<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><br><div><br></div><div> <a href="https://petsc.org/release/manualpages/Mat/MatPtAP/">https://petsc.org/release/manualpages/Mat/MatPtAP/</a> also note that PETSc has a large infrastructure for efficient ways to compute various matrix-matrix operations with a variety of algorithms that can be all accessed by starting with <a href="https://petsc.org/release/manualpages/Mat/MatProductCreate/">https://petsc.org/release/manualpages/Mat/MatProductCreate/</a></div><div><br></div><div><br><blockquote type="cite"><div>On Jul 17, 2023, at 1:13 PM, Karthikeyan Chockalingam - STFC UKRI via petsc-users <petsc-users@mcs.anl.gov> wrote:</div><br class="Apple-interchange-newline"><div><meta charset="UTF-8"><div class="WordSection1" style="page: WordSection1; caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 18px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Hello,<o:p></o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">I would like to perform the following operation<o:p></o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">[P^T A P] x’ = P^T f<o:p></o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Where P is a rectangular matrix and A is a square matrix. All the matrixes are constructed using MPIAIJ.<o:p></o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Should I be concerned about the parallel partitioning of the matrix P and A?<o:p></o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Or can I just go ahead and use MatMatMult to compute [P^T A P]?<o:p></o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Is there any in-built functionality to perform this operation?<o:p></o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Kind regards,<o:p></o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;">Karthik.<o:p></o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><span>-- <o:p></o:p></span></div></div><div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><b><span style="font-size: 10.5pt; font-family: Arial, sans-serif; color: rgb(45, 45, 98);">Dr. Karthik Chockalingam</span></b><span style="color: rgb(33, 33, 33);"><o:p></o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><span style="font-size: 10.5pt; font-family: Arial, sans-serif; color: rgb(65, 65, 65);">High-Performance Software Engineer</span><span style="color: rgb(33, 33, 33);"><o:p></o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><span style="font-size: 10.5pt; font-family: Arial, sans-serif; color: rgb(65, 65, 65);">Hartree Centre | Science and Technology Facilities Council</span><span style="color: rgb(33, 33, 33);"><o:p></o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><span style="font-size: 10.5pt; font-family: Arial, sans-serif; color: rgb(33, 33, 33);"><a href="mailto:karthikeyan.chockalingam@stfc.ac.uk"><span style="color: rgb(5, 99, 193);">karthikeyan.chockalingam@stfc.ac.uk</span></a></span><span style="color: rgb(33, 33, 33);"><o:p></o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><span style="font-size: 12pt; font-family: "Times New Roman", serif;"> </span><span style="font-size: 10.5pt; font-family: Arial, sans-serif; color: rgb(65, 65, 65);"> </span><span style="color: rgb(33, 33, 33);"><o:p></o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;"><b><span style="font-size: 10.5pt; font-family: Arial, sans-serif; color: rgb(65, 65, 65);"> </span></b><span style="font-size: 12pt; font-family: "Times New Roman", serif; color: rgb(31, 73, 125);"><span id="cid:image001.png@01D9B8D7.C690AD30"><image001.png></span></span></div></div></div></div></div></blockquote></div><br></body></html>