# Questions tagged [blas]

Basic Linear Algebra Subprograms - A standard API library with vector-vector, matrix-vector, and matrix-matrix operations.

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### Matrix Diagonalization and Computational Requirements

I have some questions about diagonalizing matrices. My interest lies in computing all eigenvalues of a given matrix. To avoid wasting time and improve my research efficiency, I want to understand the ...
• 143
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### Weird runtime behavior of scipy.linalg.solve_triangular and trtrs

I want to understand the time complexity of scipy.linalg.solve_triangular, which calls trtrs from LAPACK under the hood, so I ...
• 181
1 vote
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### How do BLAS libraries implement support for transposed matrices?

I'm trying to understand how BLAS libraries implement fast GEMM with support for transposed matrices. Say, I'm only operating on square matrixes (with dimensions n ...
• 121
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### What is the correct way of computing $LL^T$ in packed format with blas/lapack

I have a triangular matrix stored in packed format (ie $L$). I need to compute $LL^T$ (not the decomposition, just the multiplication). What would be the preferred way of computing this with blas/...
• 23
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### Is it possible to express an arbitrary tensor contraction in terms of BLAS routines?

I noticed that libraries like numpy and pytorch are able to perform arbitrary tensor contractions at speeds similar to comparably sized matrix multiplications. This leads me to believe that underneath ...
• 121
186 views

### Fast weighted vector inner product x*A*y with BLAS/LAPACK

Is there a way to compute the weighted vector inner product xAy with vectors x and y and Matrix A using BLAS/LAPACK while avoiding additional allocations or overwriting the inputs? I'm happy with ...
• 799
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### Using Sundials CVODE in MATLAB

I'm currently using ode15s to solve a set of stiff differential equations. I am trying to use the MATLAB profiler to understand the section of the ode solver code which calls BLAS routines. Since the ...
• 433
1 vote
97 views

### Automatic differentiation (AD) of a loss function which maps unitary matrix onto number

Is it possible to estimate whether automatic differentiation (AD) techniques could enable a more efficient way to repeatedly compute the derivative $\delta L / \delta u^*_{ij}$ of a specific loss ...
• 111