The Bucknell Logical Systems C Handbook
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1. allocate channels here allocate process sorti two parameters chans a and y if sort1i ProcAlloc Sort1 WS_SIZE 2 a y NULL 17 printf No Memory for process Sorti n allocate process sort2 two parameters chans b and z if sort2 ProcAlloc Sort1 WS_SIZE 2 b z NULL printf No Memory for process Sort2 n ProcPar sort1 sort2 merge NULL This however led to inconsistent results At times the program would sort and merge the list correctly at others it would have elements which were incorrectly placed The problem here was the use of the static array The solution from last section was the cause of the problem this time Since the function Sort1 is instantiated in both sort1 and tt sort2 and the declaration is static the processes share the same storage for array A The proper solution here is just to remove the static from the declaration This will not create a memory problem as before since the memory used for the process is the stack space created when you do the ProcAlloc command The problem here is actually of a much broader scope any local function which may be called by two or more concurrent processes must be re entrant To insure that a function is re entrant it should be written with no static or global variables and no T 0 memory registers In other words ALL write variables must be volatile or stack based 2 12 Conclusion Many of the pro2. file for the above diagram 1 print RO O 211 2 p3 Ri 1 21 311 410 3 pi R2 sall s 4 p2 S2 2 31 S Z 2 6 Generating Random Numbers and Timing Programs in LSC This section is for the student who needs either to generate random values in Logical Systems C or to time code which is written in Logical Systems C For reference see Logical Systems C for the Transputer Version 89 1 User Manual 2 6 1 Random Numbers Generating numbers in Logical Systems is very simple First the user must include stdlib h in his or her program Defined within this library are three useful functions srand rand 7 and frand The first of these functions takes an unsigned integer as a parameter This function will set the seed for the pseudo random number generator The functions rand and frand return an integer random number and a floating point random number in the range 0 0 lt x lt 1 0 respectively 2 6 2 Timing Timing sections of code is essentially very easy in Logical Systems C Two functions SetTime and Time are provided in order to help the programmer The first SetTime takes an integer as a parameter this integer is what the timer in ticks for the current priority level will be set to The second Time takes no parameters but instead returns the value of the timer in ticks for the current priority level These two functions are defined in conc h which must be included in the program The only other bit
3. for exam4 c Dan Hyde April 23 1991 1 ex4 RO O 201 2 ex4 Ris a Tl 5 The above code demonstrates a simple approach to using C on multiple Transputers We have one process running on each Transputer and we communicate on the link channels directly This means we don t have to worry about creating new processes or creating new channels boot chan out and boot chan in are the channels used to boot the Transputer Therefore you can be sure they are connected to a neighboring Transputer which is closer to the SUN host Notice that by using the node number variable we can write one program which we run on many Transputers This may be wasteful of memory space but makes programming easier 2 5 How to Make and Use nif Files in Logical Systems C The nif extension on a file stands for network information file This file gives information about Transputer links to the network program loader 1d net used by Logical Systems C It is therefore very important that you create the nif files with careful deliberation 2 5 1 Form of nif file The file is organized as a sequence of node descriptions one per line ending with a The node description will take the following form node program name parent node link 0 link 1 link 2 link 3 2 5 2 Field 1 Node Number The node number can be a number of the user s choice This number must be a positive integer and may range from 1 to 1000 Non consecutive numbers may be u
4. laminin g gn 4 R Satta ep go RO 10 2526 Example mit Biles fee wank ad oda O Suara A A tet Ae as o RS 11 2 6 Generating Random Numbers and Timing Programs in LSC 00 11 2 6 1 Random Numbers a seror gei io d K ee 11 D Timing E 11 2 6 3 Sample Code ea ra 664 pp bb we a a TR TR p aeaaea e 12 2 7 Debugging LSC Programs 12 2 8 Common Pitfalls in Logical Systems CO o e 13 2 9 INTO UCA AA SN A A A ek RA A ds Yo 13 2 10 Student Misunderstandings 2 0 2 e 13 2 10 1 The ProcAlloc Statement 2 a 13 2 10 2 ProcRun vs E POG aR eyed kee oo Be A ee ee 14 2 10 3 ChanIn and Chan Out 4 weenie alee A ee ee eae Po eS 15 2 11 Logical Systems C Quirks a 16 2 11 1 Arrays in Sequential Processing e 2 1U1 2 Array Problem Revisited e K DA2QICONCIISION ia ao ad ls de At Ae ao ok Gh Ed ad a ala T T E K ea de 1 Introduction This manual describes the running of Logical Systems C programs on Bucknell University s Transputer network The Transputer network consists of four Inmos B014 boards installed in a Sun 3 server called hydra The four boards are populated with T800 Transputers The students access the Transputer network by way of the Department of Computer Science s Sun network which consists of about 40 Sun3s and Sunda While some of the material is implementation dependent much of the material would be useful to others using Logical System C in a Sun environment
5. print NULL ProcFree print This will spawn an instance of the print process and then block execution of the calling process until the print process has completed its execution 2 10 3 Chann and ChanOut ChanIn and Chan0ut read write byte streams This is an important point to emphasize For example the following code would not send out the first 8 integers of the list int list 10 initialize to some values x 8 ChanOut out char list x The code sends out the first two integers in the list This is because each integer is 4 bytes To correct this we should use the following statement ChanOut out char list 4 x To send the whole list we can use the sizeof function For example Chan0ut out char list sizeof list Similarly we must be careful when we use ChanIn 16 2 11 Logical Systems C Quirks The following are particular quirks to Logical Systems C running on Transputers which I found unusual and undocumented 2 11 1 Arrays in Sequential Processing One of the first problems I encountered when using Logical Systems C for a simple sort program i e no concurrent processes was the allocation of stackspace for the main I had defined in the main function a local array A of integers to be of size 2000 Being used to programming on machines with virtual memory this was perfectly normal However this caused my program to just lock up on the Transputers After eliminating all other pos
6. s links e g LINK1IN when we allocated the processes test c Written by John Douglass Logical Systems C program to time communication between two Transputers include lt stdio h gt include lt stdlib h gt needed for rand function include lt conc h gt define WS_SIZE 8192 define TICKSPERSEC 15625 define NUM 100 number of messages to be sent processi Process p Channel in Channel out int x y int B NUM x ChanInInt in wait for start signal SetTime 0 ChanIn in char B sizeof B y Time printf n Time for communication is f seconds n float y float TICKSPERSEC printf n Received d random numbers from process 2 n n NUM for x 0 x lt NUM x printf t d n Blx process2 Process p Channel in Channel out int A NUM int i for i 0 i lt NUM i A i rand generate NUM random integers ChanOutInt out 1 send signal to start timing Chan0ut out char A sizeof A main if _node_number 1 Process p1 pi ProcAlloc process1 WS_SIZE 2 LINK2IN LINK20UT ProcPar p1 NULL else Process p2 p2 ProcAlloc process2 WS_SIZE 2 LINK1IN LINK10UT ProcPar p2 NULL Here is the test nif file for the program This is the test nif file for the test of communications John Douglass 6 15 92 1 test RO 0 s Te 2 test Ri 1 2 a 2 4 LSC E
7. same errors I did mostly from not reading carefully enough and to save you the hours of debugging which I took to find the errors 2 10 1 The ProcAlloc Statement The ProcAlloc statement is used to allocate a stack frame so that a new process may be executed A new process is allocated as follows from LSC Manual include lt conc h gt Process ProcAlloc func sp nparam pl p2 pn int func O int sp nparam ProcAlloc takes a pointer to a function that contains the code for the process The parameter sp indicates the amount of stack space required for the process Not being sure of what value to use I used 8192 as it is used in all the LSC Manual s examples Using 0 for the default value as suggested in the manual did not work nparam specifies the number of words of space to allocate off the stack space initially for parameters to the function p1 p2 pnis the list of parameters The name nparam is misleading as it is the number of words needed and not the number of parameters For example a double variable takes two words From my experience integer variables and channels take one word Arrays of integers and channels also take one word as only a pointer is passed A sample invocation of this statement PRINT Process p int a int b int c c lt a TL b print c here 4See Chapter 14 page 178 and Chapter 16 page 272 14 Process print process pointer x 5
8. The Bucknell Logical Systems C Handbook Dr Daniel C Hyde Computer Science Department Bucknell University Lewisburg Pennsylvania 17837 hyde bucknell edu February 8 1993 Copyright 1993 By Dr Daniel C Hyde Permission to copy without fee all or part of this manual is granted provided that the copies are not made or distributed for direct commercial advantage and this copyright notice appears on the first page Contents 1 Introduction 3 2 Using Logical Systems Parallel C 3 2 1 Running Ordinary C Programs on One Transputer 200000000004 3 2 1 1 To Setup Compile and Run 0 0000 0 3 21 2 kurthet Details td A hu E EL A a be 4 2 2 Running Concurrent C Programs on One Transputer o a 4 2 2 1 Using the LSC Concurrent Routines ee 4 2 2 2 Sample Concurrent Program 2 a 5 2 3 Running on a Network of Transputers 2 200 0 ee 6 2 3 1 Setting Board Topology a 6 2 3 2 Loading a Network of Transputers a 6 PAS ESC Examples 242 2 286 a Se hey e oly eae Pes Gok Acted ee eh ae ape a 8 2 5 How to Make and Use nif Files in Logical Systems C 9 Zo Form Of nit Mesu enik 2 ay aut AS see ee Ea 9 2 5 2 beld Dr Node Number odds E ARR A ee bale o aiai 9 2 5 3 Field 2 Program to Download e 9 2 04 Field 43 Parent Node ewe ms RR Ah pred ek eee Ta lap ha K K 10 2 5 5 Fields 4 7 Link Connections s s coda dearie D ERE a a a N N N 10 20 6
9. ZE 2 a b ProcPar p1 p2 p3 NULL ProcFree p1 ProcFree p2 ProcFree p3 2 3 Running on a Network of Transputers 2 3 1 Setting Board Topology Before you can run on multiple Transputers you must be using board 1 or board 4 and have set the topology of the Transputers hardware links on the board as described on page 24 of The Bucknell Transputer Handbook Using Inmos s Toolset 2 3 2 Loading a Network of Transputers To load a network of Transputers we use 1d net instead of 1d one 1d net requires a network information file with an nif extension This file is a simple description of Transputer node numbers the program to run on each and the connection of the links See the section on nif files on how to create them To run the below program we use 1d net with the test nif file ld net test Notice that we do not need the cio parameter which we used with 1d one The node_number those are underlines variable holds the network address for the processor which is running the program The declaration for mnode_number is in conc h Below is an example LSC program that runs on two Transputers By using node_number we distinguish at run time what code to execute This allows us to write one program and load it on both Transputers Or we could have easily used two separate files Notice that we did not need to allocate any channels as we used the predefined channels which correspond to the Transputer
10. blems I encountered when using Logical Systems C were simple misunderstandings It is best to read the documentation carefully before trying to program The above errors are just the problems which I had the most difficultly with and are certainly not all the pitfalls that you will encounter 6This is from a e mail message by Scott Cannon Department of Computer Science Utah State University who helped answer a question about LSC 18
11. e c do the following on a SUN 3 tcc mine lLogical Systems P O Box 1702 Corvallis OR 97339 This should create a file with a tld extension if there were no compiler errors 3 To load onto one Transputer do the following on the sun server hydra ld one mine cio where cio is the host server interface program This uses the tld file to load the Transputer start execution on the Transputer and interact with the screen and keyboard 2 1 2 Further Details You can redirect the input by ld one mine cio lt mydata You can redirect output by ld one mine cio gt myout To change between the four Transputer boards type b1 b2 b3 or b4 These are aliases in the setup file 2 2 Running Concurrent C Programs on One Transputer 2 2 1 Using the LSC Concurrent Routines To use the concurrent routines insert the following include file include lt conc h gt 2 2 2 Sample Concurrent Program Below is a Logical Systems C program which allocates three concurrent processes P1 P2 and P3 which all run on one Transputer The program allocates three channels which are used to send integers from P1 and P2 to P3 P3 uses an ProcAlt to determine which channel has a message then a ChanInInt to read it If you know Occam you can easily write Logical Systems C concurrent programs by using the constructs that correspond to Occam For channels you use the ChanAlloc ChanIn and ChanOut functions For concurrent processes you
12. e print and still get the correct values 2 10 2 ProcRun vs ProcPar Another error which I experienced was my incorrect use of ProcRun There are some subtle differences between the way in which ProcPar and ProcRun which I did not pick up when I read the manual Take for instance the following code Process print process pointer x 5 y 4 5See Chapter 14 pages 178 179 for use of ProcPar and ProcRun 15 if print ProcAlloc PRINT 8192 2 amp x amp y NULL exit 1 ProcPar print NULL ProcPar here is used to invoke an instance of the process PRINT Important to note is that this statement will block execution of the calling process until all of the procs in the list have completed This is different from ProcRun which takes only one process as an argument ProcRun will spawn a process and then allow the continuation of the calling process This difference can lead to hard to track down errors for instance Process print process pointer x 5 y 4 if print ProcAlloc PRINT 8192 2 amp x amp y NULL exit 1 ProcRun print ProcFree print In the above code an instance of the process PRINT is spawned by the ProcRun execution However the calling process then continues and executes the ProcFree statement which will free the process pointer This can cause very serious errors To avoid this error use the ProcPar statement with one process instead for instance ProcPar
13. ne using the notation For example 1 zip RO 0 2 1 3 2 In this example the root node 1 is loaded with program zip tld is reset by the system output of the host and its link 0 is connected to the host link 1 is connect to node 2 link 1 link 2 is connected to node 3 link 2 and link 3 is left unconnected 2 5 6 Planning Careful planning of the nif file at the beginning will increase your understanding of the file and possibly prevent you from experiencing errors in your program which occur not in the code but in the way in which you set the network links The first phase of this planning is to draw a diagram of your program showing the communication paths between your processes In this example there are four processes two which generate data and a third which merges this data and a fourth which prints it out a TS Sl b Figure 1 Process Diagram Now carefully map this diagram to a diagram of Transputers which each have four links Remember that the node one Transputer is the one which can do i o and that it s link 0 must go to node 0 Remember to set the topology of the Transputers 2see reference in Transputer Manual page 24 11 to host node 1 node 2 node3 node 4 3 l 2 2 Figure 2 Transputer mapping 2 5 7 Example nif File The following file would be a sample nif file for the above example nif
14. of information a person needs to know is that the timer runs at different rates for high 1 pS tick and low priority 64 uS tick processes This means that there are 1 000 000 ticks per second and 15 625 ticks per second respectively 3 You must use a capital T on this function name as time is a different function 12 2 6 3 Sample Code Here is an working example which demonstrates both random number generation and timing of code include lt stdio h gt include lt conc h gt include lt stdlib h gt define TICKSPERSEC 15625 for a low priority process main int runtime will store the elapsed time int A 100 array for random values int result temporary result int i j loop counters for i 0 i lt 100 i A il rand store rnd number in A i printf n About to reset the timer n SetTime 0 reset timer to zero for i 0 i lt 1000 i for j 0 j lt 100 j result A j 5 runtime Time printf The runtime is f seconds n float runtime float TICKSPERSEC 2 7 Debugging LSC Programs Output and input statements e g printf and scanf may only occur in the program running on the root Transputer Also all of the printf statements should appear in only one concurrent process When debugging concurrent LSC programs on one Transputer one may insert printfs in any concurrent process as long as no other process tries to print I
15. or an IBM PC compatable environment 2 Using Logical Systems Parallel C You will write programs in a parallel C developed by Logical Systems which compiles on the Sun3s and loads onto the Transputer network Extensions to the C language have been added for message passing between concurrent processes much like in Occam The extensions are in the form of library calls See pages 177 185 in Logical Systems C for the Transputer Version 89 1 User Manual available from Logical Systems 2 1 Running Ordinary C Programs on One Transputer 2 1 1 To Setup Compile and Run To run a C program on one Transputer do the following steps 1 Source the file logicalC setup or put the contents in your cshrc file X source logicalC setup Below is a copy of Bucknell s setup file setup file for Logical Systems C path of files is home hydra local LogicalC 1sc89 1 Installed March 27 1991 by Dan Hyde set path path home hydra local LogicalC 1sc89 1 setenv TMP usr tmp setenv PPINC home hydra local LogicalC 1sc89 1 include setenv TLIB home hydra local LogicalC 1sc89 1 library setenv LINKNAME dev bxiv0 the next four lines are for aliases to allow a user to switch from one board to another of the four B014 boards alias b1 setenv LINKNAME dev bxiv0 alias b2 setenv LINKNAME dev bxiv1 alias b3 setenv LINKNAME dev bxiv2 alias b4 setenv LINKNAME dev bxiv3 2 To compile and link a C file called min
16. sed but they must be distinct Node number 0 is reserved to represent the host interface i e the SUN By convention node number 1 should be the root Transputer in the network The node number provided in the nif file is available to the user during execution as the contents of the node_number external integer variable defined in conc h 2 5 3 Field 2 Program to Download Contains the name of the program to download to that particular node By default a file name extension of tld is assumed if none is specified 10 2 5 4 Field 3 Parent Node This field contains both the number of the parent node and an indication about whether the system or sub system output of the parent node controls the reset for this node System output is denoted by an R and sub system output is denoted by an S No more than one node may be connected to the system or sub system output of its parent node Since node number 0 is defined to be the host interface a field containing RO should be used with the root node to describe who resets it It is important that there exist a link between a node and it s parent node 2 5 5 Fields 4 7 Link Connections The last four fields in the line are used to specify which node each link is connected to If a link is unconnected its entry may be left blank a comma is still required as a place holder It is best to explicitly declare which link of the node you are connected to this is do
17. sibilities it was determined that the problem was the program was running out of memory I theorize that the stackspace was being stored in the Transputer s on chip memory and the array exceeded the 4 KBytes allowed To solve this problem I simply moved the declaration of the array to make it global This meant the array A was now being stored in the global stack space Another solution is to make A static this also has the effect of storing A not in the stack space but in the global area 2 11 2 Array Problem Revisited After having solved my array memory problem I went on to splitting my sequential sorting program into a concurrent version which used two sort processes and amerge The sort processes would send the results of sorting half a list to the merge which would merge the two halves into a final list These two sort processes were invoked from one process declaration For example Sorti Process p Channel out Channel in Intent sorts values and sends them to Merge int i loop index int n number of elements to generate static int A MAX n ChanInInt in receive value from merge GenArray A n generate n rnd elements Chan0utInt out 1 send start timer to merge Sort A n sort the arrays for i 0 i lt n i send values out Chan0utInt out A i Chan0utInt out 1 send done signal main Channel a b y Z Process sorti sort2
18. t is best to have a screen manager process which collects the debugging messages by way of a vector of channels and displays them on the screen Debugging on multiple Transputers is more difficult Always debug a concurrent version of the program on one Transputer before moving the program to a network of Transputers If you design your program with this move in mind the move should be straight forward When debugging programs on multiple Transputers always double check your nif file carefully If your program hangs concentrate first on getting the communication working between the Transputers Once that is working you can send debugging messages to the screen manager on the root Transputer 13 2 8 Common Pitfalls in Logical Systems C The following four sections were written by John Douglass of Bucknell University s class of 1992 2 9 Introduction This section documents some pitfalls which were discovered during a first experience with Logical Systems C It assumes the reader has a basic knowledge of C and has available as reference Chapters 14 15 and 16 of Logical Systems C for the Transputer Version 89 1 User Manual A previous knowledge of Occam is helpful but not required 2 10 Student Misunderstandings After having read Chapters 14 and 15 of Logical Systems C for the Transputer Version 89 1 User Manual I felt that I was ready to begin programming This section of the Handbook is designed to help prevent you from making the
19. use ProcAlloc ProcFree ProcAlt and ProcPar functions Of course Logical Systems C is more flexible than Occam as you can allocate and free processes at run time have recursive functions and dynamic memory allocation all which are not possible in Occam PE k kk k kkk kk kkk kkk k kkk file mine C2 A 2 akak ak k k Logical Systems C example with three concurrent processes P1 and P2 each send an integer to P3 P3 receives the integers and displays them By Dan Hyde July 24 1992 include lt stdio h gt include lt conc h gt define WS_SIZE 8192 work space size Pi Process p Channel out int y y 3 ChanOutInt out y P2 Process p Channel out int 2 z T Chan0utInt out z P3 Process p Channel in1 Channel in2 int which i x printf nStarting Program n for i 0 i lt 2 i which ProcAlt in1 in2 NULL if which 0 x ChanInInt in1 printf int d n x else x ChanInInt in2 printf in2 d n x printf nProgram termination n main Process p1 p2 p3 Channel a b c allocate channels a ChanAlloc b ChanAlloc c ChanAlloc allocate process p1 one parameter chan a pi ProcAlloc P1 WS_SIZE 1 a allocate process p2 one parameter chan b p2 ProcAlloc P2 WS_SIZE 1 b allocate process p3 two parameters chans a and b p3 ProcAlloc P3 WS_SI
20. xamples The Logical Systems C system comes with several examples The below code is a unmodified copy of exam4 c in the directory home hydra local LogicalC 1sc89 1 example This directory which came with the compiler has other examples you may want to look at We suggest you look at or try examl c exam4 c to exam9 c and pipe4 nif exam4 c file include lt stdio h gt include lt conc h gt main Channel chan int id 0 if _node_number 1 We are the root Transputer inform the user as the various node addresses arrive Note that we listen for input from the bootstrap link also but this doesn t matter since it shouldn t generate any output printf Root node ID was d n node_number printf Booted from input channel p n boot_chan_in while 1 chan LINKOIN int ProcAlt LINKOIN LINK1IN LINK2IN LINK3IN 0 printf nMessage on input channel p n chan ChanIn chan char amp id 2 printf Message was node ID dWn id else We are not the root look at all input links and send any node addresses we get out the link we were bootstrapped on ChanQut _boot_chan_out char amp _node_number 2 while 1 chan LINKOIN int ProcAlt LINKOIN LINK1IN LINK2IN LINK3IN 0 ChanIn chan char amp id 2 ChanQut _boot_chan_out char amp id 2 Here is a nif file for this example Network Information File
21. y 4 if print ProcAlloc PRINT 8192 2 x y NULL exit 1 ProcPar print NULL x 4 y 5 ProcPar print NULL This invocation will allocate stack space for the process PRINT and assign it to the process pointer print You then start the process by using the ProcPar or the ProcRun command The important thing to note here is that the execution of the ProcAlloc statement binds the actual param eters a and b to the current values of the formal parameters x and y In the above example both the first and second executions of ProcPar will send the PRINT process x 4 and y 5 even though their values have been modified before the second call One solution to this problem is to invoke ProcAlloc again after the modification of z and y However this solution produces unnecessary overhead A better solution to this problem is to use call by reference In C this means that we must place an amp before x and y in the ProcAlloc statement and a x before instances of a and b in the PRINT function For example PRINT Process p int a int b int c c a b print c here Process print process pointer x 5 y 4 if print ProcAlloc PRINT 8192 2 amp x amp y NULL exit 1 ProcPar print NULL x 4 y 5 ProcPar print NULL This invocation binds the addresses of x and y and the x before the a and b dereferences these Now we can modify x and y and reinvok
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