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LAPACK 3.3.1
Linear Algebra PACKage
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LAPACK 3.3.1
Linear Algebra PACKage
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00001 SUBROUTINE DGEMM(TRANSA,TRANSB,M,N,K,ALPHA,A,LDA,B,LDB,BETA,C,LDC) 00002 * .. Scalar Arguments .. 00003 DOUBLE PRECISION ALPHA,BETA 00004 INTEGER K,LDA,LDB,LDC,M,N 00005 CHARACTER TRANSA,TRANSB 00006 * .. 00007 * .. Array Arguments .. 00008 DOUBLE PRECISION A(LDA,*),B(LDB,*),C(LDC,*) 00009 * .. 00010 * 00011 * Purpose 00012 * ======= 00013 * 00014 * DGEMM performs one of the matrix-matrix operations 00015 * 00016 * C := alpha*op( A )*op( B ) + beta*C, 00017 * 00018 * where op( X ) is one of 00019 * 00020 * op( X ) = X or op( X ) = X**T, 00021 * 00022 * alpha and beta are scalars, and A, B and C are matrices, with op( A ) 00023 * an m by k matrix, op( B ) a k by n matrix and C an m by n matrix. 00024 * 00025 * Arguments 00026 * ========== 00027 * 00028 * TRANSA - CHARACTER*1. 00029 * On entry, TRANSA specifies the form of op( A ) to be used in 00030 * the matrix multiplication as follows: 00031 * 00032 * TRANSA = 'N' or 'n', op( A ) = A. 00033 * 00034 * TRANSA = 'T' or 't', op( A ) = A**T. 00035 * 00036 * TRANSA = 'C' or 'c', op( A ) = A**T. 00037 * 00038 * Unchanged on exit. 00039 * 00040 * TRANSB - CHARACTER*1. 00041 * On entry, TRANSB specifies the form of op( B ) to be used in 00042 * the matrix multiplication as follows: 00043 * 00044 * TRANSB = 'N' or 'n', op( B ) = B. 00045 * 00046 * TRANSB = 'T' or 't', op( B ) = B**T. 00047 * 00048 * TRANSB = 'C' or 'c', op( B ) = B**T. 00049 * 00050 * Unchanged on exit. 00051 * 00052 * M - INTEGER. 00053 * On entry, M specifies the number of rows of the matrix 00054 * op( A ) and of the matrix C. M must be at least zero. 00055 * Unchanged on exit. 00056 * 00057 * N - INTEGER. 00058 * On entry, N specifies the number of columns of the matrix 00059 * op( B ) and the number of columns of the matrix C. N must be 00060 * at least zero. 00061 * Unchanged on exit. 00062 * 00063 * K - INTEGER. 00064 * On entry, K specifies the number of columns of the matrix 00065 * op( A ) and the number of rows of the matrix op( B ). K must 00066 * be at least zero. 00067 * Unchanged on exit. 00068 * 00069 * ALPHA - DOUBLE PRECISION. 00070 * On entry, ALPHA specifies the scalar alpha. 00071 * Unchanged on exit. 00072 * 00073 * A - DOUBLE PRECISION array of DIMENSION ( LDA, ka ), where ka is 00074 * k when TRANSA = 'N' or 'n', and is m otherwise. 00075 * Before entry with TRANSA = 'N' or 'n', the leading m by k 00076 * part of the array A must contain the matrix A, otherwise 00077 * the leading k by m part of the array A must contain the 00078 * matrix A. 00079 * Unchanged on exit. 00080 * 00081 * LDA - INTEGER. 00082 * On entry, LDA specifies the first dimension of A as declared 00083 * in the calling (sub) program. When TRANSA = 'N' or 'n' then 00084 * LDA must be at least max( 1, m ), otherwise LDA must be at 00085 * least max( 1, k ). 00086 * Unchanged on exit. 00087 * 00088 * B - DOUBLE PRECISION array of DIMENSION ( LDB, kb ), where kb is 00089 * n when TRANSB = 'N' or 'n', and is k otherwise. 00090 * Before entry with TRANSB = 'N' or 'n', the leading k by n 00091 * part of the array B must contain the matrix B, otherwise 00092 * the leading n by k part of the array B must contain the 00093 * matrix B. 00094 * Unchanged on exit. 00095 * 00096 * LDB - INTEGER. 00097 * On entry, LDB specifies the first dimension of B as declared 00098 * in the calling (sub) program. When TRANSB = 'N' or 'n' then 00099 * LDB must be at least max( 1, k ), otherwise LDB must be at 00100 * least max( 1, n ). 00101 * Unchanged on exit. 00102 * 00103 * BETA - DOUBLE PRECISION. 00104 * On entry, BETA specifies the scalar beta. When BETA is 00105 * supplied as zero then C need not be set on input. 00106 * Unchanged on exit. 00107 * 00108 * C - DOUBLE PRECISION array of DIMENSION ( LDC, n ). 00109 * Before entry, the leading m by n part of the array C must 00110 * contain the matrix C, except when beta is zero, in which 00111 * case C need not be set on entry. 00112 * On exit, the array C is overwritten by the m by n matrix 00113 * ( alpha*op( A )*op( B ) + beta*C ). 00114 * 00115 * LDC - INTEGER. 00116 * On entry, LDC specifies the first dimension of C as declared 00117 * in the calling (sub) program. LDC must be at least 00118 * max( 1, m ). 00119 * Unchanged on exit. 00120 * 00121 * Further Details 00122 * =============== 00123 * 00124 * Level 3 Blas routine. 00125 * 00126 * -- Written on 8-February-1989. 00127 * Jack Dongarra, Argonne National Laboratory. 00128 * Iain Duff, AERE Harwell. 00129 * Jeremy Du Croz, Numerical Algorithms Group Ltd. 00130 * Sven Hammarling, Numerical Algorithms Group Ltd. 00131 * 00132 * ===================================================================== 00133 * 00134 * .. External Functions .. 00135 LOGICAL LSAME 00136 EXTERNAL LSAME 00137 * .. 00138 * .. External Subroutines .. 00139 EXTERNAL XERBLA 00140 * .. 00141 * .. Intrinsic Functions .. 00142 INTRINSIC MAX 00143 * .. 00144 * .. Local Scalars .. 00145 DOUBLE PRECISION TEMP 00146 INTEGER I,INFO,J,L,NCOLA,NROWA,NROWB 00147 LOGICAL NOTA,NOTB 00148 * .. 00149 * .. Parameters .. 00150 DOUBLE PRECISION ONE,ZERO 00151 PARAMETER (ONE=1.0D+0,ZERO=0.0D+0) 00152 * .. 00153 * 00154 * Set NOTA and NOTB as true if A and B respectively are not 00155 * transposed and set NROWA, NCOLA and NROWB as the number of rows 00156 * and columns of A and the number of rows of B respectively. 00157 * 00158 NOTA = LSAME(TRANSA,'N') 00159 NOTB = LSAME(TRANSB,'N') 00160 IF (NOTA) THEN 00161 NROWA = M 00162 NCOLA = K 00163 ELSE 00164 NROWA = K 00165 NCOLA = M 00166 END IF 00167 IF (NOTB) THEN 00168 NROWB = K 00169 ELSE 00170 NROWB = N 00171 END IF 00172 * 00173 * Test the input parameters. 00174 * 00175 INFO = 0 00176 IF ((.NOT.NOTA) .AND. (.NOT.LSAME(TRANSA,'C')) .AND. 00177 + (.NOT.LSAME(TRANSA,'T'))) THEN 00178 INFO = 1 00179 ELSE IF ((.NOT.NOTB) .AND. (.NOT.LSAME(TRANSB,'C')) .AND. 00180 + (.NOT.LSAME(TRANSB,'T'))) THEN 00181 INFO = 2 00182 ELSE IF (M.LT.0) THEN 00183 INFO = 3 00184 ELSE IF (N.LT.0) THEN 00185 INFO = 4 00186 ELSE IF (K.LT.0) THEN 00187 INFO = 5 00188 ELSE IF (LDA.LT.MAX(1,NROWA)) THEN 00189 INFO = 8 00190 ELSE IF (LDB.LT.MAX(1,NROWB)) THEN 00191 INFO = 10 00192 ELSE IF (LDC.LT.MAX(1,M)) THEN 00193 INFO = 13 00194 END IF 00195 IF (INFO.NE.0) THEN 00196 CALL XERBLA('DGEMM ',INFO) 00197 RETURN 00198 END IF 00199 * 00200 * Quick return if possible. 00201 * 00202 IF ((M.EQ.0) .OR. (N.EQ.0) .OR. 00203 + (((ALPHA.EQ.ZERO).OR. (K.EQ.0)).AND. (BETA.EQ.ONE))) RETURN 00204 * 00205 * And if alpha.eq.zero. 00206 * 00207 IF (ALPHA.EQ.ZERO) THEN 00208 IF (BETA.EQ.ZERO) THEN 00209 DO 20 J = 1,N 00210 DO 10 I = 1,M 00211 C(I,J) = ZERO 00212 10 CONTINUE 00213 20 CONTINUE 00214 ELSE 00215 DO 40 J = 1,N 00216 DO 30 I = 1,M 00217 C(I,J) = BETA*C(I,J) 00218 30 CONTINUE 00219 40 CONTINUE 00220 END IF 00221 RETURN 00222 END IF 00223 * 00224 * Start the operations. 00225 * 00226 IF (NOTB) THEN 00227 IF (NOTA) THEN 00228 * 00229 * Form C := alpha*A*B + beta*C. 00230 * 00231 DO 90 J = 1,N 00232 IF (BETA.EQ.ZERO) THEN 00233 DO 50 I = 1,M 00234 C(I,J) = ZERO 00235 50 CONTINUE 00236 ELSE IF (BETA.NE.ONE) THEN 00237 DO 60 I = 1,M 00238 C(I,J) = BETA*C(I,J) 00239 60 CONTINUE 00240 END IF 00241 DO 80 L = 1,K 00242 IF (B(L,J).NE.ZERO) THEN 00243 TEMP = ALPHA*B(L,J) 00244 DO 70 I = 1,M 00245 C(I,J) = C(I,J) + TEMP*A(I,L) 00246 70 CONTINUE 00247 END IF 00248 80 CONTINUE 00249 90 CONTINUE 00250 ELSE 00251 * 00252 * Form C := alpha*A**T*B + beta*C 00253 * 00254 DO 120 J = 1,N 00255 DO 110 I = 1,M 00256 TEMP = ZERO 00257 DO 100 L = 1,K 00258 TEMP = TEMP + A(L,I)*B(L,J) 00259 100 CONTINUE 00260 IF (BETA.EQ.ZERO) THEN 00261 C(I,J) = ALPHA*TEMP 00262 ELSE 00263 C(I,J) = ALPHA*TEMP + BETA*C(I,J) 00264 END IF 00265 110 CONTINUE 00266 120 CONTINUE 00267 END IF 00268 ELSE 00269 IF (NOTA) THEN 00270 * 00271 * Form C := alpha*A*B**T + beta*C 00272 * 00273 DO 170 J = 1,N 00274 IF (BETA.EQ.ZERO) THEN 00275 DO 130 I = 1,M 00276 C(I,J) = ZERO 00277 130 CONTINUE 00278 ELSE IF (BETA.NE.ONE) THEN 00279 DO 140 I = 1,M 00280 C(I,J) = BETA*C(I,J) 00281 140 CONTINUE 00282 END IF 00283 DO 160 L = 1,K 00284 IF (B(J,L).NE.ZERO) THEN 00285 TEMP = ALPHA*B(J,L) 00286 DO 150 I = 1,M 00287 C(I,J) = C(I,J) + TEMP*A(I,L) 00288 150 CONTINUE 00289 END IF 00290 160 CONTINUE 00291 170 CONTINUE 00292 ELSE 00293 * 00294 * Form C := alpha*A**T*B**T + beta*C 00295 * 00296 DO 200 J = 1,N 00297 DO 190 I = 1,M 00298 TEMP = ZERO 00299 DO 180 L = 1,K 00300 TEMP = TEMP + A(L,I)*B(J,L) 00301 180 CONTINUE 00302 IF (BETA.EQ.ZERO) THEN 00303 C(I,J) = ALPHA*TEMP 00304 ELSE 00305 C(I,J) = ALPHA*TEMP + BETA*C(I,J) 00306 END IF 00307 190 CONTINUE 00308 200 CONTINUE 00309 END IF 00310 END IF 00311 * 00312 RETURN 00313 * 00314 * End of DGEMM . 00315 * 00316 END
1.7.3 
