---|
| 215 | DO 50 K = M,1,-1 |
|---|
| 216 | IF (B(K,J).NE.ZERO) THEN |
|---|
| 217 | IF (NOUNIT) B(K,J) = B(K,J)/A(K,K) |
|---|
| 218 | DO 40 I = 1,K - 1 |
|---|
| 219 | B(I,J) = B(I,J) - B(K,J)*A(I,K) |
|---|
| 220 | 40 CONTINUE |
|---|
| 221 | END IF |
|---|
| 222 | 50 CONTINUE |
|---|
| 223 | 60 CONTINUE |
|---|
| 224 | ELSE |
|---|
| 225 | DO 100 J = 1,N |
|---|
| 226 | IF (ALPHA.NE.ONE) THEN |
|---|
| 227 | DO 70 I = 1,M |
|---|
| 228 | B(I,J) = ALPHA*B(I,J) |
|---|
| 229 | 70 CONTINUE |
|---|
| 230 | END IF |
|---|
| 231 | DO 90 K = 1,M |
|---|
| 232 | IF (B(K,J).NE.ZERO) THEN |
|---|
| 233 | IF (NOUNIT) B(K,J) = B(K,J)/A(K,K) |
|---|
| 234 | DO 80 I = K + 1,M |
|---|
| 235 | B(I,J) = B(I,J) - B(K,J)*A(I,K) |
|---|
| 236 | 80 CONTINUE |
|---|
| 237 | END IF |
|---|
| 238 | 90 CONTINUE |
|---|
| 239 | 100 CONTINUE |
|---|
| 240 | END IF |
|---|
| 241 | ELSE |
|---|
| 242 | * |
|---|
| 243 | * Form B := alpha*inv( A' )*B. |
|---|
| 244 | * |
|---|
| 245 | IF (UPPER) THEN |
|---|
| 246 | DO 130 J = 1,N |
|---|
| 247 | DO 120 I = 1,M |
|---|
| 248 | TEMP = ALPHA*B(I,J) |
|---|
| 249 | DO 110 K = 1,I - 1 |
|---|
| 250 | TEMP = TEMP - A(K,I)*B(K,J) |
|---|
| 251 | 110 CONTINUE |
|---|
| 252 | IF (NOUNIT) TEMP = TEMP/A(I,I) |
|---|
| 253 | B(I,J) = TEMP |
|---|
| 254 | 120 CONTINUE |
|---|
| 255 | 130 CONTINUE |
|---|
| 256 | ELSE |
|---|
| 257 | DO 160 J = 1,N |
|---|
| 258 | DO 150 I = M,1,-1 |
|---|
| 259 | TEMP = ALPHA*B(I,J) |
|---|
| 260 | DO 140 K = I + 1,M |
|---|
| 261 | TEMP = TEMP - A(K,I)*B(K,J) |
|---|
| 262 | 140 CONTINUE |
|---|
| 263 | IF (NOUNIT) TEMP = TEMP/A(I,I) |
|---|
| 264 | B(I,J) = TEMP |
|---|
| 265 | 150 CONTINUE |
|---|
| 266 | 160 CONTINUE |
|---|
| 267 | END IF |
|---|
| 268 | END IF |
|---|
| 269 | ELSE |
|---|
| 270 | IF (LSAME(TRANSA,'N')) THEN |
|---|
| 271 | * |
|---|
| 272 | * Form B := alpha*B*inv( A ). |
|---|
| 273 | * |
|---|
| 274 | IF (UPPER) THEN |
|---|
| 275 | DO 210 J = 1,N |
|---|
| 276 | IF (ALPHA.NE.ONE) THEN |
|---|
| 277 | DO 170 I = 1,M |
|---|
| 278 | B(I,J) = ALPHA*B(I,J) |
|---|
| 279 | 170 CONTINUE |
|---|
| 280 | END IF |
|---|
| 281 | DO 190 K = 1,J - 1 |
|---|
| 282 | IF (A(K,J).NE.ZERO) THEN |
|---|
| 283 | DO 180 I = 1,M |
|---|
| 284 | B(I,J) = B(I,J) - A(K,J)*B(I,K) |
|---|
| 285 | 180 CONTINUE |
|---|
| 286 | END IF |
|---|
| 287 | 190 CONTINUE |
|---|
| 288 | IF (NOUNIT) THEN |
|---|
| 289 | TEMP = ONE/A(J,J) |
|---|
| 290 | DO 200 I = 1,M |
|---|
| 291 | B(I,J) = TEMP*B(I,J) |
|---|
| 292 | 200 CONTINUE |
|---|
| 293 | END IF |
|---|
| 294 | 210 CONTINUE |
|---|
| 295 | ELSE |
|---|
| 296 | DO 260 J = N,1,-1 |
|---|
| 297 | IF (ALPHA.NE.ONE) THEN |
|---|
| 298 | DO 220 I = 1,M |
|---|
| 299 | B(I,J) = ALPHA*B(I,J) |
|---|
| 300 | 220 CONTINUE |
|---|
| 301 | END IF |
|---|
| 302 | DO 240 K = J + 1,N |
|---|
| 303 | IF (A(K,J).NE.ZERO) THEN |
|---|
| 304 | DO 230 I = 1,M |
|---|
| 305 | B(I,J) = B(I,J) - A(K,J)*B(I,K) |
|---|
| 306 | 230 CONTINUE |
|---|
| 307 | END IF |
|---|
| 308 | 240 CONTINUE |
|---|
| 309 | IF (NOUNIT) THEN |
|---|
| 310 | TEMP = ONE/A(J,J) |
|---|
| 311 | DO 250 I = 1,M |
|---|
| 312 | B(I,J) = TEMP*B(I,J) |
|---|
| 313 | 250 CONTINUE |
|---|
| 314 | END IF |
|---|
| 315 | 260 CONTINUE |
|---|
| 316 | END IF |
|---|
| 317 | ELSE |
|---|
| 318 | * |
|---|
| 319 | * Form B := alpha*B*inv( A' ). |
|---|
| 320 | * |
|---|
| 321 | IF (UPPER) THEN |
|---|
| 322 | DO 310 K = N,1,-1 |
|---|
| 323 | IF (NOUNIT) THEN |
|---|
| 324 | TEMP = ONE/A(K,K) |
|---|
| 325 | DO 270 I = 1,M |
|---|
| 326 | B(I,K) = TEMP*B(I,K) |
|---|
| 327 | 270 CONTINUE |
|---|
| 328 | END IF |
|---|
| 329 | DO 290 J = 1,K - 1 |
|---|
| 330 | IF (A(J,K).NE.ZERO) THEN |
|---|
| 331 | TEMP = A(J,K) |
|---|
| 332 | DO 280 I = 1,M |
|---|
| 333 | B(I,J) = B(I,J) - TEMP*B(I,K) |
|---|
| 334 | 280 CONTINUE |
|---|
| 335 | END IF |
|---|
| 336 | 290 CONTINUE |
|---|
| 337 | IF (ALPHA.NE.ONE) THEN |
|---|
| 338 | DO 300 I = 1,M |
|---|
| 339 | B(I,K) = ALPHA*B(I,K) |
|---|
| 340 | 300 CONTINUE |
|---|
| 341 | END IF |
|---|
| 342 | 310 CONTINUE |
|---|
| 343 | ELSE |
|---|
| 344 | DO 360 K = 1,N |
|---|
| 345 | IF (NOUNIT) THEN |
|---|
| 346 | TEMP = ONE/A(K,K) |
|---|
| 347 | DO 320 I = 1,M |
|---|
| 348 | B(I,K) = TEMP*B(I,K) |
|---|
| 349 | 320 CONTINUE |
|---|
| 350 | END IF |
|---|
| 351 | DO 340 J = K + 1,N |
|---|
| 352 | IF (A(J,K).NE.ZERO) THEN |
|---|
| 353 | TEMP = A(J,K) |
|---|
| 354 | DO 330 I = 1,M |
|---|
| 355 | B(I,J) = B(I,J) - TEMP*B(I,K) |
|---|
| 356 | 330 CONTINUE |
|---|
| 357 | END IF |
|---|
| 358 | 340 CONTINUE |
|---|
| 359 | IF (ALPHA.NE.ONE) THEN |
|---|
| 360 | DO 350 I = 1,M |
|---|
| 361 | B(I,K) = ALPHA*B(I,K) |
|---|
| 362 | 350 CONTINUE |
|---|
| 363 | END IF |
|---|
| 364 | 360 CONTINUE |
|---|
| 365 | END IF |
|---|
| 366 | END IF |
|---|
| 367 | END IF |
|---|
| 368 | * |
|---|
| 369 | RETURN |
|---|
| 370 | * |
|---|
| 371 | * End of STRSM . |
|---|
| 372 | * |
|---|
| 373 | END |
|---|
