Berkeley TestFloat Release 3d: testfloat_ver

John R. Hauser
2017 August 18

Overview

The testfloat_ver program accepts test-case results obtained from exercising an implementation of floating-point arithmetic and verifies that those results conform to the IEEE Standard for Binary Floating-Point Arithmetic. testfloat_ver is part of the Berkeley TestFloat package, a small collection of programs for performing such tests. For general information about TestFloat, see file TestFloat-general.html.

A single execution of testfloat_ver verifies results for only a single floating-point operation and associated options. The testfloat_ver program must be repeatedly executed to verify results for each operation to be tested.

The test cases to be verified are read by testfloat_ver from standard input. This input will typically be piped from another program that, for each test case, invokes the floating-point operation and writes out the results. The format of testfloat_ver’s input is raw hexadecimal text, described in the section below titled Input Format.

For each test case given to it, testfloat_ver examines the computed results and reports any unexpected results as likely errors. For more about the operation of testfloat_ver and how to interpret its output, refer to TestFloat-general.html.

Command Syntax

The testfloat_ver program is executed as a command with this syntax:

testfloat_ver [<option>...] <function>
Square brackets ([ ]) denote optional arguments, <option> is a supported option, and <function> is the name of a testable operation. The available options are documented below. The testable operation names are listed in TestFloat-general.html. If testfloat_ver is executed without any arguments, a summary of usage is written.

Options

The testfloat_ver program accepts several command options. If mutually contradictory options are given, the last one has priority.

-help

The -help option causes a summary of program usage to be written, after which the program exits.

-errors <num>

The -errors option instructs testfloat_ver to report no more than the specified number of errors. The argument to -errors must be a nonnegative decimal integer. Once the specified number of error reports has been generated, the program exits. The default is -errors 20.

Against intuition, -errors 0 causes testfloat_ver to continue for any number of errors.

-checkNaNs

The -checkNaNs option causes testfloat_ver to verify the bitwise correctness of NaN results. In order for this option to be sensible, testfloat_ver must have been compiled so that its internal reference implementation of floating-point (Berkeley SoftFloat) generates the proper NaN results for the system being tested.

-precision32, -precision64, -precision80

When <function> is an 80-bit double-extended-precision operation affected by rounding precision control, the -precision32 option indicates that the rounding precision should be 32 bits, equivalent to 32-bit single-precision. Likewise, -precision64 indicates that the rounding precision should be 64 bits, equivalent to 64-bit double-precision, and -precision80 indicates that the rounding precision should be the full 80 bits of the double-extended-precision format. All these options are ignored for operations not affected by rounding precision control. When rounding precision is applicable but not specified, the default assumption is the full 80 bits, same as -precision80.

-rnear_even, -rnear_maxMag, -rminMag, -rmin, -rmax, -rodd

When <function> is an operation that requires rounding, the -rnear_even option indicates that rounding should be to nearest/even, -rnear_maxMag indicates rounding to nearest/maximum magnitude (nearest-away), -rminMag indicates rounding to minimum magnitude (toward zero), -rmin indicates rounding to minimum (down, toward negative infinity), -rmax indicates rounding to maximum (up, toward positive infinity), and -rodd, if supported, indicates rounding to odd. These options are ignored for operations that are exact and thus do not round. When rounding mode is relevant but not specified, the default assumption is rounding to nearest/even, same as -rnear_even.

-tininessbefore, -tininessafter

When <function> is an operation that requires rounding, the -tininessbefore option indicates that tininess on underflow should be detected before rounding, while -tininessafter indicates that tininess on underflow should be detected after rounding. These options are ignored for operations that are exact and thus do not round. When the method of tininess detection matters but is not specified, the default assumption is that tininess should be detected after rounding, same as -tininessafter.

-notexact, -exact

When <function> is an operation that rounds to an integer (either conversion to an integer type or a roundToInt operation), the -notexact option indicates that the inexact exception flag should never be raised, while -exact indicates that the inexact exception flag should be raised when the result is inexact. For other operations, these options are ignored. If neither option is specified, the default assumption is that the inexact exception flag should not be raised when rounding to an integer, same as -notexact.

Input Format

For a given <function> argument, the input format expected by testfloat_ver is the same as the output generated by program testfloat_gen for the same argument.

Input to testfloat_ver is expected to be text, with each line containing the data for one test case. The number of input lines thus equals the number of test cases. A single test case is organized as follows: first are the operands for the operation, next is the result value obtained, and last is a number indicating the exception flags that were raised. These values are all expected to be provided as raw hexadecimal numbers separated on the line by spaces. For example, for the command

testfloat_ver f64_add
valid input could include these lines:
3F90EB5825D6851E C3E0080080000000 C3E0080080000000 01
41E3C00000000000 C182024F8AE474A8 41E377F6C1D46E2D 01
7FD80FFFFFFFFFFF 7FEFFFFFFFFFFF80 7FF0000000000000 05
3FFFED6A25C534BE 3CA1000000020000 3FFFED6A25C534BF 01
...
On each line above, the first two hexadecimal numbers represent the 64-bit floating-point operands, the third hexadecimal number is the 64-bit floating-point result of the operation (the sum), and the last hexadecimal number gives the exception flags that were raised by the operation.

Note that, for floating-point values, the sign and exponent are at the most-significant end of the number. Thus, for the first number on the first line above, the leading hexadecimal digits 3F9 are the sign and encoded exponent of the 64-bit floating-point value, and the remaining digits are the encoded significand.

Exception flags are encoded with one bit per flag as follows:

bit 0    inexact exception
bit 1underflow exception
bit 2overflow exception
bit 3 infinite exception (“divide by zero”)
bit 4invalid exception