whetstone Whetstone FPU Benchmark

Overview

Whetstone is a classic synthetic benchmark program designed to evaluate processor arithmetic performance. By executing a series of standardized computational tasks, it provides accurate assessment of floating-point and integer operation capabilities.

This implementation is a C converted version of the Double Precision Whetstone benchmark, based on the work by Rich Painter (Painter Engineering, Inc.) from the netlib.org version.

The test results help developers:

  • Quantify FPU (Floating-Point Unit) performance

  • Analyze the impact of compiler optimization levels (-O2, -O3, etc.) on code execution efficiency

  • Compare arithmetic performance across different hardware platforms or system configurations

Configuration

Before running the test, enable the following Kconfig options:

# Enable custom permissive license components
CONFIG_ALLOW_CUSTOM_PERMISSIVE_COMPONENTS=y

# Enable Whetstone benchmark
CONFIG_BENCHMARK_WHETSTONE=y

# Whetstone requires floating-point support in the C library
CONFIG_LIBC_FLOATINGPOINT=y

Additional configuration options:

  • CONFIG_BENCHMARK_WHETSTONE_PROGNAME - Program name (default: “whetstone”)

  • CONFIG_BENCHMARK_WHETSTONE_PRIORITY - Task priority (default: 100)

  • CONFIG_BENCHMARK_WHETSTONE_STACKSIZE - Stack size (default: DEFAULT_TASK_STACKSIZE)

Usage

Command Syntax

whetstone [-c] [loops]

Parameters

  • [loops] - Module loop count. Sets the number of iterations for each internal test module. Increasing this value significantly increases computation and execution time. Default: 1000

  • -c - Continuous mode. When specified, the benchmark repeats indefinitely until interrupted. Default: disabled

Examples

Run a standard test with default parameters (1000 loops):

nsh> whetstone

Increase computation load per module (100000 loops):

nsh> whetstone 100000

Run in continuous mode with custom loop count:

nsh> whetstone -c 100000

Output Interpretation

After completion, whetstone outputs test configuration, total duration, and the final performance score.

Example Output

nsh> whetstone 100000

Loops: 100000, Iterations: 1, Duration: 5765 millisecond.
C Converted Double Precision Whetstones: 1.7 MIPS

  • Loops: 100000 - Each module executed 100,000 loop iterations

  • Iterations: 1 - The test suite ran 1 round

  • Duration: 5765 millisecond - Total execution time

  • 1.7 MIPS - Final performance score

Performance Metrics

MIPS / KIPS

  • Definition: Whetstone performance units - MIPS (Mega Whetstone Instructions Per Second) and KIPS (Kilo Whetstone Instructions Per Second)

  • Calculation: KIPS = (100.0 * loops * iterations) / (duration_sec * 1000)

  • Interpretation: Higher scores indicate better processor arithmetic performance

  • Unit conversion: Results display as KIPS when below 1000, otherwise as MIPS

Test Modules

The Whetstone benchmark consists of 11 carefully designed computational modules covering different operation types:

Module

Description

Module 1

Simple identifiers - basic floating-point operations

Module 2

Array elements - array-based floating-point operations

Module 3

Array as parameter - procedure calls with array arguments

Module 4

Conditional jumps - branch operations

Module 5

(Omitted)

Module 6

Integer arithmetic - complex integer operations

Module 7

Trigonometric functions - sin, cos, atan calculations

Module 8

Procedure calls - function call overhead

Module 9

Array references - array indexing operations

Module 10

Integer arithmetic - simple integer operations

Module 11

Standard functions - chained math functions (sqrt, exp, log)

Notes

  • This benchmark uses double-precision floating-point arithmetic

  • For accurate measurements, ensure the system is not under heavy load

  • If “Insufficient duration” is reported, increase the loop count

  • Timing precision is in milliseconds, enabling quick and accurate results even with fewer loop iterations on high-performance embedded CPUs

References