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ZTFSM issues (rectangular full packed storage triangular matrix solve)

shughey
Beginner
258 Views

Hi,

I am hoping to use ZTFSM to solve a triangular system in the RPF/RFP format with and without transposition, i.e., A*X=B and A^T * x = B, where A is a triangular matrix stored in RFP format. The routine appears to function properly when trans = 'N', but when I specify trans = 'T' to solve the transpose problem A^T * X = B, I get the error "Intel MKL ERROR: Parameter 4 was incorrect on entry to ZTFSM ."

I also tried to hack around this issue by conjugating A and using trans = 'C' to denote the conjugate transpose. This results in an error on the order of 1e-3 for a 4x4 matrix.

Note that I am only changing the 'trans' flag; all other parameters remain fixed.

Am I using ZTFSM incorrectly? Is this a known bug?

 

Thanks

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4 Replies
ShanmukhS_Intel
Moderator
240 Views

Hi,

 

Thanks for posting on Intel Communities. Kindly refer below link for usage regarding ZTFSM.

 

https://www.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-fortran/top...

 

In addition, Could you please share us a sample reproducer and steps(if any), so that we could try reproducing the issue at our end.

 

Best regards,

Shanmukh.SS

 

mecej4
Black Belt
232 Views

Since the MKL example files did not (?) contain a test file for the ?TFSM routines, I took the example provided by NAG and modified it for use with MKL (remove references to NAG modules, provide parameter declaration for the real kind _wp, and replace the call to x04... by a simple PRINT *,IFAIL). The program ran and produced the correct result, using the current version of IFort and MKL (OneAPI 2022).

 

Please provide a reproducer.

shughey
Beginner
224 Views

I think I figured out my mistake. I did not realize until reading the documentation for ZTRTTF that MKL expects the lower right triangle to be stored in conjugate-transpose form, rather than in transpose form. Things are working now. Sorry for the confusion, and thank you for the quick responses!

Gennady_F_Intel
Moderator
185 Views

This issue has been resolved and we will no longer respond to this thread. If you require additional assistance from Intel, please start a new thread. Any further interaction in this thread will be considered community only. 



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