<html aria-label="message body"><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;"> It appears that only MATSOLVERMKL_CPARDISO provides a parallel backward solve currently. <div><br></div><div> The only seperation of forward and backward solves in MUMPS appears to be provided with (from its users manual)</div><div><br></div><div><p class="p1" style="margin: 0px; font-width: normal; font-size: 9px; line-height: normal; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">A special case is the one</p><p class="p1" style="margin: 0px; font-width: normal; font-size: 9px; line-height: normal; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">where the forward elimination step is performed during factorization (see <span class="s1" style="color: rgb(0, 11, 108);">Subsection 3.8</span>), instead of</p><p class="p1" style="margin: 0px; font-width: normal; font-size: 9px; line-height: normal; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">during the solve phase. This allows accessing the L factors right after they have been computed, with a</p><p class="p1" style="margin: 0px; font-width: normal; font-size: 9px; line-height: normal; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">better locality, and can avoid writing the L factors to disk in an out-of-core context. In this case (forward</p><p class="p1" style="margin: 0px; font-width: normal; font-size: 9px; line-height: normal; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><br></p><p class="p1" style="margin: 0px; font-width: normal; font-size: 9px; line-height: normal; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><br></p><div><br><blockquote type="cite"><div>On Nov 15, 2025, at 9:17 AM, Yin Shi via petsc-users <petsc-users@mcs.anl.gov> wrote:</div><br class="Apple-interchange-newline"><div><div>Dear Developers,<br><br>In short, I need to explicitly use A.solveBackward(b, x) in parallel with petsc4py, where A is a Cholesky factored matrix, but it seems that this is not supported (e.g., for mumps and superlu_dist factorization solver backend). Is it possible to work around this?<br><br>In detail, the problem I need to solve is to generate a set of correlated random numbers (denoted by a vector, w) from an uncorrelated one (denoted by a vector n). Denote the covariance matrix of n as C (symmetric). One needs to first factorize C, C = L L^T, and then solve the linear system L^T w = n for w in parallel. Is it possible to reformulate this problem for it to be implemented using petsc4py?<br><br>Thank you!<br>Yin</div></div></blockquote></div><br></div></body></html>