---
name: "sdrvev.f"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/sdrvev.f"
---

# sdrvev.f(3)

## NAME

TESTING/EIG/sdrvev.f

## SYNOPSIS

### Functions/Subroutines

subroutine **sdrvev** (nsizes, nn, ntypes, dotype, iseed, thresh, nounit, a, lda, h, wr, wi, wr1, wi1, vl, ldvl, vr, ldvr, lre, ldlre, result, work, nwork, iwork, info)\
 **SDRVEV**

## Function/Subroutine Documentation

### subroutine sdrvev (integer nsizes, integer, dimension( \* ) nn, integer ntypes, logical, dimension( \* ) dotype, integer, dimension( 4 ) iseed, real thresh, integer nounit, real, dimension( lda, \* ) a, integer lda, real, dimension( lda, \* ) h, real, dimension( \* ) wr, real, dimension( \* ) wi, real, dimension( \* ) wr1, real, dimension( \* ) wi1, real, dimension( ldvl, \* ) vl, integer ldvl, real, dimension( ldvr, \* ) vr, integer ldvr, real, dimension( ldlre, \* ) lre, integer ldlre, real, dimension( 7 ) result, real, dimension( \* ) work, integer nwork, integer, dimension( \* ) iwork, integer info)

**SDRVEV**

**Purpose:**

```
!>
!>    SDRVEV  checks the nonsymmetric eigenvalue problem driver SGEEV.
!>
!>    When SDRVEV is called, a number of matrix  () and a
!>    number of matrix  are specified.  For each size ()
!>    and each type of matrix, one matrix will be generated and used
!>    to test the nonsymmetric eigenroutines.  For each matrix, 7
!>    tests will be performed:
!>
!>    (1)     | A * VR - VR * W | / ( n |A| ulp )
!>
!>      Here VR is the matrix of unit right eigenvectors.
!>      W is a block diagonal matrix, with a 1x1 block for each
!>      real eigenvalue and a 2x2 block for each complex conjugate
!>      pair.  If eigenvalues j and j+1 are a complex conjugate pair,
!>      so WR(j) = WR(j+1) = wr and WI(j) = - WI(j+1) = wi, then the
!>      2 x 2 block corresponding to the pair will be:
!>
!>              (  wr  wi  )
!>              ( -wi  wr  )
!>
!>      Such a block multiplying an n x 2 matrix  ( ur ui ) on the
!>      right will be the same as multiplying  ur + i*ui  by  wr + i*wi.
!>
!>    (2)     | A**H * VL - VL * W**H | / ( n |A| ulp )
!>
!>      Here VL is the matrix of unit left eigenvectors, A**H is the
!>      conjugate transpose of A, and W is as above.
!>
!>    (3)     | |VR(i)| - 1 | / ulp and whether largest component real
!>
!>      VR(i) denotes the i-th column of VR.
!>
!>    (4)     | |VL(i)| - 1 | / ulp and whether largest component real
!>
!>      VL(i) denotes the i-th column of VL.
!>
!>    (5)     W(full) = W(partial)
!>
!>      W(full) denotes the eigenvalues computed when both VR and VL
!>      are also computed, and W(partial) denotes the eigenvalues
!>      computed when only W, only W and VR, or only W and VL are
!>      computed.
!>
!>    (6)     VR(full) = VR(partial)
!>
!>      VR(full) denotes the right eigenvectors computed when both VR
!>      and VL are computed, and VR(partial) denotes the result
!>      when only VR is computed.
!>
!>     (7)     VL(full) = VL(partial)
!>
!>      VL(full) denotes the left eigenvectors computed when both VR
!>      and VL are also computed, and VL(partial) denotes the result
!>      when only VL is computed.
!>
!>    The  are specified by an array NN(1:NSIZES); the value of
!>    each element NN(j) specifies one size.
!>    The  are specified by a logical array DOTYPE( 1:NTYPES );
!>    if DOTYPE(j) is .TRUE., then matrix type  will be generated.
!>    Currently, the list of possible types is:
!>
!>    (1)  The zero matrix.
!>    (2)  The identity matrix.
!>    (3)  A (transposed) Jordan block, with 1's on the diagonal.
!>
!>    (4)  A diagonal matrix with evenly spaced entries
!>         1, ..., ULP  and random signs.
!>         (ULP = (first number larger than 1) - 1 )
!>    (5)  A diagonal matrix with geometrically spaced entries
!>         1, ..., ULP  and random signs.
!>    (6)  A diagonal matrix with  entries 1, ULP, ..., ULP
!>         and random signs.
!>
!>    (7)  Same as (4), but multiplied by a constant near
!>         the overflow threshold
!>    (8)  Same as (4), but multiplied by a constant near
!>         the underflow threshold
!>
!>    (9)  A matrix of the form  U' T U, where U is orthogonal and
!>         T has evenly spaced entries 1, ..., ULP with random signs
!>         on the diagonal and random O(1) entries in the upper
!>         triangle.
!>
!>    (10) A matrix of the form  U' T U, where U is orthogonal and
!>         T has geometrically spaced entries 1, ..., ULP with random
!>         signs on the diagonal and random O(1) entries in the upper
!>         triangle.
!>
!>    (11) A matrix of the form  U' T U, where U is orthogonal and
!>         T has  entries 1, ULP,..., ULP with random
!>         signs on the diagonal and random O(1) entries in the upper
!>         triangle.
!>
!>    (12) A matrix of the form  U' T U, where U is orthogonal and
!>         T has real or complex conjugate paired eigenvalues randomly
!>         chosen from ( ULP, 1 ) and random O(1) entries in the upper
!>         triangle.
!>
!>    (13) A matrix of the form  X' T X, where X has condition
!>         SQRT( ULP ) and T has evenly spaced entries 1, ..., ULP
!>         with random signs on the diagonal and random O(1) entries
!>         in the upper triangle.
!>
!>    (14) A matrix of the form  X' T X, where X has condition
!>         SQRT( ULP ) and T has geometrically spaced entries
!>         1, ..., ULP with random signs on the diagonal and random
!>         O(1) entries in the upper triangle.
!>
!>    (15) A matrix of the form  X' T X, where X has condition
!>         SQRT( ULP ) and T has  entries 1, ULP,..., ULP
!>         with random signs on the diagonal and random O(1) entries
!>         in the upper triangle.
!>
!>    (16) A matrix of the form  X' T X, where X has condition
!>         SQRT( ULP ) and T has real or complex conjugate paired
!>         eigenvalues randomly chosen from ( ULP, 1 ) and random
!>         O(1) entries in the upper triangle.
!>
!>    (17) Same as (16), but multiplied by a constant
!>         near the overflow threshold
!>    (18) Same as (16), but multiplied by a constant
!>         near the underflow threshold
!>
!>    (19) Nonsymmetric matrix with random entries chosen from (-1,1).
!>         If N is at least 4, all entries in first two rows and last
!>         row, and first column and last two columns are zero.
!>    (20) Same as (19), but multiplied by a constant
!>         near the overflow threshold
!>    (21) Same as (19), but multiplied by a constant
!>         near the underflow threshold
!>
```

**Parameters**

*NSIZES*

```
!>          NSIZES is INTEGER
!>          The number of sizes of matrices to use.  If it is zero,
!>          SDRVEV does nothing.  It must be at least zero.
!>
```

*NN*

```
!>          NN is INTEGER array, dimension (NSIZES)
!>          An array containing the sizes to be used for the matrices.
!>          Zero values will be skipped.  The values must be at least
!>          zero.
!>
```

*NTYPES*

```
!>          NTYPES is INTEGER
!>          The number of elements in DOTYPE.   If it is zero, SDRVEV
!>          does nothing.  It must be at least zero.  If it is MAXTYP+1
!>          and NSIZES is 1, then an additional type, MAXTYP+1 is
!>          defined, which is to use whatever matrix is in A.  This
!>          is only useful if DOTYPE(1:MAXTYP) is .FALSE. and
!>          DOTYPE(MAXTYP+1) is .TRUE. .
!>
```

*DOTYPE*

```
!>          DOTYPE is LOGICAL array, dimension (NTYPES)
!>          If DOTYPE(j) is .TRUE., then for each size in NN a
!>          matrix of that size and of type j will be generated.
!>          If NTYPES is smaller than the maximum number of types
!>          defined (PARAMETER MAXTYP), then types NTYPES+1 through
!>          MAXTYP will not be generated.  If NTYPES is larger
!>          than MAXTYP, DOTYPE(MAXTYP+1) through DOTYPE(NTYPES)
!>          will be ignored.
!>
```

*ISEED*

```
!>          ISEED is INTEGER array, dimension (4)
!>          On entry ISEED specifies the seed of the random number
!>          generator. The array elements should be between 0 and 4095;
!>          if not they will be reduced mod 4096.  Also, ISEED(4) must
!>          be odd.  The random number generator uses a linear
!>          congruential sequence limited to small integers, and so
!>          should produce machine independent random numbers. The
!>          values of ISEED are changed on exit, and can be used in the
!>          next call to SDRVEV to continue the same random number
!>          sequence.
!>
```

*THRESH*

```
!>          THRESH is REAL
!>          A test will count as  if the , computed as
!>          described above, exceeds THRESH.  Note that the error
!>          is scaled to be O(1), so THRESH should be a reasonably
!>          small multiple of 1, e.g., 10 or 100.  In particular,
!>          it should not depend on the precision (single vs. double)
!>          or the size of the matrix.  It must be at least zero.
!>
```

*NOUNIT*

```
!>          NOUNIT is INTEGER
!>          The FORTRAN unit number for printing out error messages
!>          (e.g., if a routine returns INFO not equal to 0.)
!>
```

*A*

```
!>          A is REAL array, dimension (LDA, max(NN))
!>          Used to hold the matrix whose eigenvalues are to be
!>          computed.  On exit, A contains the last matrix actually used.
!>
```

*LDA*

```
!>          LDA is INTEGER
!>          The leading dimension of A, and H. LDA must be at
!>          least 1 and at least max(NN).
!>
```

*H*

```
!>          H is REAL array, dimension (LDA, max(NN))
!>          Another copy of the test matrix A, modified by SGEEV.
!>
```

*WR*

```
!>          WR is REAL array, dimension (max(NN))
!>
```

*WI*

```
!>          WI is REAL array, dimension (max(NN))
!>
!>          The real and imaginary parts of the eigenvalues of A.
!>          On exit, WR + WI*i are the eigenvalues of the matrix in A.
!>
```

*WR1*

```
!>          WR1 is REAL array, dimension (max(NN))
!>
```

*WI1*

```
!>          WI1 is REAL array, dimension (max(NN))
!>
!>          Like WR, WI, these arrays contain the eigenvalues of A,
!>          but those computed when SGEEV only computes a partial
!>          eigendecomposition, i.e. not the eigenvalues and left
!>          and right eigenvectors.
!>
```

*VL*

```
!>          VL is REAL array, dimension (LDVL, max(NN))
!>          VL holds the computed left eigenvectors.
!>
```

*LDVL*

```
!>          LDVL is INTEGER
!>          Leading dimension of VL. Must be at least max(1,max(NN)).
!>
```

*VR*

```
!>          VR is REAL array, dimension (LDVR, max(NN))
!>          VR holds the computed right eigenvectors.
!>
```

*LDVR*

```
!>          LDVR is INTEGER
!>          Leading dimension of VR. Must be at least max(1,max(NN)).
!>
```

*LRE*

```
!>          LRE is REAL array, dimension (LDLRE,max(NN))
!>          LRE holds the computed right or left eigenvectors.
!>
```

*LDLRE*

```
!>          LDLRE is INTEGER
!>          Leading dimension of LRE. Must be at least max(1,max(NN)).
!>
```

*RESULT*

```
!>          RESULT is REAL array, dimension (7)
!>          The values computed by the seven tests described above.
!>          The values are currently limited to 1/ulp, to avoid overflow.
!>
```

*WORK*

```
!>          WORK is REAL array, dimension (NWORK)
!>
```

*NWORK*

```
!>          NWORK is INTEGER
!>          The number of entries in WORK.  This must be at least
!>          5*NN(j)+2*NN(j)**2 for all j.
!>
```

*IWORK*

```
!>          IWORK is INTEGER array, dimension (max(NN))
!>
```

*INFO*

```
!>          INFO is INTEGER
!>          If 0, then everything ran OK.
!>           -1: NSIZES < 0
!>           -2: Some NN(j) < 0
!>           -3: NTYPES < 0
!>           -6: THRESH < 0
!>           -9: LDA < 1 or LDA < NMAX, where NMAX is max( NN(j) ).
!>          -16: LDVL < 1 or LDVL < NMAX, where NMAX is max( NN(j) ).
!>          -18: LDVR < 1 or LDVR < NMAX, where NMAX is max( NN(j) ).
!>          -20: LDLRE < 1 or LDLRE < NMAX, where NMAX is max( NN(j) ).
!>          -23: NWORK too small.
!>          If  SLATMR, SLATMS, SLATME or SGEEV returns an error code,
!>              the absolute value of it is returned.
!>
!>-----------------------------------------------------------------------
!>
!>     Some Local Variables and Parameters:
!>     ---- ----- --------- --- ----------
!>
!>     ZERO, ONE       Real 0 and 1.
!>     MAXTYP          The number of types defined.
!>     NMAX            Largest value in NN.
!>     NERRS           The number of tests which have exceeded THRESH
!>     COND, CONDS,
!>     IMODE           Values to be passed to the matrix generators.
!>     ANORM           Norm of A; passed to matrix generators.
!>
!>     OVFL, UNFL      Overflow and underflow thresholds.
!>     ULP, ULPINV     Finest relative precision and its inverse.
!>     RTULP, RTULPI   Square roots of the previous 4 values.
!>
!>             The following four arrays decode JTYPE:
!>     KTYPE(j)        The general type (1-10) for type .
!>     KMODE(j)        The MODE value to be passed to the matrix
!>                     generator for type .
!>     KMAGN(j)        The order of magnitude ( O(1),
!>                     O(overflow^(1/2) ), O(underflow^(1/2) )
!>     KCONDS(j)       Selectw whether CONDS is to be 1 or
!>                     1/sqrt(ulp).  (0 means irrelevant.)
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **402** of file **sdrvev.f**.

## Author

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