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--- projekt:rudel:grovinventering:riemann [2020/11/08 19:04] – pontus
+++ projekt:rudel:grovinventering:riemann [2021/05/27 19:39] – pontus
@@ Line 14: / Line 14: @@
 **Donator:** Matematiska institutionen
-**Kontaktperson(er):** En eller fler som kan veta mer! Kontakta gärna.
+**Tillbehör:** Dokumentation
+**Kontaktperson(er):** Dennis A. Hejhal
+Länkar till Dennis hemsidor (som omnämner Riemann och visar bilder):
+     *  http://www-users.math.umn.edu/~hejhal/index.work.html
+     * http://infolab.stanford.edu/~wangz/home/link/hejhal/index.pict.html
+Utvalda bilder:
+    * http://wang.ist.psu.edu/~jwang/home/photo/hejhal/1139.jpg
+    * http://infolab.stanford.edu/~wangz/home/link/hejhal/photo/1999/1999-05.jpg
+    * http://infolab.stanford.edu/~wangz/home/link/hejhal/photo/stanford/pictures/9709/jzw.9709.1.jpg
+Länk till UNT om utställningen på gustavianum:
+    * https://www.svt.se/nyheter/lokalt/uppsala/historiska-minidatorer-stalls-ut
+Plakat som användes vid utställningen "Tre ton minidatorer":
+    * {{ :projekt:tre_ton_minidatorer:a3-3ton-Riemann.pdf | Riemann }}
+    * {{ :projekt:tre_ton_minidatorer:a3-3ton-Riemann-koppling.pdf | Riemann och Uppsala Universitet }}
+    * {{ :projekt:tre_ton_minidatorer:a4-3ton-riemann-tech.pdf | Riemann Tekniskt }} |
+Information från Dennis:
+<file>
+            Information about "Riemann"
+            ===========================
+(I) Machine Specifications.
+CRAY YMP-EL4/1024
+(serial number:  SN 5125)
+The YMP-EL4/1024 was a parallel-vector machine having
+a maximum speed of 532 million operations per second.
+processors
+Gigabyte (1024 Megabytes) of memory for use in codes
+Gigabyte disk storage
+Operated:  October 1996 thru April 2001
+   by Prof. Dennis Hejhal's research group in the Uppsala
+   University Mathematics Department
+Total Purchase Price:  approximately 700000 SEK
+   (about 400k for the hardware, 300k for the software,
+    all paid for via a grant from NFR, i.e. current-day VR)
+Donated to the Update Computer Club:  mid-April 2001
+Machine age in 1996:  about 4 years old
+Previous Owner:  LOTUS Sports Cars Co. in UK
+Software:  Fortran77, Cray Fortran, Fortran 90, C, C++,
+           MAPLE, PVM, Cray Message Passing Toolkit (MPT)
+Operating System:  UNICOS  (like Unix)
+Clock period: 30 nanoseconds  (33 Megaherz)
+-------------------------------------------------------------
+      The machine's architecture allows, due to vectorization,
+      a peak performance per processor of 4 floating point
+      operations per clock period, which equates to 133 megaflops
+      (i.e., 133 million floating point operations per second).
+      Programs could also be run utilizing all 4 processors
+      in parallel.  For this, Riemann was equipped with both
+      a) Cray microtasking/autotasking software [for "fine-grained"
+      parallelism of do-loops];
+      b) PVM and MPT [for "large-scale" parallelism within codes].
+      Used in parallel, the theoretical maximum speed was thus 532
+      megaflops. In practice, on a good parallel code with lots of
+      numerical calculation (as opposed to i/o), Riemann ran about
+% faster than one CRAY-XMP processor, and frequently as fast
+      as one (mainframe) YMP processor.
+The following "per processor" table offers a comparison with other
+s-era parallel-vector machines manufactured by Cray:
+XMP - 8.5  nanosecond (117 Mhz) clock, 2 results per clock:  234 Mflops
+YMP - 6.0  nanosecond (166 Mhz) clock, 2 results per clock:  333 Mflops
+J90 -10.0  nanosecond (100 Mhz) clock, 2 results per clock:  200 Mflops
+C90 - 4.16 nanosecond (240 Mhz) clock, 4 results per clock:  960 Mflops
+EL - 30.0  nanosecond (33 Mhz)  clock, 4 results per clock:  133 Mflops
+Two machines here give 4 results per clock:  the C90 does this via dual
+vector pipes (all vectors run at 2 results per clock);  the Y-MP EL
+gets this from 4 independent functional units.
+(II) Scientific Information.
+During 1996-2001, Riemann was heavily used in Dennis Hejhal's Uppsala
+University research group on analytic number theory and quantum chaos.
+Notable experiments carried out on Riemann include:
+a) The detailed calculation of numerous quantum "vibrational" states
+linked to either prime number symmetries or lattices in negatively curved
+space.  For several years, Riemann held the world-record in the obtaining
+the states of highest energy in each context.
+b) The first-ever calculation of what are called "L-functions" associated
+with such quantum states.  These functions help mathematicians understand
+how much randomness is present in the associated vibrational pattern.  This,
+in turn, has important connections with the distribution of the prime numbers.
+In order to obtain these results, it was not uncommon that Riemann needed to
+run in dedicated mode (i.e., uninterruptedly) for one week or more.
+In addition to Hejhal, researchers involved in this work included Helen
+Avelin, Fredrik Stromberg, Andreas Strombergsson, and Holger Then.
+/31/2012
+</file>