# Which software packages can solve linear systems that are not stored

I have matrices that are extremely easy to compute pointwise, but are too large to store. (they are not sparse) On the MATLAB site I was told MATLAB doesnt support computations with non-stored matrices. Is their any other software package out there that does?

• I assume that with storing you are referring to RAM, but the matrix would stored on a HHD? Or do you have a function which can calculate the value of a given index of the matrix? Mar 11, 2015 at 21:28
• How big are the matrices? If the matrices are so big that they can't be stored explicitly, yet are dense, wouldn't even forming matrix-vector products be overly expensive? PETSc can work with non-stored matrices. Mar 11, 2015 at 21:55
• the matrix can be calculated by indices Mar 11, 2015 at 21:56
• Where does the linear system of equations come from? In many cases large dense systems of equations have structure that can be exploited by specialized methods, but these methods depend on the particular structure of the system of equations, so you'd need to start by telling us where the equations came from. Mar 12, 2015 at 1:16
{"ft_lang_label":"__label__en","ft_lang_prob":0.9465405,"math_prob":0.9625659,"size":3408,"snap":"2023-40-2023-50","text_gpt3_token_len":772,"char_repetition_ratio":0.13836662,"word_repetition_ratio":0.014184397,"special_character_ratio":0.22564554,"punctuation_ratio":0.083596215,"nsfw_num_words":0,"has_unicode_error":false,"math_prob_llama3":0.9941293,"pos_list":[0],"im_url_duplicate_count":[null],"WARC_HEADER":"{\"WARC-Type\":\"response\",\"WARC-Date\":\"2023-10-05T03:16:33Z\",\"WARC-Record-ID\":\"<urn:uuid:373971c9-2928-4eae-9011-fe54b2a614c7>\",\"Content-Length\":\"177082\",\"Content-Type\":\"application/http; msgtype=response\",\"WARC-Warcinfo-ID\":\"<urn:uuid:d2d58433-083b-4c0c-998f-9fb91e7a29a0>\",\"WARC-Concurrent-To\":\"<urn:uuid:53921872-8df3-43e7-a0d6-a804952803cd>\",\"WARC-IP-Address\":\"104.18.10.86\",\"WARC-Target-URI\":\"https://scicomp.stackexchange.com/questions/19141/which-software-packages-can-solve-linear-systems-that-are-not-stored\",\"WARC-Payload-Digest\":\"sha1:UD2SSGEKIXGLDM7FEM7NQOX27LI2AACK\",\"WARC-Block-Digest\":\"sha1:4IBF34P5E6DDW27BOHMEX6CR7FHTZJ6S\",\"WARC-Identified-Payload-Type\":\"text/html\",\"warc_filename\":\"/cc_download/warc_2023/CC-MAIN-2023-40/CC-MAIN-2023-40_segments_1695233511717.69_warc_CC-MAIN-20231005012006-20231005042006-00414.warc.gz\"}"}