Basic Linear Algebra Subprograms - A standard API library with vector-vector, matrix-vector, and matrix-matrix operations.
1
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1answer
41 views
Does scalapack need threaded or unthreaded blas?
I'm compiling a blas to use with scalapack. Some blases, such as openblas, are naturally multithreaded, but scalapack uses mpi, so maybe needs a single-threaded blas? My questions then are:
does ...
4
votes
1answer
32 views
How to do transpose for trtrs (or tptrs) in blas?
How to do transpose for trtrs (or tptrs) in blas?
I want to solve:
XA = B
But it seems that trtrs only lets me solve:
...
5
votes
1answer
95 views
Reference BLAS/LAPACK from NETLIB is twice as fast as MKL for complex numbers
I'm solving the Helmholtz equation using PETSc. I found with the PETSc configure option --download-f-blas-lapack my program runs twice as fast over running it with ...
2
votes
1answer
71 views
Intel MKL - Difference between mkl_intel_lp64 and mkl_gf_lp64
I am currently trying to link a program against the Intel MKL 11.0 library instead of using NetLIB or OpenBLAS. Doing this I recognized the following error which I can not explain to my self at the ...
4
votes
1answer
203 views
Threaded OpenBlas benchmark slower than system blas?
I'm not sure if I did something wrong or if I just didn't understand the concept of an optimized BLAS.
I'm a FEM engineer trying to optimize my setup on a small cluster computer (six nodes). I'm ...
1
vote
1answer
90 views
Understanding Inner blocking size in lapack/plasma
I could not get accurate description that aids to my understanding of inner blocking size parameter that is used in many LAPACK routines(such as DGEQRT, DLARFB).
Thanks
4
votes
1answer
168 views
Magma vs. Plasma
I'm having a difficult time understanding the difference between the linear algebra packages MAGMA and PLASMA from just a quick glance. It looks like MAGMA is oriented towards GPU's and vector ...
9
votes
2answers
291 views
What are the fastest available implementations of BLAS/LAPACK or other linear algebra routines on GPU systems?
nVidia, for example, has CUBLAS, which promises 7-14x speedup. Naively, this is nowhere near the theoretical throughput of any of nVidia's GPU cards. What are the challenges in speeding up linear ...
3
votes
2answers
93 views
Efficiently changing basis on many diagonal matrices
I have to perform a [complex] basis transformation on a large number of [real] diagonal matrices:
$$ \langle b_i | A | b_j \rangle = \sum_k \langle b_i | \bar{b}_k\rangle \langle\bar{b}_k | A | ...
7
votes
1answer
92 views
Sudden drops in matrix multiplication performance
I've been reading about implementing dense matrix multiplication when the matrix doesn't fit in cache. One of the graphs I've seen (slide 9 from these slides) shows sudden drops in performance using ...
-1
votes
1answer
336 views
BLAS/LAPACK subroutine to add two matrices with different offsets and leading dimensions
I currently searching for a subroutine from BLAS or LAPACK which realizes the following operation
A = alpha*A + beta * B
where A and B have different leading ...
8
votes
1answer
210 views
Does PETSc ever make use of LAPACK libraries for sparse matrix math?
Does compiling PETSc with an external BLAS/LAPACK library significantly affect performance on sparse matrices, or does it only use those libraries for dense matrix math?
4
votes
1answer
153 views
Estimating time for running serial/parallel codes
Assume I am running an iterative method, I have a rough estimate of how many iterations it will need, How do best estimate the time it will run for in serial?
For instance, If I have Conjugate ...
5
votes
3answers
528 views
Are DAXPY, DCOPY, DSCAL overkills?
I have implemented CG in FORTRAN by linking it to Intel MKL.
When there are statements like:
(Refer Wikipedia)
p=r;
x=x+alpha*p
r=r-alpha*Ap;
or similar ...
10
votes
3answers
468 views
Why isn't my Matrix-Vector Multiplication Scaling?
Sorry for the long post but I wanted to include everything that I thought was relevant in the first go.
What I want
I am implementing a parallel version of Krylov Subspace Methods for Dense ...
4
votes
2answers
935 views
How do I use ScaLapack/PBLAS for Matrix-Vector Multiplication?
After going to all possible "Introductions" to ScaLapack, I still can't understand how to carry out a simple PDGEMV operation using it.
Here is what I must do :
...
29
votes
4answers
3k views
How much better are Fortran compilers really?
This question is an extension of two discussions that came up recently in the replies to "C++ vs Fortran for HPC". And it is a bit more of a challenge than a question...
One of the most often-heard ...
10
votes
2answers
424 views
How useful is PETSc for Dense Matrices?
Wherever I have seen, PETSc tutorial/documents etc. say that it is useful for linear algebra and usually specifies that sparse systems will benefit. What about dense matrices? I am concerned about ...
5
votes
2answers
143 views
Is it possible to use BLAS if I have a function rather than a matrix?
My matrix sizes have grown beyond what can fit on the RAM but I have a function which defines each element cheaply.
Is it possible use BLAS (in Fortran or even in MATLAB) in such cases?
If I had a ...
