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- MKL SPEVD documentation error and unknown error return--need help

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nvaneck

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09-21-2011
05:48 AM

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MKL SPEVD documentation error and unknown error return--need help

The call is:

use lapack95

REAL(8) R(MD,MD),E(MD),V(MD,MD),E1(MD),V1(MD,MD)

REAL(8) AP(MD*MD)

E1=0.

V1=0.

K=1

DO J=1,MD

DO I=J,MD

AP(K)=R(I,J)

K=K+1

END DO

END DO

CALL spevd(AP,E1,'L',V1,INFO)

where md is 21.

The documentaed call is:

Fortran 95:

call spevd(ap, w [,uplo] [,z] [,info])

and additionally states later:

Specific details for the routine spevd interface are the following:

ap Holds the array A of size (n*(n+1)/2).

w Holds the vector with the number of elements n.

z Holds the matrix Z of size (n, n).

uplo Must be 'U' or 'L'. The default value is 'U'.

jobz Restored based on the presence of the argument z as follows:

jobz = 'V', if z is present,

jobz = 'N', if z is omitted.

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7 Replies

mecej4

Black Belt

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09-21-2011
06:35 AM

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If you provide a complete, self-contained example that exhibits the problem, I can look at it. On the other hand, code fragments with unknown argument values are not enough to get started with probing for causes of aborts.

Steven_L_Intel1

Employee

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09-21-2011
06:41 AM

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nvaneck

New Contributor I

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09-21-2011
07:20 AM

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mecej4

Black Belt

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09-21-2011
08:57 AM

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That is an undesirable side effect of using the F95 interface. Since the argument list does not contain *n, *the number of rows (or columns) of the matrix, the value of *n* has to be deduced from the size of the packed array by solving a quadratic equation for *n*, ( *n (n + 1) /2* = length of array*Ap*) as we can see in the source files sspevd.f90and dspevd.f90.

The documentation says

That does not apply to the F95 interface, for which "at least" should be removed. I hope that one of the Intel people will take note of this.

Vladimir_Koldakov__I

New Contributor III

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09-22-2011
02:00 AM

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Hi,

The info argument returns the number of argument of original Fortran 77 interface. So the argument -7 corresponds here to LDZ argument that is skipped in the Fortran 95 interface.

And really, *at least* does not apply to Fortran 95 arrays. All F95 arrays must have exact dimensions. MKL documentation claims:

Input arguments such as array dimensions are not required in Fortran95 and are skipped from the calling sequence. Array dimensions are reconstructed from the user data that must exactly follow the required array shape.

Thanks,

Vladimir

Gennady_F_Intel

Moderator

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09-22-2011
04:06 AM

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ok, thanks. we have got it.

yuriisig

Beginner

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09-22-2011
06:11 AM

75 Views

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