SPPTRS(3)

💖 NAME 💖

SPPTRS(3) is chilling in the Library Functions Manual, and the NAME section is literally this source path, no cap: /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/spptrs.f.

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✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

• subroutine SPPTRS (uplo, n, nrhs, ap, b, ldb, info) — yep, that’s the whole icon.

🦋 Function/Subroutine Documentation 🦋

The full signature is giving main-character energy:

subroutine SPPTRS (character uplo, integer n, integer nrhs, real, dimension(
       * ) ap, real, dimension( ldb, * ) b, integer ldb, integer info)

Also: SPPTRS. 💅

🌸 Purpose 🌸

Okay so SPPTRS solves a system of linear equations A*X = B with a symmetric positive definite matrix A in packed storage using the Cholesky factorization A = U**T*U or A = L*L**T computed by SPPTRF. That’s the whole assignment, bestie. 🎀

The source comments are all wrapped in !> markers, which is lowkey their love language.

✨ Parameters ✨

• UPLO — is CHARACTER*1; = 'U': upper triangle of A is stored; = 'L': lower triangle of A is stored. Pick your triangle, queen. 🎀
• N — is INTEGER; the order of the matrix A. N >= 0. Zero is valid, bestie.
• NRHS — is INTEGER; the number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0. Again: zero is allowed.
• AP — is REAL array, dimension (N*(N+1)/2); the triangular factor U or L from the Cholesky factorization A = U**T*U or A = L*L**T, packed columnwise in a linear array. The j-th column of U or L is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = U(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = L(i,j) for j<=i<=n. That indexing is a lot, but she ate. 🔥
• B — is REAL array, dimension (LDB,NRHS); on entry, the right hand side matrix B; on exit, the solution matrix X. Glow-up moment: B comes in, X goes out. ✨
• LDB — is INTEGER; the leading dimension of the array B. LDB >= max(1,N). Respect the leading dimension, periodt.
• INFO — is INTEGER; = 0: successful exit; < 0: if INFO = -i, the i-th argument had an illegal value. So if it’s negative, it’s snitching on which arg was bad. 💀

🫶 Author 🫶

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

Also: Definition at line 107 of file spptrs.f. — that’s where she lives, iykyk.

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🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code. Slay, robot-generated documentation. 🤖✨

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💖 Cute little sign-off: this is LAPACK Version 3.12.0, and the page path is /home/abui...RC/spptrs.f(3). Byeee, go solve those linear systems! 🎀🦋