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287 lines
10 KiB
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<HTML>
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<TITLE>testfloat</TITLE>
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<BODY>
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<H1>Berkeley TestFloat Release 3e: <CODE>testfloat</CODE></H1>
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<P>
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John R. Hauser<BR>
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2018 January 20<BR>
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</P>
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<H2>Overview</H2>
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<P>
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The <CODE>testfloat</CODE> program tests an implementation of floating-point
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arithmetic for conformity to the IEEE Standard for Binary Floating-Point
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Arithmetic.
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<CODE>testfloat</CODE> is part of the Berkeley TestFloat package, a small
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collection of programs for performing such tests.
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For general information about TestFloat, see file
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<A HREF="TestFloat-general.html"><NOBR><CODE>TestFloat-general.html</CODE></NOBR></A>.
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</P>
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<P>
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The <CODE>testfloat</CODE> program is an all-in-one tool for testing
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floating-point arithmetic.
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It generates test operand values, invokes a floating-point operation with the
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generated operands, and examines the corresponding computed results, reporting
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unexpected results as likely errors.
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While the processes of generating inputs and examining results are generic, a
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particular build of <CODE>testfloat</CODE> is limited to testing only the one
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implementation of floating-point it has been compiled to invoke.
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For example, while one instance of <CODE>testfloat</CODE> might be compiled to
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execute a computer’s hardware instruction for floating-point addition, a
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different version might be compiled to call a subroutine called
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<CODE>myAddFloat</CODE> that is linked into the <CODE>testfloat</CODE> program.
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To test a new implementation of floating-point (a new set of machine
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instructions or a new set of subroutines), a new <CODE>testfloat</CODE> must be
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compiled containing the code needed to invoke the new floating-point.
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</P>
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<P>
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The default build of <CODE>testfloat</CODE> assumes that C types
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<CODE>float</CODE> and <CODE>double</CODE> are <NOBR>32-bit</NOBR> and
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<NOBR>64-bit</NOBR> binary floating-point types conforming to the IEEE
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Standard, and tests the C operations of <CODE>+</CODE>, <CODE>-</CODE>,
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<CODE>*</CODE>, <CODE>/</CODE>, type conversions, etc.
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This tests the floating-point arithmetic seen by C programs.
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Depending on the compiler and the options selected during compilation, this may
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or may not be the same as the computer’s floating-point hardware, if any.
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</P>
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<P>
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The <CODE>testfloat</CODE> program will ordinarily test an operation for all
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five rounding modes defined by the IEEE Floating-Point Standard, one after the
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other, plus possibly a sixth mode, <I>round to odd</I> (depending on the
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options selected when <CODE>testfloat</CODE> was compiled).
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If the rounding mode is not supposed to have any affect on the
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results—for instance, some operations do not require rounding—only
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the nearest/even rounding mode is checked.
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For double-extended-precision operations affected by rounding precision
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control, <CODE>testfloat</CODE> also tests all three rounding precision modes,
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one after the other.
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Testing can be limited to a single rounding mode and/or rounding precision with
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appropriate command-line options.
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</P>
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<P>
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For more about the operation of <CODE>testfloat</CODE> and how to interpret its
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output, refer to
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<A HREF="TestFloat-general.html"><NOBR><CODE>TestFloat-general.html</CODE></NOBR></A>.
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</P>
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<H2>Command Syntax</H2>
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<P>
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The <CODE>testfloat</CODE> program is executed as a command with this syntax:
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<BLOCKQUOTE>
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<PRE>
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testfloat [<<I>option</I>>...] <<I>function</I>>
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</PRE>
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</BLOCKQUOTE>
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Square brackets (<CODE>[ ]</CODE>) denote optional arguments,
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<CODE><<I>option</I>></CODE> is a supported option, and
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<CODE><<I>function</I>></CODE> is the name of either a testable operation
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or a function set.
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The available options and function sets are documented below.
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The <CODE>-list</CODE> option can be used to obtain a list of all testable
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operations for a given build of <CODE>testfloat</CODE>.
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If <CODE>testfloat</CODE> is executed without any arguments, a summary of usage
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is written.
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</P>
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<H2>Options</H2>
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<P>
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The <CODE>testfloat</CODE> program accepts several command options.
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If mutually contradictory options are given, the last one has priority.
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</P>
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<H3><CODE>-help</CODE></H3>
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<P>
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The <CODE>-help</CODE> option causes a summary of program usage to be written,
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after which the program exits.
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</P>
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<H3><CODE>-list</CODE></H3>
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<P>
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The <CODE>-list</CODE> option causes a list of testable operations to be
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written, after which the program exits.
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An operation is testable by <CODE>testfloat</CODE> if the program knows some
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way to invoke the operation.
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</P>
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<H3><CODE>-seed <<I>num</I>></CODE></H3>
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<P>
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The <CODE>-seed</CODE> option sets the seed for the pseudo-random number
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generator used for generating test cases.
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The argument to <CODE>-seed</CODE> is a nonnegative integer.
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Executing the same compiled <CODE>testfloat</CODE> program with the same
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arguments (including the same pseudo-random number seed) should always perform
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the same sequence of tests, whereas changing the pseudo-random number seed
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should result in a different sequence of tests.
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The default seed number <NOBR>is 1</NOBR>.
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</P>
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<H3><CODE>-level <<I>num</I>></CODE></H3>
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<P>
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The <CODE>-level</CODE> option sets the level of testing.
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The argument to <CODE>-level</CODE> can be either 1 <NOBR>or 2</NOBR>.
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The default is <NOBR>level 1</NOBR>.
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Level 2 performs many more tests than <NOBR>level 1</NOBR> and thus can reveal
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bugs not found by <NOBR>level 1</NOBR>.
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</P>
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<H3><CODE>-errors <<I>num</I>></CODE></H3>
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<P>
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The <CODE>-errors</CODE> option instructs <CODE>testfloat</CODE> to report no
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more than the specified number of errors for any combination of operation,
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rounding mode, etc.
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The argument to <CODE>-errors</CODE> must be a nonnegative decimal integer.
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Once the specified number of error reports has been generated,
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<CODE>testfloat</CODE> ends the current test and begins the next one, if any.
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The default is <NOBR><CODE>-errors</CODE> <CODE>20</CODE></NOBR>.
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</P>
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<P>
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Against intuition, <NOBR><CODE>-errors</CODE> <CODE>0</CODE></NOBR> causes
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<CODE>testfloat</CODE> to report every error it finds.
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</P>
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<H3><CODE>-errorstop</CODE></H3>
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<P>
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The <CODE>-errorstop</CODE> option causes the program to exit after the first
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operation for which any errors are reported.
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</P>
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<H3><CODE>-forever</CODE></H3>
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<P>
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The <CODE>-forever</CODE> option causes a single operation to be repeatedly
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tested.
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Only one rounding mode and/or rounding precision can be tested in a single
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execution.
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If not specified, the rounding mode defaults to nearest/even.
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For <NOBR>80-bit</NOBR> double-extended-precision operations, the rounding
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precision defaults to full double-extended precision.
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The testing level is set to 2 by this option.
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</P>
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<H3><CODE>-checkNaNs</CODE></H3>
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<P>
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The <CODE>-checkNaNs</CODE> option causes <CODE>testfloat</CODE> to verify the
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bitwise correctness of NaN results.
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In order for this option to be sensible, <CODE>testfloat</CODE> must have been
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compiled so that its internal reference implementation of floating-point
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(Berkeley SoftFloat) generates the proper NaN results for the system being
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tested.
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</P>
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<H3><CODE>-checkInvInts</CODE></H3>
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<P>
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The <CODE>-checkInvInts</CODE> option causes <CODE>testfloat</CODE> to verify
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the bitwise correctness of integer results of invalid operations.
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In order for this option to be sensible, <CODE>testfloat</CODE> must have been
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compiled so that its internal reference implementation of floating-point
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(Berkeley SoftFloat) generates the proper integer results for the system being
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tested.
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</P>
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<H3><CODE>-checkAll</CODE></H3>
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<P>
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Enables both <CODE>-checkNaNs</CODE> and <CODE>-checkInvInts</CODE>.
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</P>
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<H3><CODE>-precision32, -precision64, -precision80</CODE></H3>
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<P>
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For <NOBR>80-bit</NOBR> double-extended-precision operations affected by
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rounding precision control, the <CODE>-precision32</CODE> option restricts
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testing to only the cases in which the rounding precision is
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<NOBR>32 bits</NOBR>, equivalent to <NOBR>32-bit</NOBR> single-precision.
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The other rounding precision choices are not tested.
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Likewise, <CODE>-precision64</CODE> fixes the rounding precision to
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<NOBR>64 bits</NOBR>, equivalent to <NOBR>64-bit</NOBR> double-precision, and
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<CODE>-precision80</CODE> fixes the rounding precision to the full
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<NOBR>80 bits</NOBR> of the double-extended-precision format.
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All these options are ignored for operations not affected by rounding precision
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control.
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</P>
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<P>
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The precision-control options may not be supported at all if no
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double-extended-precision operations are testable.
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</P>
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<H3><CODE>-rnear_even, -rnear_maxMag, -rminMag, -rmin, -rmax, -rodd</CODE></H3>
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<P>
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The <CODE>-rnear_even</CODE> option restricts testing to only the cases in
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which the rounding mode is nearest/even.
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The other rounding mode choices are not tested.
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Likewise, <CODE>-rnear_maxMag</CODE> forces rounding to nearest/maximum
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magnitude (nearest-away), <CODE>-rminMag</CODE> forces rounding to minimum
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magnitude (toward zero), <CODE>-rmin</CODE> forces rounding to minimum (down,
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toward negative infinity), <CODE>-rmax</CODE> forces rounding to maximum (up,
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toward positive infinity), and <CODE>-rodd</CODE>, if supported, forces
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rounding to odd.
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These options are ignored for operations that are exact and thus do not round,
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or that have the rounding mode included in the function name (such as
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<CODE>f32_to_i32_r_near_maxMag</CODE>).
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</P>
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<H3><CODE>-tininessbefore, -tininessafter</CODE></H3>
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<P>
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The <CODE>-tininessbefore</CODE> option indicates that the floating-point
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implementation being tested detects tininess on underflow before rounding.
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The <CODE>-tininessafter</CODE> option indicates that tininess is detected
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after rounding.
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The <CODE>testfloat</CODE> program alters its expectations accordingly.
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These options override the default selected when <CODE>testfloat</CODE> was
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compiled.
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Choosing the wrong one of these two options should cause error reports for some
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(but not all) operations.
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</P>
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<H2>Function Sets</H2>
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<P>
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Just as <CODE>testfloat</CODE> can test an operation for all five or six
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rounding modes in sequence, multiple operations can be tested with a single
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execution of <CODE>testfloat</CODE>.
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Two sets are recognized: <CODE>-all1</CODE> and <CODE>-all2</CODE>.
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The set <CODE>-all1</CODE> is all one-operand operations, while
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<CODE>-all2</CODE> is all two-operand operations.
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A function set is used in place of an operation name in the
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<CODE>testfloat</CODE> command line, such as
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<BLOCKQUOTE>
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<PRE>
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testfloat [<<I>option</I>>...] -all1
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</PRE>
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</BLOCKQUOTE>
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</P>
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</BODY>
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