org.netlib.lapack
Class Slaln2

java.lang.Object
  extended by org.netlib.lapack.Slaln2

public class Slaln2
extends java.lang.Object

Following is the description from the original
Fortran source.  For each array argument, the Java
version will include an integer offset parameter, so
the arguments may not match the description exactly.
Contact seymour@cs.utk.edu with any questions.

* .. * * Purpose * ======= * * SLALN2 solves a system of the form (ca A - w D ) X = s B * or (ca A' - w D) X = s B with possible scaling ("s") and * perturbation of A. (A' means A-transpose.) * * A is an NA x NA real matrix, ca is a real scalar, D is an NA x NA * real diagonal matrix, w is a real or complex value, and X and B are * NA x 1 matrices -- real if w is real, complex if w is complex. NA * may be 1 or 2. * * If w is complex, X and B are represented as NA x 2 matrices, * the first column of each being the real part and the second * being the imaginary part. * * "s" is a scaling factor (.LE. 1), computed by SLALN2, which is * so chosen that X can be computed without overflow. X is further * scaled if necessary to assure that norm(ca A - w D)*norm(X) is less * than overflow. * * If both singular values of (ca A - w D) are less than SMIN, * SMIN*identity will be used instead of (ca A - w D). If only one * singular value is less than SMIN, one element of (ca A - w D) will be * perturbed enough to make the smallest singular value roughly SMIN. * If both singular values are at least SMIN, (ca A - w D) will not be * perturbed. In any case, the perturbation will be at most some small * multiple of max( SMIN, ulp*norm(ca A - w D) ). The singular values * are computed by infinity-norm approximations, and thus will only be * correct to a factor of 2 or so. * * Note: all input quantities are assumed to be smaller than overflow * by a reasonable factor. (See BIGNUM.) * * Arguments * ========== * * LTRANS (input) LOGICAL * =.TRUE.: A-transpose will be used. * =.FALSE.: A will be used (not transposed.) * * NA (input) INTEGER * The size of the matrix A. It may (only) be 1 or 2. * * NW (input) INTEGER * 1 if "w" is real, 2 if "w" is complex. It may only be 1 * or 2. * * SMIN (input) REAL * The desired lower bound on the singular values of A. This * should be a safe distance away from underflow or overflow, * say, between (underflow/machine precision) and (machine * precision * overflow ). (See BIGNUM and ULP.) * * CA (input) REAL * The coefficient c, which A is multiplied by. * * A (input) REAL array, dimension (LDA,NA) * The NA x NA matrix A. * * LDA (input) INTEGER * The leading dimension of A. It must be at least NA. * * D1 (input) REAL * The 1,1 element in the diagonal matrix D. * * D2 (input) REAL * The 2,2 element in the diagonal matrix D. Not used if NW=1. * * B (input) REAL array, dimension (LDB,NW) * The NA x NW matrix B (right-hand side). If NW=2 ("w" is * complex), column 1 contains the real part of B and column 2 * contains the imaginary part. * * LDB (input) INTEGER * The leading dimension of B. It must be at least NA. * * WR (input) REAL * The real part of the scalar "w". * * WI (input) REAL * The imaginary part of the scalar "w". Not used if NW=1. * * X (output) REAL array, dimension (LDX,NW) * The NA x NW matrix X (unknowns), as computed by SLALN2. * If NW=2 ("w" is complex), on exit, column 1 will contain * the real part of X and column 2 will contain the imaginary * part. * * LDX (input) INTEGER * The leading dimension of X. It must be at least NA. * * SCALE (output) REAL * The scale factor that B must be multiplied by to insure * that overflow does not occur when computing X. Thus, * (ca A - w D) X will be SCALE*B, not B (ignoring * perturbations of A.) It will be at most 1. * * XNORM (output) REAL * The infinity-norm of X, when X is regarded as an NA x NW * real matrix. * * INFO (output) INTEGER * An error flag. It will be set to zero if no error occurs, * a negative number if an argument is in error, or a positive * number if ca A - w D had to be perturbed. * The possible values are: * = 0: No error occurred, and (ca A - w D) did not have to be * perturbed. * = 1: (ca A - w D) had to be perturbed to make its smallest * (or only) singular value greater than SMIN. * NOTE: In the interests of speed, this routine does not * check the inputs for errors. * * ===================================================================== * * .. Parameters ..


Field Summary
static float[] ci_civ
           
static float[] cr_crv
           
static boolean[] cswap
           
static int[] ipivot
           
static boolean[] rswap
           
 
Constructor Summary
Slaln2()
           
 
Method Summary
static void slaln2(boolean ltrans, int na, int nw, float smin, float ca, float[] a, int _a_offset, int lda, float d1, float d2, float[] b, int _b_offset, int ldb, float wr, float wi, float[] x, int _x_offset, int ldx, floatW scale, floatW xnorm, intW info)
           
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

ci_civ

public static float[] ci_civ

cr_crv

public static float[] cr_crv

cswap

public static boolean[] cswap

rswap

public static boolean[] rswap

ipivot

public static int[] ipivot
Constructor Detail

Slaln2

public Slaln2()
Method Detail

slaln2

public static void slaln2(boolean ltrans,
                          int na,
                          int nw,
                          float smin,
                          float ca,
                          float[] a,
                          int _a_offset,
                          int lda,
                          float d1,
                          float d2,
                          float[] b,
                          int _b_offset,
                          int ldb,
                          float wr,
                          float wi,
                          float[] x,
                          int _x_offset,
                          int ldx,
                          floatW scale,
                          floatW xnorm,
                          intW info)