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  • suggest an algorithm for the following puzzle!!

    - by garima
    There are n petrol bunks arranged in circle. Each bunk is separated from the rest by a certain distance. You choose some mode of travel which needs 1litre of petrol to cover 1km distance. You can't infinitely draw any amount of petrol from each bunk as each bunk has some limited petrol only. But you know that the sum of litres of petrol in all the bunks is equal to the distance to be covered. ie let P1, P2, ... Pn be n bunks arranged circularly. d1 is distance between p1 and p2, d2 is distance between p2 and p3. dn is distance between pn and p1.Now find out the bunk from where the travel can be started such that your mode of travel never runs out of fuel.

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  • 3D points to quaternions

    - by Hubrus
    For the simplicity, we'll consider two 3D points, that moves one relatively to other, in time. Let's say: at moment t0, we have P1(0,0,0) and P2(0,2,0) at moment t1, P1 is still (0,0,0) but P2 changed to (0,2,2). From what I've understood reading about quaternions, is that, at moment t0, Q1 (representing P1) and Q2 (representing P2) will be both (0, 0, 0, 0). But at the moment t1, Q2 will become something else (w, x, y, z). How do I calculate the Q2 at t1 moment? I've googled a lot on this subject, but I was able to find only rotation between quaternions. I will appreciate any guidance. Thanks!

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  • NHibernate Pitfalls: Fetch and Paging

    - by Ricardo Peres
    This is part of a series of posts about NHibernate Pitfalls. See the entire collection here. NHibernate allows you to force loading additional references (many to one, one to one) or collections (one to many, many to many) in a query. You must know, however, that this is incompatible with paging. It’s easy to see why. Let’s say you want to get 5 products starting on the fifth, you can issue the following LINQ query: 1: session.Query<Product>().Take(5).Skip(5).ToList(); Will product this SQL in SQL Server: 1: SELECT 2: TOP (@p0) product1_4_, 3: name4_, 4: price4_ 5: FROM 6: (select 7: product0_.product_id as product1_4_, 8: product0_.name as name4_, 9: product0_.price as price4_, 10: ROW_NUMBER() OVER( 11: ORDER BY 12: CURRENT_TIMESTAMP) as __hibernate_sort_row 13: from 14: product product0_) as query 15: WHERE 16: query.__hibernate_sort_row > @p1 17: ORDER BY If, however, you wanted to bring as well the associated order details, you might be tempted to try this: 1: session.Query<Product>().Fetch(x => x.OrderDetails).Take(5).Skip(5).ToList(); Which, in turn, will produce this SQL: 1: SELECT 2: TOP (@p0) product1_4_0_, 3: order1_3_1_, 4: name4_0_, 5: price4_0_, 6: order2_3_1_, 7: product3_3_1_, 8: quantity3_1_, 9: product3_0__, 10: order1_0__ 11: FROM 12: (select 13: product0_.product_id as product1_4_0_, 14: orderdetai1_.order_detail_id as order1_3_1_, 15: product0_.name as name4_0_, 16: product0_.price as price4_0_, 17: orderdetai1_.order_id as order2_3_1_, 18: orderdetai1_.product_id as product3_3_1_, 19: orderdetai1_.quantity as quantity3_1_, 20: orderdetai1_.product_id as product3_0__, 21: orderdetai1_.order_detail_id as order1_0__, 22: ROW_NUMBER() OVER( 23: ORDER BY 24: CURRENT_TIMESTAMP) as __hibernate_sort_row 25: from 26: product product0_ 27: left outer join 28: order_detail orderdetai1_ 29: on product0_.product_id=orderdetai1_.product_id 30: ) as query 31: WHERE 32: query.__hibernate_sort_row > @p1 33: ORDER BY 34: query.__hibernate_sort_row; However, because of the JOIN, what happens is that, if your products have more than one order details, you will get several records – one per order detail – per product, which means that pagination will be broken. There is an workaround, which forces you to write your LINQ query in another way: 1: session.Query<OrderDetail>().Where(x => session.Query<Product>().Select(y => y.ProductId).Take(5).Skip(5).Contains(x.Product.ProductId)).Select(x => x.Product).ToList() Or, using HQL: 1: session.CreateQuery("select od.Product from OrderDetail od where od.Product.ProductId in (select p.ProductId from Product p skip 5 take 5)").List<Product>(); The generated SQL will then be: 1: select 2: product1_.product_id as product1_4_, 3: product1_.name as name4_, 4: product1_.price as price4_ 5: from 6: order_detail orderdetai0_ 7: left outer join 8: product product1_ 9: on orderdetai0_.product_id=product1_.product_id 10: where 11: orderdetai0_.product_id in ( 12: SELECT 13: TOP (@p0) product_id 14: FROM 15: (select 16: product2_.product_id, 17: ROW_NUMBER() OVER( 18: ORDER BY 19: CURRENT_TIMESTAMP) as __hibernate_sort_row 20: from 21: product product2_) as query 22: WHERE 23: query.__hibernate_sort_row > @p1 24: ORDER BY 25: query.__hibernate_sort_row); Which will get you what you want: for 5 products, all of their order details.

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  • Sound vs. Valid Argument

    - by MarkPearl
    Today I spent some time reviewing my Formal Logic course for my up coming exam. I came across a section that I have never really explored in any proper depth… the difference between a valid argument and a sound argument. Here go some notes I made… What is an argument? In this case we are not referring to a verbal fight, but more what we call a set of premise followed by a conclusion. Before we go further we need to understand what a premise is… a premise is a statement that an argument claims will induce or justify a conclusion. Think of a premise as an assumption that something is true. So, an argument can consist of one or more premises and a conclusion… When is an argument valid? An argument can be either valid or invalid. An argument is valid if, and only if, it is impossible for there to be a situation in which all it's premises are TRUE and it's conclusion is FALSE. It is generally easier to determine if an argument is invalid. Do this by applying the following… Assume that all the premises are true, then ask yourself if it is now possible for the conclusion to be false. If the answer is "yes," the argument is invalid. If it's "no," the argument is valid. Example 1… P1 – Mark is Tall P2 – Mark is a boy C –  Mark is a tall boy Walkthrough 1… Assume Mark is Tall is true and also assume that Mark is a boy. Based on these two premises, the conclusion is also true – Mark is a tall boy, thus the it is a valid argument. Let’s make this an invalid argument…   Example 2… P1 – Mark is Tall P2 – Mark is a boy C – Mark is a short boy Walkthrough 2… This would be an invalid argument, since from the premises we assume that Mark is tall and he is a boy, and then the conclusion goes against this by saying that Mark is short. Thus an invalid argument.   When is an argument sound? An argument is said to be sound when it is valid and all the premises are indeed true (not just assumed to be true). Rephrased, an argument is said to be sound when the conclusion will follow from the premises and the premises are indeed true in real life. In example 1 we were referring to a specific person, if we generalized it a bit we could come up with the following example.   Example 3 P1 – All people called Mark are tall P2 – I know a specific person called Mark C – He is a tall person   In this instance, it is a valid argument (we assume the premises are true, which leads to the conclusion being true), but the argument is NOT sound. In the real world there must be at least one person called Mark who is not tall. Something also to note, all invalid arguments are also unsound – this makes sense, if an argument is not valid, how on earth can it be true in the real world.   What happens when the premises contradict themselves? This is an interesting one… An argument is valid if, and only if, it is impossible for there to be a situation in which all it's premises are TRUE and it's conclusion is FALSE. When premises are contradictory, the argument is always valid because it is impossible for all the premises to be true at one time. Lets look at an example.. P1 - Elvis is dead P2 – Elvis is alive C – Laura is a woolly mammoth This is a valid argument, but not a sound one. Think about it. Is it possible to have a situation in which the premises are true and the conclusion is false? Sure, it's possible to have a situation in which the conclusion is false, but for the argument to be invalid, it has to be possible for the premises to all be true at the same time the conclusion is false. So if the premises can't all be true, the argument is valid. (If you still think the argument is invalid, draw a picture in which the premises are all true and the conclusion is false. Remember, there's only one Elvis, and you can't be both dead and alive.) For more info on this I suggest reading the following blog post.

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  • Denali Paging–Key seek lookups

    - by Dave Ballantyne
    In my previous post “Denali Paging – is it win.win ?” I demonstrated the use of using the Paging functionality within Denali.  On reflection,  I think i may of been a little unfair and should of continued always planned to continue my investigations to the next step. In Pauls article, he uses a combination of ctes to first scan the ordered keys which is then filtered using TOP and rownumber and then uses those keys to seek the data.  So what happens if we replace the scanning portion of the code with the denali paging functionality. Heres the original procedure,  we are going to replace the functionality of the Keys and SelectedKeys ctes : CREATE  PROCEDURE dbo.FetchPageKeySeek         @PageSize   BIGINT,         @PageNumber BIGINT AS BEGIN         -- Key-Seek algorithm         WITH    Keys         AS      (                 -- Step 1 : Number the rows from the non-clustered index                 -- Maximum number of rows = @PageNumber * @PageSize                 SELECT  TOP (@PageNumber * @PageSize)                         rn = ROW_NUMBER() OVER (ORDER BY P1.post_id ASC),                         P1.post_id                 FROM    dbo.Post P1                 ORDER   BY                         P1.post_id ASC                 ),                 SelectedKeys         AS      (                 -- Step 2 : Get the primary keys for the rows on the page we want                 -- Maximum number of rows from this stage = @PageSize                 SELECT  TOP (@PageSize)                         SK.rn,                         SK.post_id                 FROM    Keys SK                 WHERE   SK.rn > ((@PageNumber - 1) * @PageSize)                 ORDER   BY                         SK.post_id ASC                 )         SELECT  -- Step 3 : Retrieve the off-index data                 -- We will only have @PageSize rows by this stage                 SK.rn,                 P2.post_id,                 P2.thread_id,                 P2.member_id,                 P2.create_dt,                 P2.title,                 P2.body         FROM    SelectedKeys SK         JOIN    dbo.Post P2                 ON  P2.post_id = SK.post_id         ORDER   BY                 SK.post_id ASC; END; and here is the replacement procedure using paging: CREATE  PROCEDURE dbo.FetchOffsetPageKeySeek         @PageSize   BIGINT,         @PageNumber BIGINT AS BEGIN         -- Key-Seek algorithm         WITH    SelectedKeys         AS      (                 SELECT  post_id                 FROM    dbo.Post P1                 ORDER   BY post_id ASC                 OFFSET  @PageSize * (@PageNumber-1) ROWS                 FETCH NEXT @PageSize ROWS ONLY                 )         SELECT  P2.post_id,                 P2.thread_id,                 P2.member_id,                 P2.create_dt,                 P2.title,                 P2.body         FROM    SelectedKeys SK         JOIN    dbo.Post P2                 ON  P2.post_id = SK.post_id         ORDER   BY                 SK.post_id ASC; END; Notice how all i have done is replace the functionality with the Keys and SelectedKeys CTEs with the paging functionality. So , what is the comparative performance now ?. Exactly the same amount of IO and memory usage , but its now pretty obvious that in terms of CPU and overall duration we are onto a winner.    

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  • Solaris X86 64-bit Assembly Programming

    - by danx
    Solaris X86 64-bit Assembly Programming This is a simple example on writing, compiling, and debugging Solaris 64-bit x86 assembly language with a C program. This is also referred to as "AMD64" assembly. The term "AMD64" is used in an inclusive sense to refer to all X86 64-bit processors, whether AMD Opteron family or Intel 64 processor family. Both run Solaris x86. I'm keeping this example simple mainly to illustrate how everything comes together—compiler, assembler, linker, and debugger when using assembly language. The example I'm using here is a C program that calls an assembly language program passing a C string. The assembly language program takes the C string and calls printf() with it to print the string. AMD64 Register Usage But first let's review the use of AMD64 registers. AMD64 has several 64-bit registers, some special purpose (such as the stack pointer) and others general purpose. By convention, Solaris follows the AMD64 ABI in register usage, which is the same used by Linux, but different from Microsoft Windows in usage (such as which registers are used to pass parameters). This blog will only discuss conventions for Linux and Solaris. The following chart shows how AMD64 registers are used. The first six parameters to a function are passed through registers. If there's more than six parameters, parameter 7 and above are pushed on the stack before calling the function. The stack is also used to save temporary "stack" variables for use by a function. 64-bit Register Usage %rip Instruction Pointer points to the current instruction %rsp Stack Pointer %rbp Frame Pointer (saved stack pointer pointing to parameters on stack) %rdi Function Parameter 1 %rsi Function Parameter 2 %rdx Function Parameter 3 %rcx Function Parameter 4 %r8 Function Parameter 5 %r9 Function Parameter 6 %rax Function return value %r10, %r11 Temporary registers (need not be saved before used) %rbx, %r12, %r13, %r14, %r15 Temporary registers, but must be saved before use and restored before returning from the current function (usually with the push and pop instructions). 32-, 16-, and 8-bit registers To access the lower 32-, 16-, or 8-bits of a 64-bit register use the following: 64-bit register Least significant 32-bits Least significant 16-bits Least significant 8-bits %rax%eax%ax%al %rbx%ebx%bx%bl %rcx%ecx%cx%cl %rdx%edx%dx%dl %rsi%esi%si%sil %rdi%edi%di%axl %rbp%ebp%bp%bp %rsp%esp%sp%spl %r9%r9d%r9w%r9b %r10%r10d%r10w%r10b %r11%r11d%r11w%r11b %r12%r12d%r12w%r12b %r13%r13d%r13w%r13b %r14%r14d%r14w%r14b %r15%r15d%r15w%r15b %r16%r16d%r16w%r16b There's other registers present, such as the 64-bit %mm registers, 128-bit %xmm registers, 256-bit %ymm registers, and 512-bit %zmm registers. Except for %mm registers, these registers may not present on older AMD64 processors. Assembly Source The following is the source for a C program, helloas1.c, that calls an assembly function, hello_asm(). $ cat helloas1.c extern void hello_asm(char *s); int main(void) { hello_asm("Hello, World!"); } The assembly function called above, hello_asm(), is defined below. $ cat helloas2.s /* * helloas2.s * To build: * cc -m64 -o helloas2-cpp.s -D_ASM -E helloas2.s * cc -m64 -c -o helloas2.o helloas2-cpp.s */ #if defined(lint) || defined(__lint) /* ARGSUSED */ void hello_asm(char *s) { } #else /* lint */ #include <sys/asm_linkage.h> .extern printf ENTRY_NP(hello_asm) // Setup printf parameters on stack mov %rdi, %rsi // P2 (%rsi) is string variable lea .printf_string, %rdi // P1 (%rdi) is printf format string call printf ret SET_SIZE(hello_asm) // Read-only data .text .align 16 .type .printf_string, @object .printf_string: .ascii "The string is: %s.\n\0" #endif /* lint || __lint */ In the assembly source above, the C skeleton code under "#if defined(lint)" is optionally used for lint to check the interfaces with your C program--very useful to catch nasty interface bugs. The "asm_linkage.h" file includes some handy macros useful for assembly, such as ENTRY_NP(), used to define a program entry point, and SET_SIZE(), used to set the function size in the symbol table. The function hello_asm calls C function printf() by passing two parameters, Parameter 1 (P1) is a printf format string, and P2 is a string variable. The function begins by moving %rdi, which contains Parameter 1 (P1) passed hello_asm, to printf()'s P2, %rsi. Then it sets printf's P1, the format string, by loading the address the address of the format string in %rdi, P1. Finally it calls printf. After returning from printf, the hello_asm function returns itself. Larger, more complex assembly functions usually do more setup than the example above. If a function is returning a value, it would set %rax to the return value. Also, it's typical for a function to save the %rbp and %rsp registers of the calling function and to restore these registers before returning. %rsp contains the stack pointer and %rbp contains the frame pointer. Here is the typical function setup and return sequence for a function: ENTRY_NP(sample_assembly_function) push %rbp // save frame pointer on stack mov %rsp, %rbp // save stack pointer in frame pointer xor %rax, %r4ax // set function return value to 0. mov %rbp, %rsp // restore stack pointer pop %rbp // restore frame pointer ret // return to calling function SET_SIZE(sample_assembly_function) Compiling and Running Assembly Use the Solaris cc command to compile both C and assembly source, and to pre-process assembly source. You can also use GNU gcc instead of cc to compile, if you prefer. The "-m64" option tells the compiler to compile in 64-bit address mode (instead of 32-bit). $ cc -m64 -o helloas2-cpp.s -D_ASM -E helloas2.s $ cc -m64 -c -o helloas2.o helloas2-cpp.s $ cc -m64 -c helloas1.c $ cc -m64 -o hello-asm helloas1.o helloas2.o $ file hello-asm helloas1.o helloas2.o hello-asm: ELF 64-bit LSB executable AMD64 Version 1 [SSE FXSR FPU], dynamically linked, not stripped helloas1.o: ELF 64-bit LSB relocatable AMD64 Version 1 helloas2.o: ELF 64-bit LSB relocatable AMD64 Version 1 $ hello-asm The string is: Hello, World!. Debugging Assembly with MDB MDB is the Solaris system debugger. It can also be used to debug user programs, including assembly and C. The following example runs the above program, hello-asm, under control of the debugger. In the example below I load the program, set a breakpoint at the assembly function hello_asm, display the registers and the first parameter, step through the assembly function, and continue execution. $ mdb hello-asm # Start the debugger > hello_asm:b # Set a breakpoint > ::run # Run the program under the debugger mdb: stop at hello_asm mdb: target stopped at: hello_asm: movq %rdi,%rsi > $C # display function stack ffff80ffbffff6e0 hello_asm() ffff80ffbffff6f0 0x400adc() > $r # display registers %rax = 0x0000000000000000 %r8 = 0x0000000000000000 %rbx = 0xffff80ffbf7f8e70 %r9 = 0x0000000000000000 %rcx = 0x0000000000000000 %r10 = 0x0000000000000000 %rdx = 0xffff80ffbffff718 %r11 = 0xffff80ffbf537db8 %rsi = 0xffff80ffbffff708 %r12 = 0x0000000000000000 %rdi = 0x0000000000400cf8 %r13 = 0x0000000000000000 %r14 = 0x0000000000000000 %r15 = 0x0000000000000000 %cs = 0x0053 %fs = 0x0000 %gs = 0x0000 %ds = 0x0000 %es = 0x0000 %ss = 0x004b %rip = 0x0000000000400c70 hello_asm %rbp = 0xffff80ffbffff6e0 %rsp = 0xffff80ffbffff6c8 %rflags = 0x00000282 id=0 vip=0 vif=0 ac=0 vm=0 rf=0 nt=0 iopl=0x0 status=<of,df,IF,tf,SF,zf,af,pf,cf> %gsbase = 0x0000000000000000 %fsbase = 0xffff80ffbf782a40 %trapno = 0x3 %err = 0x0 > ::dis # disassemble the current instructions hello_asm: movq %rdi,%rsi hello_asm+3: leaq 0x400c90,%rdi hello_asm+0xb: call -0x220 <PLT:printf> hello_asm+0x10: ret 0x400c81: nop 0x400c85: nop 0x400c88: nop 0x400c8c: nop 0x400c90: pushq %rsp 0x400c91: pushq $0x74732065 0x400c96: jb +0x69 <0x400d01> > 0x0000000000400cf8/S # %rdi contains Parameter 1 0x400cf8: Hello, World! > [ # Step and execute 1 instruction mdb: target stopped at: hello_asm+3: leaq 0x400c90,%rdi > [ mdb: target stopped at: hello_asm+0xb: call -0x220 <PLT:printf> > [ The string is: Hello, World!. mdb: target stopped at: hello_asm+0x10: ret > [ mdb: target stopped at: main+0x19: movl $0x0,-0x4(%rbp) > :c # continue program execution mdb: target has terminated > $q # quit the MDB debugger $ In the example above, at the start of function hello_asm(), I display the stack contents with "$C", display the registers contents with "$r", then disassemble the current function with "::dis". The first function parameter, which is a C string, is passed by reference with the string address in %rdi (see the register usage chart above). The address is 0x400cf8, so I print the value of the string with the "/S" MDB command: "0x0000000000400cf8/S". I can also print the contents at an address in several other formats. Here's a few popular formats. For more, see the mdb(1) man page for details. address/S C string address/C ASCII character (1 byte) address/E unsigned decimal (8 bytes) address/U unsigned decimal (4 bytes) address/D signed decimal (4 bytes) address/J hexadecimal (8 bytes) address/X hexadecimal (4 bytes) address/B hexadecimal (1 bytes) address/K pointer in hexadecimal (4 or 8 bytes) address/I disassembled instruction Finally, I step through each machine instruction with the "[" command, which steps over functions. If I wanted to enter a function, I would use the "]" command. Then I continue program execution with ":c", which continues until the program terminates. MDB Basic Cheat Sheet Here's a brief cheat sheet of some of the more common MDB commands useful for assembly debugging. There's an entire set of macros and more powerful commands, especially some for debugging the Solaris kernel, but that's beyond the scope of this example. $C Display function stack with pointers $c Display function stack $e Display external function names $v Display non-zero variables and registers $r Display registers ::fpregs Display floating point (or "media" registers). Includes %st, %xmm, and %ymm registers. ::status Display program status ::run Run the program (followed by optional command line parameters) $q Quit the debugger address:b Set a breakpoint address:d Delete a breakpoint $b Display breakpoints :c Continue program execution after a breakpoint [ Step 1 instruction, but step over function calls ] Step 1 instruction address::dis Disassemble instructions at an address ::events Display events Further Information "Assembly Language Techniques for Oracle Solaris on x86 Platforms" by Paul Lowik (2004). Good tutorial on Solaris x86 optimization with assembly. The Solaris Operating System on x86 Platforms An excellent, detailed tutorial on X86 architecture, with Solaris specifics. By an ex-Sun employee, Frank Hofmann (2005). "AMD64 ABI Features", Solaris 64-bit Developer's Guide contains rules on data types and register usage for Intel 64/AMD64-class processors. (available at docs.oracle.com) Solaris X86 Assembly Language Reference Manual (available at docs.oracle.com) SPARC Assembly Language Reference Manual (available at docs.oracle.com) System V Application Binary Interface (2003) defines the AMD64 ABI for UNIX-class operating systems, including Solaris, Linux, and BSD. Google for it—the original website is gone. cc(1), gcc(1), and mdb(1) man pages.

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  • Operating systems theory -- using minimum number of semaphores

    - by stackuser
    This situation is prone to deadlock of processes in an operating system and I'd like to solve it with the minimum of semaphores. Basically there are three cooperating processes that all read data from the same input device. Each process, when it gets the input device, must read two consecutive data. I want to use mutual exclusion to do this. Semaphores should be used to synchronize: P1: P2: P3: input(a1,a2) input (b1,b2) input(c1,c2) Y=a1+c1 W=b2+c2 Z=a2+b1 Print (X) X=Z-Y+W The declaration and initialization that I think would work here are: semaphore s=1 sa1 = 0, sa2 = 0, sb1 = 0, sb2 = 0, sc1 = 0, sc2 = 0 I'm sure that any kernel programmers that happen on this can knock this out in a minute or 2. Diagram of cooperating Processes and one input device: It seems like P1 and P2 would start something like: wait(s) input (a1/b1, a2/b2) signal(s)

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  • DBCC MEMUSAGE in 2005/8 ?

    - by steveh99999
    I used to like using undocumented command DBCC MEMUSAGE in SQL 2000 to see which tables were using space in SQL data cache. In SQL 2005, this command is not longer present. Instead a DMV – sys.dm_os_buffer_descriptors – can be used to display data cache contents,  but this doesn’t quite give you the same output as DBCC MEMUSAGE. I’m also aware that you can use Quest’s spotlight tool to view a summary of data cache contents. Using  this post by Umachandar Jayachandran  of Microsoft, I was able to create the following equivalent for SQL 2005/8. I’ve wrapped Umachandar’s original query in a CTE to produce summary information :- ;WITH memusage_CTE AS (SELECT bd.database_id, bd.file_id, bd.page_id, bd.page_type , COALESCE(p1.object_id, p2.object_id) AS object_id , COALESCE(p1.index_id, p2.index_id) AS index_id , bd.row_count, bd.free_space_in_bytes, CONVERT(TINYINT,bd.is_modified) AS 'DirtyPage' FROM sys.dm_os_buffer_descriptors AS bd JOIN sys.allocation_units AS au ON au.allocation_unit_id = bd.allocation_unit_id OUTER APPLY ( SELECT TOP(1) p.object_id, p.index_id FROM sys.partitions AS p WHERE p.hobt_id = au.container_id AND au.type IN (1, 3) ) AS p1 OUTER APPLY ( SELECT TOP(1) p.object_id, p.index_id FROM sys.partitions AS p WHERE p.partition_id = au.container_id AND au.type = 2 ) AS p2 WHERE  bd.database_id = DB_ID() AND bd.page_type IN ('DATA_PAGE', 'INDEX_PAGE') ) SELECT TOP 20 DB_NAME(database_id) AS 'Database',OBJECT_NAME(object_id,database_id) AS 'Table Name', index_id,COUNT(*) AS 'Pages in Cache', SUM(dirtyPage) AS 'Dirty Pages' FROM memusage_CTE GROUP BY database_id, object_id, index_id ORDER BY COUNT(*) DESC I’m not 100% happy with the results of the above query however… I’ve noticed that on a busy BizTalk messageBox database  it will return information on pages that contain GHOST rows – . ie where data has already been deleted but has yet to be cleaned-up by a background process – I’m need to investigate further why cache on this server apparently contains so much GHOST data… For more information on the background ghost cleanup process, see this article by Paul Randall. However, I think the results of this query should still be of interest to a DBA. I have another post to come shortly regarding an example I encountered where this information proved useful to me… I notice in SQL 2008, sys.dm_os_buffer_descriptors gained an extra column – numa_mode – I’m interested to see how this is populated and how useful this column can be on a NUMA-enabled system. I’m assuming in theory you could use this column to help analyse how your tables are spread across Numa-enabled data-cache ?

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  • Operating systems -- using minimum number of semaphores

    - by stackuser
    The three cooperating processes all read data from the same input device. Each process, when it gets the input device, must read two consecutive data. I want to use mutual exclusion to do this. The declaration and initialization that I think would work here are: semaphore s=1 sa1 = 0, sa2 = 0, sb1 = 0, sb2 = 0, sc1 = 0, sc2 = 0 I'd like to use semaphores to synchronize the following processes: P1: P2: P3: input(a1,a2) input (b1,b2) input(c1,c2) Y=a1+c1 W=b2+c2 Z=a2+b1 Print (X) X=Z-Y+W I'm wondering how to use the minimum number of semaphores to solve this. Diagram of cooperating Processes and one input device: It seems like P1 and P2 would start something like: wait(s) input (a1/b1, a2/b2) signal(s)

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  • designing classes with similar goal but widely different decisional core

    - by Stefano Borini
    I am puzzled on how to model this situation. Suppose you have an algorithm operating in a loop. At every loop, a procedure P must take place, whose role is to modify an input data I into an output data O, such that O = P(I). In reality, there are different flavors of P, say P1, P2, P3 and so on. The choice of which P to run is user dependent, but all P have the same finality, produce O from I. This called well for a base class PBase with a method PBase::apply, with specific reimplementations of P1::apply(I), P2::apply(I), and P3::apply(I). The actual P class gets instantiated in a factory method, and the loop stays simple. Now, I have a case of P4 which follows the same principle, but this time needs additional data from the loop (such as the current iteration, and the average value of O during the previous iterations). How would you redesign for this case?

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  • Nautilus build fail

    - by ts01
    I am trying to patch Nautilus 3.2.1 on 11.10 with this patch (dual screen fix). So I've executed whole sequence: sudo apt-get install devscripts sudo apt-get build-dep nautilus apt-get source nautilus cd nautilus-3.2.1/ cp ~/nautilus.patch . patch --dry-run -p1 < nautilus.patch patch -p1 < nautilus.patch debuild And I've got finally fatal error (whole output here): dpkg-buildpackage: error: dpkg-source -b nautilus-3.2.1 gave error exit status 13 debuild: fatal error at line 1348: dpkg-buildpackage -rfakeroot -D -us -uc failed Any ideas?

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  • Why is bzip2 needed in the kernel patch instructions?

    - by user12657
    This was from here. Extract the patch tar -xvzf /usr/src/web100-2.5.22-200810130047.tar.gz bzip2 web100/ web100-2.6.27-2.5.22-200810130047.patch Test the patch bzip2 -dc /usr/src/linux/web100/ web100-2.6.27-2.5.22-200810130047.patch.bz2 | patch -p1 --dry-run I looked at the .patch, the diff output of many files and the file .patch.bz2 after the bzip2 command which is too also the diff output of many files, they seem to be the same. My question is why is bzip2 even needed to turn the .patch into a .patch.bz2? Is it for the redirection to std output from the -dc option for the patch command? Even if it is, why not just not just use the patch command in the form something like this:patch -p1 < patchfile? I don't see why the bzip2 is done here. Also, I think the bzip2 might have an extra space in the command after web100/, right?

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  • What causes Multi-Page allocations?

    - by SQLOS Team
    Writing about changes in the Denali Memory Manager In his last post Rusi mentioned: " In previous SQL versions only the 8k allocations were limited by the ‘max server memory’ configuration option.  Allocations larger than 8k weren’t constrained." In SQL Server versions before Denali single page allocations and multi-Page allocations are handled by different components, the Single Page Allocator (which is responsible for Buffer Pool allocations and governed by 'max server memory') and the Multi-Page allocator (MPA) which handles allocations of greater than an 8K page. If there are many multi-page allocations this can affect how much memory needs to be reserved outside 'max server memory' which may in turn involve setting the -g memory_to_reserve startup parameter. We'll follow up with more generic articles on the new Memory Manager structure, but in this post I want to clarify what might cause these larger allocations. So what kinds of query result in MPA activity? I was asked this question the other day after delivering an MCM webcast on Memory Manager changes in Denali. After asking around our Dev team I was connected to one of our test leads Sangeetha who had tested the plan cache, and kindly provided this example of an MPA intensive query: A workload that has stored procedures with a large # of parameters (say > 100, > 500), and then invoked via large ad hoc batches, where each SP has different parameters will result in a plan being cached for this “exec proc” batch. This plan will result in MPA.   Exec proc_name @p1, ….@p500 Exec proc_name @p1, ….@p500 . . . Exec proc_name @p1, ….@p500 Go   Another workload would be large adhoc batches of the form: Select * from t where col1 in (1, 2, 3, ….500) Select * from t where col1 in (1, 2, 3, ….500) Select * from t where col1 in (1, 2, 3, ….500) … Go  In Denali all page allocations are handled by an "Any size page allocator" and included in 'max server memory'. The buffer pool effectively becomes a client of the any size page allocator, which in turn relies on the memory manager. - Guy Originally posted at http://blogs.msdn.com/b/sqlosteam/

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  • How to manually detect deadlocks

    - by Dawson
    I understand the concepts of deadlock well enough, but when I'm given a problem like the one below I'm not sure how to go about solving it. I can draw a resource allocation graph, but I'm not sure how to solve it from there. Is there a better more formal way of solving this? Consider a system with five processes, P1 through P5, and five resources, R1 through R5. Resource ownership is as follows. • P1 holds R1 and wants R3 • P2 holds R2 and wants R1 • P3 holds R3 and wants R5 • P4 holds R5 and wants R2 • P5 holds R4 and wants R2 Is this system deadlocked? Justify your answer. If the system is deadlocked, list the involved processes.

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  • Get all triangles that are < N dist from you?

    - by CyanPrime
    Does anyone know of a way I could add a radius to this code for p? Like basically saying "this is true if the triangle is < N dist from the point" public boolean isPointInTriangle( Vector3f p, Vector3f a, Vector3f b, Vector3f c ) { return ( pointsAreOnSameSide(p, a, b, c) && pointsAreOnSameSide(p, b, a, c) && pointsAreOnSameSide(p, c, a, b) ); } public boolean pointsAreOnSameSide( Vector3f p1, Vector3f p2, Vector3f a, Vector3f b ) { Vector3f diffba = new Vector3f(0,0,0); Vector3f.sub( b, a, diffba ); Vector3f diffp1a = new Vector3f(0,0,0); Vector3f.sub( p1, a, diffp1a ); Vector3f diffp2a = new Vector3f(0,0,0); Vector3f.sub( p2, a, diffp2a ); Vector3f cross1 = Vector3f.cross(diffba, diffp1a); Vector3f cross2 = Vector3f.cross(diffba, diffp2a); return ( Vector3f.dot( cross1, cross2 ) >= 0 ); }

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  • Basic Android game loop having issues

    - by WillDaBeast509
    I've set up a very basic game loop that should draw a circle, run 100 times, then draw another. I also have a text field that should display how many times the loop has ran. However, the screen seems to not update. It displays a different value for the tick count (different each time the app is ran) and simply stays there. After exiting the app, I get an error saying "Unfortunately, MyApp has stopped." Here is the relevant code: DrawView public class DrawView extends SurfaceView implements SurfaceHolder.Callback { Paint p = new Paint(); MainThread thread; private int y=0; public DrawView(Context c) { super(c); thread = new MainThread(this, getHolder()); thread.running = true; getHolder().addCallback(this); setFocusable(true); } public void draw(Canvas c) { if(c==null) return; //super.onDraw(c); c.drawColor(Color.WHITE); p.setColor(Color.RED); p.setTextSize(32); p.setTypeface(Typeface.SANS_SERIF); c.drawCircle(getWidth()/2-100,getHeight()/2, 50, p); c.drawText("y = " + y, 50, 50, p); if(y>=100) { Log.i("DRAW", "drawing circle"); c.drawCircle(getWidth()/2+100,getHeight()/2, 50, p); } else y++; Log.i("INFO", "y = " + y); } @Override public boolean onTouchEvent(MotionEvent event) { return true; } public void onDraw(Canvas c){} public void surfaceCreated(SurfaceHolder p1) { thread.start(); } public void surfaceChanged(SurfaceHolder p1, int p2, int p3, int p4) { // TODO: Implement this method } public void surfaceDestroyed(SurfaceHolder p1) { thread.running = false; boolean retry = true; while (retry) { try { thread.join(); retry = false; } catch (InterruptedException e) { Log.i("EX", "cathing exception"); } } } } MainThread public class MainThread extends Thread { private DrawView page; private SurfaceHolder holder; public boolean running; public MainThread(DrawView p, SurfaceHolder h) { super(); page = p; holder = h; } @Override public void run() { while(running) { Canvas c = holder.lockCanvas(); page.draw(c); holder.unlockCanvasAndPost(c); } } } Here is an example log outupt: http://pastebin.com/tM9dUPuk It counts the number of ticks correctly and should draw the second circle, but the screen looks like its not updating. After closing the app, the log continues to run and keep outputting "y = 100 drawing circle" until it crashes and shows the error report. What is going on and how can I fix these two problems?

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  • new and delete operator overloading

    - by Angus
    I am writing a simple program to understand the new and delete operator overloading. How is the size parameter passed into the new operator? For reference, here is my code: #include<iostream> #include<stdlib.h> #include<malloc.h> using namespace std; class loc{ private: int longitude,latitude; public: loc(){ longitude = latitude = 0; } loc(int lg,int lt){ longitude -= lg; latitude -= lt; } void show(){ cout << "longitude" << endl; cout << "latitude" << endl; } void* operator new(size_t size); void operator delete(void* p); void* operator new[](size_t size); void operator delete[](void* p); }; void* loc :: operator new(size_t size){ void* p; cout << "In overloaded new" << endl; p = malloc(size); cout << "size :" << size << endl; if(!p){ bad_alloc ba; throw ba; } return p; } void loc :: operator delete(void* p){ cout << "In delete operator" << endl; free(p); } void* loc :: operator new[](size_t size){ void* p; cout << "In overloaded new[]" << endl; p = malloc(size); cout << "size :" << size << endl; if(!p){ bad_alloc ba; throw ba; } return p; } void loc :: operator delete[](void* p){ cout << "In delete operator - array" << endl; free(p); } int main(){ loc *p1,*p2; int i; cout << "sizeof(loc)" << sizeof(loc) << endl; try{ p1 = new loc(10,20); } catch (bad_alloc ba){ cout << "Allocation error for p1" << endl; return 1; } try{ p2 = new loc[10]; } catch(bad_alloc ba){ cout << "Allocation error for p2" << endl; return 1; } p1->show(); for(i = 0;i < 10;i++){ p2[i].show(); } delete p1; delete[] p2; return 0; }

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  • -Java- Swing GUI - Moving around components specifically with layouts

    - by Xemiru Scarlet Sanzenin
    I'm making a little test GUI for something I'm making. However, problems occur with the positioning of the panels. public winInit() { super("Chatterbox - Login"); try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch(ClassNotFoundException e) { } catch (InstantiationException e) { } catch (IllegalAccessException e) { } catch (UnsupportedLookAndFeelException e) { } setSize(300,135); pn1 = new JPanel(); pn2 = new JPanel(); pn3 = new JPanel(); l1 = new JLabel("Username"); l2 = new JLabel("Password"); l3 = new JLabel("Random text here"); l4 = new JLabel("Server Address"); l5 = new JLabel("No address set."); i1 = new JTextField(10); p1 = new JPasswordField(10); b1 = new JButton("Connect"); b2 = new JButton("Register"); b3 = new JButton("Set IP"); l4.setBounds(10, 12, getDim(l4).width, getDim(l4).height); l1.setBounds(10, 35, getDim(l1).width, getDim(l1).height); l2.setBounds(10, 60, getDim(l2).width, getDim(l2).height); l3.setBounds(10, 85, getDim(l3).width, getDim(l3).height); l5.setBounds(l4.getBounds().width + 14, 12, l5.getPreferredSize().width, l5.getPreferredSize().height); l5.setForeground(Color.gray); i1.setBounds(getDim(l1).width + 15, 35, getDim(i1).width, getDim(i1).height); p1.setBounds(getDim(l1).width + 15, 60, getDim(p1).width, getDim(p1).height); b1.setBounds(getDim(l1).width + getDim(i1).width + 23, 34, getDim(b2).width, getDim(b1).height - 5); b2.setBounds(getDim(l1).width + getDim(i1).width + 23, 60, getDim(b2).width, getDim(b2).height - 5); b3.setBounds(getDim(l1).width + getDim(i1).width + 23, 10, etDim(b2).width, getDim(b3).height - 5); b1.addActionListener(clickButton); b2.addActionListener(clickButton); b3.addActionListener(clickButton); pn1.setLayout(new FlowLayout(FlowLayout.RIGHT)); pn2.setLayout(new FlowLayout(FlowLayout.RIGHT)); pn1.add(l1); pn1.add(i1); pn1.add(b1); pn2.add(l2); pn2.add(p1); pn2.add(b2); add(pn1); add(pn2); } I am attempting to use FlowLayout to position the panels in the way desired. I'd use BorderLayout while adding, but the vertical spacing is too far away when I just use directions closest to one another. The output of this code is to create a window, 300,150, place whatever's in the two panels in the exact same spaces. Yes, I realize there's useless code there with setBounds(), but that was just me screwing around with Absolute Positioning, which wasn't working out for me either.

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  • route propogation using OSPF in a network

    - by liv2hak
    I am using Juniper J-series routers to emulate a small telco and VPN customer.The internal routing will be configured with OSPF,MPLS including a default and backup path,RSVP for distributing labels withing the telco,OSPF for distributing routes from the customer edge (CE) routers to the VRF's in the adjacent PE's and finally iBGP for distributing customer routes between VRF's in different PEs. The topology of the network is shown below. The Addressing scheme for the network is as follows. UOW-TAU ******* ge-0/0/0 192.168.3.1 TAU-PE1 ******* ge-0/0/0 10.0.1.0 ge-0/0/1 10.0.2.0 ge-0/0/2 192.168.3.2 TAU-P1 ****** ge-0/0/0 172.16.1.0 ge-0/0/1 172.16.3.1 ge-0/0/2 10.0.2.2 HAM-P1 ****** ge-0/0/0 172.16.3.2 ge-0/0/1 172.16.2.1 ge-0/0/3 10.0.3.2 ACK-P1 ****** ge-0/0/0 172.16.1.2 ge-0/0/2 172.16.2.2 ge-0/0/3 10.0.1.2 HAM-PE1 ******* ge-0/0/0 10.0.3.1 ge-0/0/2 192.168.4.2 UOW-HAM ******* ge-0/0/0 192.168.4.1 I also set up loopback address for each node. I want to setup OSPF so that path to each internal subnet and router loopback address is propogated to all PE and P nodes.I also want to select a single area for PE and P nodes,and on each node I should add each interface that should be propogated. How do I accomplish this.? With my understanding below is the procedure to achieve this.Is the below explanation correct? I set up OSPF on UOW-TAU ge-0/0/0 interface and ge-0/0/1 interface and UOW-HAM ge-0/0/0 interface and ge-0/0/1 interface. let me call this Area 100. Once I have done this I should be able to reach each node from others using ping and traceroute. Any help is highly appreciated.

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  • Change source address based on destination IP

    - by hgj
    We have several "router" machines that gather a lot of external IP addresses on the same host and redirect, NAT or proxy the traffic to the internal network. They also act as routers for the machines on the internal network. This works fine, however I am unable to make the routing table, so I can change the source address, based on the destination a machine from the internal network want to access. Let's say I have a router, that has public addresses P1 (5.5.5.1/24) and P2 (5.5.5.2/24). All traffic goes through P1, but if necessary, the host is reachable on P2 too. This looks like this and works fine: > ip addr ... 1: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether aa:bb:cc:dd:ee:11 brd ff:ff:ff:ff:ff:ff inet 5.5.5.1/24 brd 5.5.5.255 scope global eth1 inet 5.5.5.2/24 brd 5.5.5.255 scope global secondary eth1:p2 ... Now I want to use P2 as the source address, if I want to access the Google DNS service for example (8.8.8.8). So I add a row in the routing table like: > ip route add 8.8.8.8 via 5.5.5.254 dev eth1 src 5.5.5.2 > ip route ... default via 5.5.5.254 dev eth1 5.5.5.0/24 dev eth1 proto kernel scope link src 5.5.5.1 8.8.8.8 via 5.5.5.254 dev eth1 src 5.5.5.2 ... But this does not work. If I ping 8.8.8.8, the host still uses P1 as the source address, and does not use P2 at all for outgoing connections. Am I doing it right? I guess not...

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  • Mysql: Working With 192 Trillion Records... (Yes, 192 Trillion)

    - by Sarah
    Here's the question... Considering 192 trillion records, what should my considerations be? My main concern is speed. Here's the table... CREATE TABLE `ref` ( `id` INTEGER(13) AUTO_INCREMENT DEFAULT NOT NULL, `rel_id` INTEGER(13) NOT NULL, `p1` INTEGER(13) NOT NULL, `p2` INTEGER(13) DEFAULT NULL, `p3` INTEGER(13) DEFAULT NULL, `s` INTEGER(13) NOT NULL, `p4` INTEGER(13) DEFAULT NULL, `p5` INTEGER(13) DEFAULT NULL, `p6` INTEGER(13) DEFAULT NULL, PRIMARY KEY (`id`), KEY (`s`), KEY (`rel_id`), KEY (`p3`), KEY (`p4`) ); Here's the queries... SELECT id, s FROM ref WHERE red_id="$rel_id" AND p3="$p3" AND p4="$p4" SELECT rel_id, p1, p2, p3, p4, p5, p6 FROM ref WHERE id="$id" INSERT INTO rel (rel_id, p1, p2, p3, s, p4, p5, p6) VALUES ("$rel_id", "$p1", "$p2", "$p3", "$s", "$p4", "$p5", "$p6") Here's some notes... The SELECT's will be done much more frequently than the INSERT. However, occasionally I want to add a few hundred records at a time. Load-wise, there will be nothing for hours then maybe a few thousand queries all at once. Don't think I can normalize any more (need the p values in a combination) The database as a whole is very relational. This will be the largest table by far (next largest is about 900k) UPDATE (08/11/2010) Interestingly, I've been given a second option... Instead of 192 trillion I could store 2.6*10^16 (15 zeros, meaning 26 Quadrillion)... But in this second option I would only need to store one bigint(18) as the index in a table. That's it - just the one column. So I would just be checking for the existence of a value. Occasionally adding records, never deleting them. So that makes me think there must be a better solution then mysql for simply storing numbers... Given this second option, should I take it or stick with the first... [edit] Just got news of some testing that's been done - 100 million rows with this setup returns the query in 0.0004 seconds [/edit]

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  • Why SetUnhandledExceptionFilter cannot capture some exception but AddVectoredExceptionHandler can do

    - by wrongite
    I have experienced a problem that the function I passed to the SetUnhandledExceptionFilter didn't get called when the exception code c0000374 raising. But it works fine with the exception code c0000005. Then I tried to use the AddVectoredExceptionHandler instead, and it didn't have the problem, the handler function get called correctly. Is it the API bug? Can I use AddVectoredExceptionHandler instead of SetUnhandledExceptionFilter everywhere? The both functions work correctly with // Exception code c0000005 int* p1 = NULL; *p1 = 99; Only AddVectoredExceptionHandler can capture this exception. // Exception code c0000374 int* p2 = new int; delete p2; delete p2; Test program. #include <tchar.h> #include <fstream> #include <Windows.h> LONG WINAPI VectoredExceptionHandler(PEXCEPTION_POINTERS pExceptionInfo) { std::ofstream f; f.open("VectoredExceptionHandler.txt", std::ios::out | std::ios::trunc); f << std::hex << pExceptionInfo->ExceptionRecord->ExceptionCode << std::endl; f.close(); return EXCEPTION_CONTINUE_SEARCH; } LONG WINAPI TopLevelExceptionHandler(PEXCEPTION_POINTERS pExceptionInfo) { std::ofstream f; f.open("TopLevelExceptionHandler.txt", std::ios::out | std::ios::trunc); f << std::hex << pExceptionInfo->ExceptionRecord->ExceptionCode << std::endl; f.close(); return EXCEPTION_CONTINUE_SEARCH; } int _tmain(int argc, _TCHAR* argv[]) { AddVectoredExceptionHandler(1, VectoredExceptionHandler); SetUnhandledExceptionFilter(TopLevelExceptionHandler); // Exception code c0000374 int* p2 = new int; delete p2; delete p2; // Exception code c0000005 int* p1 = NULL; *p1 = 99; return 0; }

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  • Creating custom URI scheme using URI class

    - by Sorantis
    I need to create a custom URI scheme for my project. i.e urn:myprotocol:{p1}:{p2}:{p3}:{p4} - opaque representation myprotocol://{p1}/{p2}/{p3}/{p4} - hierarchical representation. How can I add my scheme to Java URI class? Or, how can I make Java URI to understand my scheme, so I could use it in my code? Concrete examples are welcome. Thanks.

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  • Beginner SEO question on urlrewrite rules

    - by Charlie
    I just starting reading about SEO and realized that I should change my "GET" queries to / separated keywords for SEO purposes. Here's my question: I have a multi-select checkbox on my form, so my query string would be: http://www.domainname.com/searchitem.html?cat[]=A&cat[]=B&cat[]=C&param1=p1&param2=p2 Whats the convention for handling this kind of queries? changing it to search/catA/catB/catC/p1/p2 doesn't seem right to me but i don't know what else to do Thanks

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  • Using native MySQL driver in Erlang

    - by Mickey Shine
    I am using native MySQL driver (http://code.google.com/p/erlang-mysql-driver/) with mochiweb. When I tried that MySQL driver in shell mode, all woked fine. But when I write some code with Mochiweb, it reported me the following error: =CRASH REPORT==== 4-Jul-2009::04:44:29 === crasher: initial call: mochiweb_socket_server:acceptor_loop/1 pid: <0.61.0> registered_name: [] exception error: no function clause matching mysql:fetch(p1,<<"SELECT * FROM cdb_forums LIMIT 10">>) in function perly_web:loop/2 in call from mochiweb_http:headers/5 ancestors: [perly_web,perly_sup,<0.58.0>] messages: [] links: [<0.60.0>,#Port<0.965>] dictionary: [{mochiweb_request_body,undefined}, {mochiweb_request_qs,[]}, {mochiweb_request_post,[]}, {mochiweb_request_path,"/online"}, {mochiweb_request_cookie, [{"04c_sid","hG9Oyv"}, {"04c_visitedfid","2"}, {"kQx_cookietime","2592000"}, {"kQx_loginuser","admin"}, {"kQx_activationauth", "98b3mdX86fKT9dI4WyKuL61Tqxk%2BW1r6ACpHp9y8itH2xQ"}, {"smile","1D1"}]}] trap_exit: false status: running heap_size: 1597 stack_size: 24 reductions: 5188 neighbours: The code I write in Mochiweb is start(Options) -> {DocRoot, Options1} = get_option(docroot, Options), Loop = fun (Req) -> ?MODULE:loop(Req, DocRoot) end, % we’ll set our maximum to 1 million connections. (default: 2048) mochiweb_http:start([{max, 1000000}, {name, ?MODULE}, {loop, Loop} | Options1]), mysql:start_link(p1, "10.0.0.123", "root", "root", "test"). stop() -> mochiweb_http:stop(?MODULE). loop(Req, DocRoot) -> "/" ++ Path = Req:get(path), case Req:get(method) of Method when Method =:= 'GET'; Method =:= 'HEAD' -> case Path of "online" -> Result1 = mysql:fetch(p1, <<"SELECT * FROM cdb_forums LIMIT 10">>), Body1 = io:format("Result1: ~p~n", [Result1]), Req:ok({"text/plain", Body1}); The connection looks good but when I added Result1 = mysql:fetch(p1, <<"SELECT * FROM cdb_forums LIMIT 10">>), it crashed. Can someone help me? Thanks in advance~ //================================================== updated: I noticed the follwoing information. If that is correct? =PROGRESS REPORT==== 4-Jul-2009::05:49:32 === supervisor: {local,kernel_safe_sup} started: [{pid,<0.65.0>}, {name,inet_gethost_native_sup}, {mfa,{inet_gethost_native,start_link,[]}}, {restart_type,temporary}, {shutdown,1000}, {child_type,worker}] mysql_conn: greeting version "5.1.33-log" (protocol 10) salt "ne0_m'vA" caps 63487 serverchar <<8,2,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0>> salt2 "!|o;vabJ*4bt" mysql_auth send packet 1: <<5,162,0,0,64,66,15,0,8,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,114,111,111,116,0,20,52,235,78, 173,36,251,201,242,172,139,113,231,253,181,245,3, 91,198,111,135>> Link: {ok,<0.62.0>} =SUPERVISOR REPORT==== 4-Jul-2009::05:49:32 === Supervisor: {local,perly_sup} Context: start_error Reason: ok Offender: [{pid,undefined}, {name,perly_web}, {mfa, {perly_web,start, [[{ip,"0.0.0.0"}, {port,8000}, {docroot, "/work/mochiweb-read-only/scripts/perly/priv/www"}]]}}, {restart_type,permanent}, {shutdown,5000}, {child_type,worker}]

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