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LAPACK
3.4.1
LAPACK: Linear Algebra PACKage
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00001 *> \brief \b SSPTRF 00002 * 00003 * =========== DOCUMENTATION =========== 00004 * 00005 * Online html documentation available at 00006 * http://www.netlib.org/lapack/explore-html/ 00007 * 00008 *> \htmlonly 00009 *> Download SSPTRF + dependencies 00010 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/ssptrf.f"> 00011 *> [TGZ]</a> 00012 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/ssptrf.f"> 00013 *> [ZIP]</a> 00014 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/ssptrf.f"> 00015 *> [TXT]</a> 00016 *> \endhtmlonly 00017 * 00018 * Definition: 00019 * =========== 00020 * 00021 * SUBROUTINE SSPTRF( UPLO, N, AP, IPIV, INFO ) 00022 * 00023 * .. Scalar Arguments .. 00024 * CHARACTER UPLO 00025 * INTEGER INFO, N 00026 * .. 00027 * .. Array Arguments .. 00028 * INTEGER IPIV( * ) 00029 * REAL AP( * ) 00030 * .. 00031 * 00032 * 00033 *> \par Purpose: 00034 * ============= 00035 *> 00036 *> \verbatim 00037 *> 00038 *> SSPTRF computes the factorization of a real symmetric matrix A stored 00039 *> in packed format using the Bunch-Kaufman diagonal pivoting method: 00040 *> 00041 *> A = U*D*U**T or A = L*D*L**T 00042 *> 00043 *> where U (or L) is a product of permutation and unit upper (lower) 00044 *> triangular matrices, and D is symmetric and block diagonal with 00045 *> 1-by-1 and 2-by-2 diagonal blocks. 00046 *> \endverbatim 00047 * 00048 * Arguments: 00049 * ========== 00050 * 00051 *> \param[in] UPLO 00052 *> \verbatim 00053 *> UPLO is CHARACTER*1 00054 *> = 'U': Upper triangle of A is stored; 00055 *> = 'L': Lower triangle of A is stored. 00056 *> \endverbatim 00057 *> 00058 *> \param[in] N 00059 *> \verbatim 00060 *> N is INTEGER 00061 *> The order of the matrix A. N >= 0. 00062 *> \endverbatim 00063 *> 00064 *> \param[in,out] AP 00065 *> \verbatim 00066 *> AP is REAL array, dimension (N*(N+1)/2) 00067 *> On entry, the upper or lower triangle of the symmetric matrix 00068 *> A, packed columnwise in a linear array. The j-th column of A 00069 *> is stored in the array AP as follows: 00070 *> if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; 00071 *> if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n. 00072 *> 00073 *> On exit, the block diagonal matrix D and the multipliers used 00074 *> to obtain the factor U or L, stored as a packed triangular 00075 *> matrix overwriting A (see below for further details). 00076 *> \endverbatim 00077 *> 00078 *> \param[out] IPIV 00079 *> \verbatim 00080 *> IPIV is INTEGER array, dimension (N) 00081 *> Details of the interchanges and the block structure of D. 00082 *> If IPIV(k) > 0, then rows and columns k and IPIV(k) were 00083 *> interchanged and D(k,k) is a 1-by-1 diagonal block. 00084 *> If UPLO = 'U' and IPIV(k) = IPIV(k-1) < 0, then rows and 00085 *> columns k-1 and -IPIV(k) were interchanged and D(k-1:k,k-1:k) 00086 *> is a 2-by-2 diagonal block. If UPLO = 'L' and IPIV(k) = 00087 *> IPIV(k+1) < 0, then rows and columns k+1 and -IPIV(k) were 00088 *> interchanged and D(k:k+1,k:k+1) is a 2-by-2 diagonal block. 00089 *> \endverbatim 00090 *> 00091 *> \param[out] INFO 00092 *> \verbatim 00093 *> INFO is INTEGER 00094 *> = 0: successful exit 00095 *> < 0: if INFO = -i, the i-th argument had an illegal value 00096 *> > 0: if INFO = i, D(i,i) is exactly zero. The factorization 00097 *> has been completed, but the block diagonal matrix D is 00098 *> exactly singular, and division by zero will occur if it 00099 *> is used to solve a system of equations. 00100 *> \endverbatim 00101 * 00102 * Authors: 00103 * ======== 00104 * 00105 *> \author Univ. of Tennessee 00106 *> \author Univ. of California Berkeley 00107 *> \author Univ. of Colorado Denver 00108 *> \author NAG Ltd. 00109 * 00110 *> \date November 2011 00111 * 00112 *> \ingroup realOTHERcomputational 00113 * 00114 *> \par Further Details: 00115 * ===================== 00116 *> 00117 *> \verbatim 00118 *> 00119 *> 5-96 - Based on modifications by J. Lewis, Boeing Computer Services 00120 *> Company 00121 *> 00122 *> If UPLO = 'U', then A = U*D*U**T, where 00123 *> U = P(n)*U(n)* ... *P(k)U(k)* ..., 00124 *> i.e., U is a product of terms P(k)*U(k), where k decreases from n to 00125 *> 1 in steps of 1 or 2, and D is a block diagonal matrix with 1-by-1 00126 *> and 2-by-2 diagonal blocks D(k). P(k) is a permutation matrix as 00127 *> defined by IPIV(k), and U(k) is a unit upper triangular matrix, such 00128 *> that if the diagonal block D(k) is of order s (s = 1 or 2), then 00129 *> 00130 *> ( I v 0 ) k-s 00131 *> U(k) = ( 0 I 0 ) s 00132 *> ( 0 0 I ) n-k 00133 *> k-s s n-k 00134 *> 00135 *> If s = 1, D(k) overwrites A(k,k), and v overwrites A(1:k-1,k). 00136 *> If s = 2, the upper triangle of D(k) overwrites A(k-1,k-1), A(k-1,k), 00137 *> and A(k,k), and v overwrites A(1:k-2,k-1:k). 00138 *> 00139 *> If UPLO = 'L', then A = L*D*L**T, where 00140 *> L = P(1)*L(1)* ... *P(k)*L(k)* ..., 00141 *> i.e., L is a product of terms P(k)*L(k), where k increases from 1 to 00142 *> n in steps of 1 or 2, and D is a block diagonal matrix with 1-by-1 00143 *> and 2-by-2 diagonal blocks D(k). P(k) is a permutation matrix as 00144 *> defined by IPIV(k), and L(k) is a unit lower triangular matrix, such 00145 *> that if the diagonal block D(k) is of order s (s = 1 or 2), then 00146 *> 00147 *> ( I 0 0 ) k-1 00148 *> L(k) = ( 0 I 0 ) s 00149 *> ( 0 v I ) n-k-s+1 00150 *> k-1 s n-k-s+1 00151 *> 00152 *> If s = 1, D(k) overwrites A(k,k), and v overwrites A(k+1:n,k). 00153 *> If s = 2, the lower triangle of D(k) overwrites A(k,k), A(k+1,k), 00154 *> and A(k+1,k+1), and v overwrites A(k+2:n,k:k+1). 00155 *> \endverbatim 00156 *> 00157 * ===================================================================== 00158 SUBROUTINE SSPTRF( UPLO, N, AP, IPIV, INFO ) 00159 * 00160 * -- LAPACK computational routine (version 3.4.0) -- 00161 * -- LAPACK is a software package provided by Univ. of Tennessee, -- 00162 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- 00163 * November 2011 00164 * 00165 * .. Scalar Arguments .. 00166 CHARACTER UPLO 00167 INTEGER INFO, N 00168 * .. 00169 * .. Array Arguments .. 00170 INTEGER IPIV( * ) 00171 REAL AP( * ) 00172 * .. 00173 * 00174 * ===================================================================== 00175 * 00176 * .. Parameters .. 00177 REAL ZERO, ONE 00178 PARAMETER ( ZERO = 0.0E+0, ONE = 1.0E+0 ) 00179 REAL EIGHT, SEVTEN 00180 PARAMETER ( EIGHT = 8.0E+0, SEVTEN = 17.0E+0 ) 00181 * .. 00182 * .. Local Scalars .. 00183 LOGICAL UPPER 00184 INTEGER I, IMAX, J, JMAX, K, KC, KK, KNC, KP, KPC, 00185 $ KSTEP, KX, NPP 00186 REAL ABSAKK, ALPHA, COLMAX, D11, D12, D21, D22, R1, 00187 $ ROWMAX, T, WK, WKM1, WKP1 00188 * .. 00189 * .. External Functions .. 00190 LOGICAL LSAME 00191 INTEGER ISAMAX 00192 EXTERNAL LSAME, ISAMAX 00193 * .. 00194 * .. External Subroutines .. 00195 EXTERNAL SSCAL, SSPR, SSWAP, XERBLA 00196 * .. 00197 * .. Intrinsic Functions .. 00198 INTRINSIC ABS, MAX, SQRT 00199 * .. 00200 * .. Executable Statements .. 00201 * 00202 * Test the input parameters. 00203 * 00204 INFO = 0 00205 UPPER = LSAME( UPLO, 'U' ) 00206 IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN 00207 INFO = -1 00208 ELSE IF( N.LT.0 ) THEN 00209 INFO = -2 00210 END IF 00211 IF( INFO.NE.0 ) THEN 00212 CALL XERBLA( 'SSPTRF', -INFO ) 00213 RETURN 00214 END IF 00215 * 00216 * Initialize ALPHA for use in choosing pivot block size. 00217 * 00218 ALPHA = ( ONE+SQRT( SEVTEN ) ) / EIGHT 00219 * 00220 IF( UPPER ) THEN 00221 * 00222 * Factorize A as U*D*U**T using the upper triangle of A 00223 * 00224 * K is the main loop index, decreasing from N to 1 in steps of 00225 * 1 or 2 00226 * 00227 K = N 00228 KC = ( N-1 )*N / 2 + 1 00229 10 CONTINUE 00230 KNC = KC 00231 * 00232 * If K < 1, exit from loop 00233 * 00234 IF( K.LT.1 ) 00235 $ GO TO 110 00236 KSTEP = 1 00237 * 00238 * Determine rows and columns to be interchanged and whether 00239 * a 1-by-1 or 2-by-2 pivot block will be used 00240 * 00241 ABSAKK = ABS( AP( KC+K-1 ) ) 00242 * 00243 * IMAX is the row-index of the largest off-diagonal element in 00244 * column K, and COLMAX is its absolute value 00245 * 00246 IF( K.GT.1 ) THEN 00247 IMAX = ISAMAX( K-1, AP( KC ), 1 ) 00248 COLMAX = ABS( AP( KC+IMAX-1 ) ) 00249 ELSE 00250 COLMAX = ZERO 00251 END IF 00252 * 00253 IF( MAX( ABSAKK, COLMAX ).EQ.ZERO ) THEN 00254 * 00255 * Column K is zero: set INFO and continue 00256 * 00257 IF( INFO.EQ.0 ) 00258 $ INFO = K 00259 KP = K 00260 ELSE 00261 IF( ABSAKK.GE.ALPHA*COLMAX ) THEN 00262 * 00263 * no interchange, use 1-by-1 pivot block 00264 * 00265 KP = K 00266 ELSE 00267 * 00268 ROWMAX = ZERO 00269 JMAX = IMAX 00270 KX = IMAX*( IMAX+1 ) / 2 + IMAX 00271 DO 20 J = IMAX + 1, K 00272 IF( ABS( AP( KX ) ).GT.ROWMAX ) THEN 00273 ROWMAX = ABS( AP( KX ) ) 00274 JMAX = J 00275 END IF 00276 KX = KX + J 00277 20 CONTINUE 00278 KPC = ( IMAX-1 )*IMAX / 2 + 1 00279 IF( IMAX.GT.1 ) THEN 00280 JMAX = ISAMAX( IMAX-1, AP( KPC ), 1 ) 00281 ROWMAX = MAX( ROWMAX, ABS( AP( KPC+JMAX-1 ) ) ) 00282 END IF 00283 * 00284 IF( ABSAKK.GE.ALPHA*COLMAX*( COLMAX / ROWMAX ) ) THEN 00285 * 00286 * no interchange, use 1-by-1 pivot block 00287 * 00288 KP = K 00289 ELSE IF( ABS( AP( KPC+IMAX-1 ) ).GE.ALPHA*ROWMAX ) THEN 00290 * 00291 * interchange rows and columns K and IMAX, use 1-by-1 00292 * pivot block 00293 * 00294 KP = IMAX 00295 ELSE 00296 * 00297 * interchange rows and columns K-1 and IMAX, use 2-by-2 00298 * pivot block 00299 * 00300 KP = IMAX 00301 KSTEP = 2 00302 END IF 00303 END IF 00304 * 00305 KK = K - KSTEP + 1 00306 IF( KSTEP.EQ.2 ) 00307 $ KNC = KNC - K + 1 00308 IF( KP.NE.KK ) THEN 00309 * 00310 * Interchange rows and columns KK and KP in the leading 00311 * submatrix A(1:k,1:k) 00312 * 00313 CALL SSWAP( KP-1, AP( KNC ), 1, AP( KPC ), 1 ) 00314 KX = KPC + KP - 1 00315 DO 30 J = KP + 1, KK - 1 00316 KX = KX + J - 1 00317 T = AP( KNC+J-1 ) 00318 AP( KNC+J-1 ) = AP( KX ) 00319 AP( KX ) = T 00320 30 CONTINUE 00321 T = AP( KNC+KK-1 ) 00322 AP( KNC+KK-1 ) = AP( KPC+KP-1 ) 00323 AP( KPC+KP-1 ) = T 00324 IF( KSTEP.EQ.2 ) THEN 00325 T = AP( KC+K-2 ) 00326 AP( KC+K-2 ) = AP( KC+KP-1 ) 00327 AP( KC+KP-1 ) = T 00328 END IF 00329 END IF 00330 * 00331 * Update the leading submatrix 00332 * 00333 IF( KSTEP.EQ.1 ) THEN 00334 * 00335 * 1-by-1 pivot block D(k): column k now holds 00336 * 00337 * W(k) = U(k)*D(k) 00338 * 00339 * where U(k) is the k-th column of U 00340 * 00341 * Perform a rank-1 update of A(1:k-1,1:k-1) as 00342 * 00343 * A := A - U(k)*D(k)*U(k)**T = A - W(k)*1/D(k)*W(k)**T 00344 * 00345 R1 = ONE / AP( KC+K-1 ) 00346 CALL SSPR( UPLO, K-1, -R1, AP( KC ), 1, AP ) 00347 * 00348 * Store U(k) in column k 00349 * 00350 CALL SSCAL( K-1, R1, AP( KC ), 1 ) 00351 ELSE 00352 * 00353 * 2-by-2 pivot block D(k): columns k and k-1 now hold 00354 * 00355 * ( W(k-1) W(k) ) = ( U(k-1) U(k) )*D(k) 00356 * 00357 * where U(k) and U(k-1) are the k-th and (k-1)-th columns 00358 * of U 00359 * 00360 * Perform a rank-2 update of A(1:k-2,1:k-2) as 00361 * 00362 * A := A - ( U(k-1) U(k) )*D(k)*( U(k-1) U(k) )**T 00363 * = A - ( W(k-1) W(k) )*inv(D(k))*( W(k-1) W(k) )**T 00364 * 00365 IF( K.GT.2 ) THEN 00366 * 00367 D12 = AP( K-1+( K-1 )*K / 2 ) 00368 D22 = AP( K-1+( K-2 )*( K-1 ) / 2 ) / D12 00369 D11 = AP( K+( K-1 )*K / 2 ) / D12 00370 T = ONE / ( D11*D22-ONE ) 00371 D12 = T / D12 00372 * 00373 DO 50 J = K - 2, 1, -1 00374 WKM1 = D12*( D11*AP( J+( K-2 )*( K-1 ) / 2 )- 00375 $ AP( J+( K-1 )*K / 2 ) ) 00376 WK = D12*( D22*AP( J+( K-1 )*K / 2 )- 00377 $ AP( J+( K-2 )*( K-1 ) / 2 ) ) 00378 DO 40 I = J, 1, -1 00379 AP( I+( J-1 )*J / 2 ) = AP( I+( J-1 )*J / 2 ) - 00380 $ AP( I+( K-1 )*K / 2 )*WK - 00381 $ AP( I+( K-2 )*( K-1 ) / 2 )*WKM1 00382 40 CONTINUE 00383 AP( J+( K-1 )*K / 2 ) = WK 00384 AP( J+( K-2 )*( K-1 ) / 2 ) = WKM1 00385 50 CONTINUE 00386 * 00387 END IF 00388 * 00389 END IF 00390 END IF 00391 * 00392 * Store details of the interchanges in IPIV 00393 * 00394 IF( KSTEP.EQ.1 ) THEN 00395 IPIV( K ) = KP 00396 ELSE 00397 IPIV( K ) = -KP 00398 IPIV( K-1 ) = -KP 00399 END IF 00400 * 00401 * Decrease K and return to the start of the main loop 00402 * 00403 K = K - KSTEP 00404 KC = KNC - K 00405 GO TO 10 00406 * 00407 ELSE 00408 * 00409 * Factorize A as L*D*L**T using the lower triangle of A 00410 * 00411 * K is the main loop index, increasing from 1 to N in steps of 00412 * 1 or 2 00413 * 00414 K = 1 00415 KC = 1 00416 NPP = N*( N+1 ) / 2 00417 60 CONTINUE 00418 KNC = KC 00419 * 00420 * If K > N, exit from loop 00421 * 00422 IF( K.GT.N ) 00423 $ GO TO 110 00424 KSTEP = 1 00425 * 00426 * Determine rows and columns to be interchanged and whether 00427 * a 1-by-1 or 2-by-2 pivot block will be used 00428 * 00429 ABSAKK = ABS( AP( KC ) ) 00430 * 00431 * IMAX is the row-index of the largest off-diagonal element in 00432 * column K, and COLMAX is its absolute value 00433 * 00434 IF( K.LT.N ) THEN 00435 IMAX = K + ISAMAX( N-K, AP( KC+1 ), 1 ) 00436 COLMAX = ABS( AP( KC+IMAX-K ) ) 00437 ELSE 00438 COLMAX = ZERO 00439 END IF 00440 * 00441 IF( MAX( ABSAKK, COLMAX ).EQ.ZERO ) THEN 00442 * 00443 * Column K is zero: set INFO and continue 00444 * 00445 IF( INFO.EQ.0 ) 00446 $ INFO = K 00447 KP = K 00448 ELSE 00449 IF( ABSAKK.GE.ALPHA*COLMAX ) THEN 00450 * 00451 * no interchange, use 1-by-1 pivot block 00452 * 00453 KP = K 00454 ELSE 00455 * 00456 * JMAX is the column-index of the largest off-diagonal 00457 * element in row IMAX, and ROWMAX is its absolute value 00458 * 00459 ROWMAX = ZERO 00460 KX = KC + IMAX - K 00461 DO 70 J = K, IMAX - 1 00462 IF( ABS( AP( KX ) ).GT.ROWMAX ) THEN 00463 ROWMAX = ABS( AP( KX ) ) 00464 JMAX = J 00465 END IF 00466 KX = KX + N - J 00467 70 CONTINUE 00468 KPC = NPP - ( N-IMAX+1 )*( N-IMAX+2 ) / 2 + 1 00469 IF( IMAX.LT.N ) THEN 00470 JMAX = IMAX + ISAMAX( N-IMAX, AP( KPC+1 ), 1 ) 00471 ROWMAX = MAX( ROWMAX, ABS( AP( KPC+JMAX-IMAX ) ) ) 00472 END IF 00473 * 00474 IF( ABSAKK.GE.ALPHA*COLMAX*( COLMAX / ROWMAX ) ) THEN 00475 * 00476 * no interchange, use 1-by-1 pivot block 00477 * 00478 KP = K 00479 ELSE IF( ABS( AP( KPC ) ).GE.ALPHA*ROWMAX ) THEN 00480 * 00481 * interchange rows and columns K and IMAX, use 1-by-1 00482 * pivot block 00483 * 00484 KP = IMAX 00485 ELSE 00486 * 00487 * interchange rows and columns K+1 and IMAX, use 2-by-2 00488 * pivot block 00489 * 00490 KP = IMAX 00491 KSTEP = 2 00492 END IF 00493 END IF 00494 * 00495 KK = K + KSTEP - 1 00496 IF( KSTEP.EQ.2 ) 00497 $ KNC = KNC + N - K + 1 00498 IF( KP.NE.KK ) THEN 00499 * 00500 * Interchange rows and columns KK and KP in the trailing 00501 * submatrix A(k:n,k:n) 00502 * 00503 IF( KP.LT.N ) 00504 $ CALL SSWAP( N-KP, AP( KNC+KP-KK+1 ), 1, AP( KPC+1 ), 00505 $ 1 ) 00506 KX = KNC + KP - KK 00507 DO 80 J = KK + 1, KP - 1 00508 KX = KX + N - J + 1 00509 T = AP( KNC+J-KK ) 00510 AP( KNC+J-KK ) = AP( KX ) 00511 AP( KX ) = T 00512 80 CONTINUE 00513 T = AP( KNC ) 00514 AP( KNC ) = AP( KPC ) 00515 AP( KPC ) = T 00516 IF( KSTEP.EQ.2 ) THEN 00517 T = AP( KC+1 ) 00518 AP( KC+1 ) = AP( KC+KP-K ) 00519 AP( KC+KP-K ) = T 00520 END IF 00521 END IF 00522 * 00523 * Update the trailing submatrix 00524 * 00525 IF( KSTEP.EQ.1 ) THEN 00526 * 00527 * 1-by-1 pivot block D(k): column k now holds 00528 * 00529 * W(k) = L(k)*D(k) 00530 * 00531 * where L(k) is the k-th column of L 00532 * 00533 IF( K.LT.N ) THEN 00534 * 00535 * Perform a rank-1 update of A(k+1:n,k+1:n) as 00536 * 00537 * A := A - L(k)*D(k)*L(k)**T = A - W(k)*(1/D(k))*W(k)**T 00538 * 00539 R1 = ONE / AP( KC ) 00540 CALL SSPR( UPLO, N-K, -R1, AP( KC+1 ), 1, 00541 $ AP( KC+N-K+1 ) ) 00542 * 00543 * Store L(k) in column K 00544 * 00545 CALL SSCAL( N-K, R1, AP( KC+1 ), 1 ) 00546 END IF 00547 ELSE 00548 * 00549 * 2-by-2 pivot block D(k): columns K and K+1 now hold 00550 * 00551 * ( W(k) W(k+1) ) = ( L(k) L(k+1) )*D(k) 00552 * 00553 * where L(k) and L(k+1) are the k-th and (k+1)-th columns 00554 * of L 00555 * 00556 IF( K.LT.N-1 ) THEN 00557 * 00558 * Perform a rank-2 update of A(k+2:n,k+2:n) as 00559 * 00560 * A := A - ( L(k) L(k+1) )*D(k)*( L(k) L(k+1) )**T 00561 * = A - ( W(k) W(k+1) )*inv(D(k))*( W(k) W(k+1) )**T 00562 * 00563 * where L(k) and L(k+1) are the k-th and (k+1)-th 00564 * columns of L 00565 * 00566 D21 = AP( K+1+( K-1 )*( 2*N-K ) / 2 ) 00567 D11 = AP( K+1+K*( 2*N-K-1 ) / 2 ) / D21 00568 D22 = AP( K+( K-1 )*( 2*N-K ) / 2 ) / D21 00569 T = ONE / ( D11*D22-ONE ) 00570 D21 = T / D21 00571 * 00572 DO 100 J = K + 2, N 00573 WK = D21*( D11*AP( J+( K-1 )*( 2*N-K ) / 2 )- 00574 $ AP( J+K*( 2*N-K-1 ) / 2 ) ) 00575 WKP1 = D21*( D22*AP( J+K*( 2*N-K-1 ) / 2 )- 00576 $ AP( J+( K-1 )*( 2*N-K ) / 2 ) ) 00577 * 00578 DO 90 I = J, N 00579 AP( I+( J-1 )*( 2*N-J ) / 2 ) = AP( I+( J-1 )* 00580 $ ( 2*N-J ) / 2 ) - AP( I+( K-1 )*( 2*N-K ) / 00581 $ 2 )*WK - AP( I+K*( 2*N-K-1 ) / 2 )*WKP1 00582 90 CONTINUE 00583 * 00584 AP( J+( K-1 )*( 2*N-K ) / 2 ) = WK 00585 AP( J+K*( 2*N-K-1 ) / 2 ) = WKP1 00586 * 00587 100 CONTINUE 00588 END IF 00589 END IF 00590 END IF 00591 * 00592 * Store details of the interchanges in IPIV 00593 * 00594 IF( KSTEP.EQ.1 ) THEN 00595 IPIV( K ) = KP 00596 ELSE 00597 IPIV( K ) = -KP 00598 IPIV( K+1 ) = -KP 00599 END IF 00600 * 00601 * Increase K and return to the start of the main loop 00602 * 00603 K = K + KSTEP 00604 KC = KNC + N - K + 2 00605 GO TO 60 00606 * 00607 END IF 00608 * 00609 110 CONTINUE 00610 RETURN 00611 * 00612 * End of SSPTRF 00613 * 00614 END