### LINPACK - why should LDA > N?

Posted:

**Tue Mar 07, 2017 11:46 pm**In reviewing the extended help from Intel, I have a question.

Specifically, leading dimension of array: The documentation says:

"The leading dimension must be no less than the number of equations. Experience has shown that the best performance for a given problem size is obtained when the leading dimension is set to the nearest odd multiple of 8 (16 for Intel(R) Itanium(R) 2 processors) equal to or larger than the number of equations (divisible by 8 but not by 16, or divisible by 16 but not 32 for Intel(R) Itanium(R) 2 processors)."

Why is that the case for best performance? Do you have any details as to how that is connected with cache line size? Trying to understand how having a LDA = N+8 would be beneficial.

Thanks!!

Specifically, leading dimension of array: The documentation says:

"The leading dimension must be no less than the number of equations. Experience has shown that the best performance for a given problem size is obtained when the leading dimension is set to the nearest odd multiple of 8 (16 for Intel(R) Itanium(R) 2 processors) equal to or larger than the number of equations (divisible by 8 but not by 16, or divisible by 16 but not 32 for Intel(R) Itanium(R) 2 processors)."

Why is that the case for best performance? Do you have any details as to how that is connected with cache line size? Trying to understand how having a LDA = N+8 would be beneficial.

Thanks!!