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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 INTEGER FUNCTION ILAENV( ISPEC, NAME, OPTS, N1, N2, N3, 00002 $ N4 ) 00003 * 00004 * -- LAPACK auxiliary routine (version 3.1) -- 00005 * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. 00006 * November 2006 00007 * 00008 * .. Scalar Arguments .. 00009 CHARACTER*( * ) NAME, OPTS 00010 INTEGER ISPEC, N1, N2, N3, N4 00011 * .. 00012 * 00013 * Purpose 00014 * ======= 00015 * 00016 * ILAENV returns problem-dependent parameters for the local 00017 * environment. See ISPEC for a description of the parameters. 00018 * 00019 * In this version, the problem-dependent parameters are contained in 00020 * the integer array IPARMS in the common block CLAENV and the value 00021 * with index ISPEC is copied to ILAENV. This version of ILAENV is 00022 * to be used in conjunction with XLAENV in TESTING and TIMING. 00023 * 00024 * Arguments 00025 * ========= 00026 * 00027 * ISPEC (input) INTEGER 00028 * Specifies the parameter to be returned as the value of 00029 * ILAENV. 00030 * = 1: the optimal blocksize; if this value is 1, an unblocked 00031 * algorithm will give the best performance. 00032 * = 2: the minimum block size for which the block routine 00033 * should be used; if the usable block size is less than 00034 * this value, an unblocked routine should be used. 00035 * = 3: the crossover point (in a block routine, for N less 00036 * than this value, an unblocked routine should be used) 00037 * = 4: the number of shifts, used in the nonsymmetric 00038 * eigenvalue routines 00039 * = 5: the minimum column dimension for blocking to be used; 00040 * rectangular blocks must have dimension at least k by m, 00041 * where k is given by ILAENV(2,...) and m by ILAENV(5,...) 00042 * = 6: the crossover point for the SVD (when reducing an m by n 00043 * matrix to bidiagonal form, if max(m,n)/min(m,n) exceeds 00044 * this value, a QR factorization is used first to reduce 00045 * the matrix to a triangular form.) 00046 * = 7: the number of processors 00047 * = 8: the crossover point for the multishift QR and QZ methods 00048 * for nonsymmetric eigenvalue problems. 00049 * = 9: maximum size of the subproblems at the bottom of the 00050 * computation tree in the divide-and-conquer algorithm 00051 * =10: ieee NaN arithmetic can be trusted not to trap 00052 * =11: infinity arithmetic can be trusted not to trap 00053 * 12 <= ISPEC <= 16: 00054 * xHSEQR or one of its subroutines, 00055 * see IPARMQ for detailed explanation 00056 * 00057 * Other specifications (up to 100) can be added later. 00058 * 00059 * NAME (input) CHARACTER*(*) 00060 * The name of the calling subroutine. 00061 * 00062 * OPTS (input) CHARACTER*(*) 00063 * The character options to the subroutine NAME, concatenated 00064 * into a single character string. For example, UPLO = 'U', 00065 * TRANS = 'T', and DIAG = 'N' for a triangular routine would 00066 * be specified as OPTS = 'UTN'. 00067 * 00068 * N1 (input) INTEGER 00069 * N2 (input) INTEGER 00070 * N3 (input) INTEGER 00071 * N4 (input) INTEGER 00072 * Problem dimensions for the subroutine NAME; these may not all 00073 * be required. 00074 * 00075 * (ILAENV) (output) INTEGER 00076 * >= 0: the value of the parameter specified by ISPEC 00077 * < 0: if ILAENV = -k, the k-th argument had an illegal value. 00078 * 00079 * Further Details 00080 * =============== 00081 * 00082 * The following conventions have been used when calling ILAENV from the 00083 * LAPACK routines: 00084 * 1) OPTS is a concatenation of all of the character options to 00085 * subroutine NAME, in the same order that they appear in the 00086 * argument list for NAME, even if they are not used in determining 00087 * the value of the parameter specified by ISPEC. 00088 * 2) The problem dimensions N1, N2, N3, N4 are specified in the order 00089 * that they appear in the argument list for NAME. N1 is used 00090 * first, N2 second, and so on, and unused problem dimensions are 00091 * passed a value of -1. 00092 * 3) The parameter value returned by ILAENV is checked for validity in 00093 * the calling subroutine. For example, ILAENV is used to retrieve 00094 * the optimal blocksize for STRTRI as follows: 00095 * 00096 * NB = ILAENV( 1, 'STRTRI', UPLO // DIAG, N, -1, -1, -1 ) 00097 * IF( NB.LE.1 ) NB = MAX( 1, N ) 00098 * 00099 * ===================================================================== 00100 * 00101 * .. Intrinsic Functions .. 00102 INTRINSIC INT, MIN, REAL 00103 * .. 00104 * .. External Functions .. 00105 INTEGER IEEECK 00106 EXTERNAL IEEECK 00107 * .. 00108 * .. Arrays in Common .. 00109 INTEGER IPARMS( 100 ) 00110 * .. 00111 * .. Common blocks .. 00112 COMMON / CLAENV / IPARMS 00113 * .. 00114 * .. Save statement .. 00115 SAVE / CLAENV / 00116 * .. 00117 * .. Executable Statements .. 00118 * 00119 IF( ISPEC.GE.1 .AND. ISPEC.LE.5 ) THEN 00120 * 00121 * Return a value from the common block. 00122 * 00123 ILAENV = IPARMS( ISPEC ) 00124 * 00125 ELSE IF( ISPEC.EQ.6 ) THEN 00126 * 00127 * Compute SVD crossover point. 00128 * 00129 ILAENV = INT( REAL( MIN( N1, N2 ) )*1.6E0 ) 00130 * 00131 ELSE IF( ISPEC.GE.7 .AND. ISPEC.LE.9 ) THEN 00132 * 00133 * Return a value from the common block. 00134 * 00135 ILAENV = IPARMS( ISPEC ) 00136 * 00137 ELSE IF( ISPEC.EQ.10 ) THEN 00138 * 00139 * IEEE NaN arithmetic can be trusted not to trap 00140 * 00141 C ILAENV = 0 00142 ILAENV = 1 00143 IF( ILAENV.EQ.1 ) THEN 00144 ILAENV = IEEECK( 1, 0.0, 1.0 ) 00145 END IF 00146 * 00147 ELSE IF( ISPEC.EQ.11 ) THEN 00148 * 00149 * Infinity arithmetic can be trusted not to trap 00150 * 00151 C ILAENV = 0 00152 ILAENV = 1 00153 IF( ILAENV.EQ.1 ) THEN 00154 ILAENV = IEEECK( 0, 0.0, 1.0 ) 00155 END IF 00156 * 00157 ELSE IF(( ISPEC.GE.12 ) .AND. (ISPEC.LE.16)) THEN 00158 * 00159 * 12 <= ISPEC <= 16: xHSEQR or one of its subroutines. 00160 * 00161 ILAENV = IPARMS( ISPEC ) 00162 * WRITE(*,*) 'ISPEC = ',ISPEC,' ILAENV =',ILAENV 00163 * ILAENV = IPARMQ( ISPEC, NAME, OPTS, N1, N2, N3, N4 ) 00164 * 00165 ELSE 00166 * 00167 * Invalid value for ISPEC 00168 * 00169 ILAENV = -1 00170 END IF 00171 * 00172 RETURN 00173 * 00174 * End of ILAENV 00175 * 00176 END 00177 INTEGER FUNCTION IPARMQ( ISPEC, NAME, OPTS, N, ILO, IHI, LWORK ) 00178 * 00179 INTEGER INMIN, INWIN, INIBL, ISHFTS, IACC22 00180 PARAMETER ( INMIN = 12, INWIN = 13, INIBL = 14, 00181 $ ISHFTS = 15, IACC22 = 16 ) 00182 INTEGER NMIN, K22MIN, KACMIN, NIBBLE, KNWSWP 00183 PARAMETER ( NMIN = 11, K22MIN = 14, KACMIN = 14, 00184 $ NIBBLE = 14, KNWSWP = 500 ) 00185 REAL TWO 00186 PARAMETER ( TWO = 2.0 ) 00187 * .. 00188 * .. Scalar Arguments .. 00189 INTEGER IHI, ILO, ISPEC, LWORK, N 00190 CHARACTER NAME*( * ), OPTS*( * ) 00191 * .. 00192 * .. Local Scalars .. 00193 INTEGER NH, NS 00194 * .. 00195 * .. Intrinsic Functions .. 00196 INTRINSIC LOG, MAX, MOD, NINT, REAL 00197 * .. 00198 * .. Executable Statements .. 00199 IF( ( ISPEC.EQ.ISHFTS ) .OR. ( ISPEC.EQ.INWIN ) .OR. 00200 $ ( ISPEC.EQ.IACC22 ) ) THEN 00201 * 00202 * ==== Set the number simultaneous shifts ==== 00203 * 00204 NH = IHI - ILO + 1 00205 NS = 2 00206 IF( NH.GE.30 ) 00207 $ NS = 4 00208 IF( NH.GE.60 ) 00209 $ NS = 10 00210 IF( NH.GE.150 ) 00211 $ NS = MAX( 10, NH / NINT( LOG( REAL( NH ) ) / LOG( TWO ) ) ) 00212 IF( NH.GE.590 ) 00213 $ NS = 64 00214 IF( NH.GE.3000 ) 00215 $ NS = 128 00216 IF( NH.GE.6000 ) 00217 $ NS = 256 00218 NS = MAX( 2, NS-MOD( NS, 2 ) ) 00219 END IF 00220 * 00221 IF( ISPEC.EQ.INMIN ) THEN 00222 * 00223 * 00224 * ===== Matrices of order smaller than NMIN get sent 00225 * . to LAHQR, the classic double shift algorithm. 00226 * . This must be at least 11. ==== 00227 * 00228 IPARMQ = NMIN 00229 * 00230 ELSE IF( ISPEC.EQ.INIBL ) THEN 00231 * 00232 * ==== INIBL: skip a multi-shift qr iteration and 00233 * . whenever aggressive early deflation finds 00234 * . at least (NIBBLE*(window size)/100) deflations. ==== 00235 * 00236 IPARMQ = NIBBLE 00237 * 00238 ELSE IF( ISPEC.EQ.ISHFTS ) THEN 00239 * 00240 * ==== NSHFTS: The number of simultaneous shifts ===== 00241 * 00242 IPARMQ = NS 00243 * 00244 ELSE IF( ISPEC.EQ.INWIN ) THEN 00245 * 00246 * ==== NW: deflation window size. ==== 00247 * 00248 IF( NH.LE.KNWSWP ) THEN 00249 IPARMQ = NS 00250 ELSE 00251 IPARMQ = 3*NS / 2 00252 END IF 00253 * 00254 ELSE IF( ISPEC.EQ.IACC22 ) THEN 00255 * 00256 * ==== IACC22: Whether to accumulate reflections 00257 * . before updating the far-from-diagonal elements 00258 * . and whether to use 2-by-2 block structure while 00259 * . doing it. A small amount of work could be saved 00260 * . by making this choice dependent also upon the 00261 * . NH=IHI-ILO+1. 00262 * 00263 IPARMQ = 0 00264 IF( NS.GE.KACMIN ) 00265 $ IPARMQ = 1 00266 IF( NS.GE.K22MIN ) 00267 $ IPARMQ = 2 00268 * 00269 ELSE 00270 * ===== invalid value of ispec ===== 00271 IPARMQ = -1 00272 * 00273 END IF 00274 * 00275 * ==== End of IPARMQ ==== 00276 * 00277 END
1.7.3 
