PGI Support FAQWhat can I do about precision problems The x. This may cause problems when porting code to the x. The increased precision of the x. Also, the increased precision of the x. Examples of problem cases. C. EQ. ONE. LT LT 1. A ALBETA. C DLAMC3 A, ONE. C DLAMC3 C, A. To reduce the precision, the compilers options pc 6. The Kieee switch may be used to disable propagating floating point values and to round the argument values passed to intrinsics sin, cos, etc. Sample report Custom viewsfilters Servers list, organized in groups Integration with EventID. Net Consolidated view for all logs Free for subscribers. How to Reindex Vault on Windows. How to resolve COM Activation failed errors in web applications MapXtreme. NET. 000001576 How to. When I try to install a software using Ubuntu Software center I get Failed to download repository information Check Your Internet connection When I try to do a apt. How come we get different answers on one platform versus a Linux x. The x. 86 architecture implements a floating point stack by using 8 8. Each register uses bits 0 6. This extended 8. 0 bit real format used by floating instructions is the default. When values are loaded into the floating point stack they are automatically converted into the extended real format. The precision of the floating point stack can be controlled, however, by setting the precision control bits bits 8 and 9 of the floating control word appropriately. In this way, the programmer can explicitly set the precision to standard IEEE double or single precision the Intel documentation, however, claims that this only affects the operations of add, subtract, multiply, divide, and square root. We have also noticed that, although extended precision is supposedly the default which is set for the control word, it is set at double precision in the x. Linux systems. Thus, we now also have a pc lt val option which can be used on the command line. IMG/U0079901.PNG' alt='Check The Lmgrd Log File Or Try Lmreread' title='Check The Lmgrd Log File Or Try Lmreread' />The values of lt val are. At first glance, an extra 1. However, operations that are performed exclusively on the floating point stack, without storing into or loading from memory, can cause problems with accumulated values within those 1. This can lead to answers, when rounded, that do not match expected results. We briefly look at several examples which have been encountered. Version 3. 0 March 24, 2010 Version 2. February 4, 2010 Version 2. September 30, 2009 Version 2. September 1, 2009 Version 2. April 8, 2009. Solved In an effort to provide a quick and easy configuration guide for the Autodesk Network License Manager, I have decided to list the basic steps. Program Daily Vocal Exercise. First, we have recently implemented the evaluation of most transcendental functions inline, such as sin, cos, tan, and log, since there are x. However, as an example, if the argument to sin is the result of previous calculations performed on the floating point stack, then an 8. With our sin example, we have seen results even change sign due to the sin curve being so close to an x intercept value when evaluated. Consistency in this case can be maintained by calling a function which, due to the ABI, must push its arguments on the stack in this way memory is guaranteed to be accessed, even if the argument is an actual constant. Thus, even if the called function simply performs the inline expansion, using the function call as a wrapper to sin has the effect of trimming the argument precision down to the expected size. Using the Mnobuiltin option on the command line for C accomplishes this task by resolving all math routines in the library libm, thus performing a function call of necessity. Check The Lmgrd Log File' title='Check The Lmgrd Log File' />The other method of generating a function call for math routines, but one which may still produce the inline instructions, is by using the Kieee switch, described below. A second example which illustrates the precision control problem can be seen by examining this code fragment adapted from the benchmark paranoia, used to validate IEEE compliance. This section of code is used to determine machine precision. C. now w is just big enough that w1 w 1 1. In this case, where the variables are implicitly real, operations are performed on the floating point stack where optimization removed unneeded loads and stores from memory. Cst Check The Lmgrd Log File' title='Cst Check The Lmgrd Log File' />The general case of copy propagation being performed follows this pattern. Instead of storing x into a, then loading a to perform the addition, the value of x can be left on the floating point stack and have 2. Thus, memory accesses in some cases can be avoided, leaving answers in the extended real format. If copy propagation is disabled, stores of all left hand sides will automatically be performed, and reloaded when needed. This will have the effect of rounding any results to their declared sizes. For the above program, w has a value of 1. E1. 9 when executed as is extended precision. However, if Kieee is set, the value becomes 1. E0. 7 single precision. This difference is due to the fact that Kieee disables copy propagation, so all intermediate results are stored into memory, then reloaded when needed. Actually, copy propagation is only disabled for floating point operations, not integer,when the Kieee switch is set. Of course, with this particular example, setting the pc switch will also adjust the result. The switch Kieee also has the effect of making function calls to all transcendental routines. Although the routine still produces the machine instruction for computation unless in C the Mnobuiltin switch is set, arguments are passed on the stack, which results in a memory store and load. The final effect of the Kieee which we discuss is to disable reciprocal division for constant divisors. That is, for ab with unknown a and constant b, the expression is converted at compile time to a1b, thus turning an expensive divide into a relatively cheap multiplication. However, small discrepancies can again occur, resulting in differences from expected answers. Thus, understanding and correctly using the pc, Mnobuiltin, and Kieee switches should enable the user to produce the desired and expected precision for calculations which utilize floating point operations. The Desired Vendor Daemon Is Down Check The Lmgrd Log File' title='The Desired Vendor Daemon Is Down Check The Lmgrd Log File' />Note Current x. CPUs have SSE1,SSE2, SSE3, etc instruction sets which perform 3. This greatly reduces any precision discrepancies between x. CPU types. Why when I execute do I get the error message libpgc. The current Linux releases feature a shared libpgc. Before, the libraries libpgc. The default link will use a shared libpgc and libpghtread, so that users can build one executable for several versions of Linux. Building your application with, for example, pgcc on a RHEL 5. Su. SE 1. 1 3 system. Using gcc, however, the executable created should run on any Linux system with libc installed. We have done the same thing with libpgc. If you wish to execute code built on your for example Ubuntu 1. RHEL 6. 1 system, simply copy libpgc. PGIlinux. 86 6. REDIST to the target system, and add the directory you placed it in to the LDLIBRARYPATH path environment variable. As an example, if we build hello world on a RHEL 6. To run this program on platform B, which is Ubuntu 1. B yourBdirhi B. rcp PGIlinux. REDIST so B tmp. B export LDLIBRARYPATHLDLIBRARYPATH tmp. LDLIBRARYPATH indicates it is not defined, use. B export LDLIBRARYPATHtmp B. B yourBdirhi B. If libpgc. PGIlinux. LDLIBRARYPATH contents, if the shared library is present. Do you have any relative performance numbers While performance is a very important reason for using the PGI compilers, typically we do not publish any relative performance numbers. Performance depends upon too many factors to make a credible claim that we are N faster than a competitor. The only true measure is how your application performs on your system. Please download the PGI Community Edition and try it out. Two organizations that do publish performance results are Standard Performance Evaluation Corporation SPEC and Polyhedron. Polyhedron also allows you to download the benchmark source code so you can do your own performance comparison.