roundingFunction

Parameter	Description
input ports	1 input port(s) declared.

Parameter	Description
output ports	1 output port(s) declared.

📄Description

Rounds the input to an integer value.

Module	`nflow_blocks`
Library	Math blocks
Type	`roundingFunction`
Label	Rounding Function

Description

Applies the rounding mode selected by the Operator parameter, element-wise, with scalar expansion for vector signals.

Operator

floor: round toward minus infinity.

ceil: round toward plus infinity.

round: round to the nearest integer, ties away from zero.

fix: truncate toward zero.

This page describes the native runtime behavior observed in the module C++ sources. Declared phases indicate when the simulation engine calls the block.

Code generation: supported for C and Rust.

Implementation Sources

Manifestmodules/nflow_blocks/libraries/math/library.json

{
  "id": "builtin.math",
  "title": "Math",
  "version": "1.0.0",
  "format": "nflow-2",
  "metadata": {
    "author": "Allan CORNET",
    "created": "2026-03-21",
    "tool": "Nelson nflow"
  },
  "builtin": true,
  "comment": "Basic math blocks",
  "license": "LGPL-3.0",
  "blocks": [
    {
      "type": "matmul",
      "label": "MatMul",
      "icon": "matmul.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 60,
      "height": 60,
      "inputs": [
        {
          "x": 0,
          "y": 20,
          "side": "left"
        },
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 60,
          "y": 30,
          "side": "right"
        }
      ],
      "defaultParams": {
        "MultiplicationRule": "matrix"
      }
    },
    {
      "type": "sumElements",
      "label": "Sum of Elements",
      "icon": "sumElements.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {},
      "render": {
        "type": "image",
        "src": "exports/sumElements.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "productOfElements",
      "label": "Product of Elements",
      "icon": "productOfElements.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {},
      "render": {
        "type": "image",
        "src": "exports/productOfElements.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "dotProduct",
      "label": "Dot Product",
      "icon": "dotProduct.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 30,
          "side": "left"
        },
        {
          "x": 0,
          "y": 50,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {},
      "render": {
        "type": "image",
        "src": "exports/dotProduct.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "crossProduct",
      "label": "Cross Product",
      "icon": "crossProduct.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 30,
          "side": "left"
        },
        {
          "x": 0,
          "y": 50,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {},
      "render": {
        "type": "image",
        "src": "exports/crossProduct.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "gain",
      "label": "Gain",
      "icon": "gain.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 100,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 100,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {
        "Gain": 2
      },
      "render": {
        "type": "math",
        "formula": "{params.Gain}",
        "mathGroupClass": "gain-math",
        "textSize": "16px",
        "width": 100,
        "height": 80
      }
    },
    {
      "type": "sum",
      "label": "Sum",
      "icon": "sum.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 20,
      "height": 20,
      "inputs": [
        {
          "x": -30,
          "y": 10,
          "side": "left",
          "wireX": -10,
          "wireY": 10
        },
        {
          "x": 10,
          "y": -30,
          "side": "top",
          "wireX": 10,
          "wireY": -10
        },
        {
          "x": 10,
          "y": 50,
          "side": "bottom",
          "wireX": 10,
          "wireY": 30
        }
      ],
      "outputs": [
        {
          "x": 50,
          "y": 10,
          "side": "right",
          "wireX": 30,
          "wireY": 10
        }
      ],
      "defaultParams": {
        "Inputs": "+++"
      },
      "render": {
        "type": "math",
        "formula": "\\oplus",
        "mathGroupClass": "sum-math",
        "textSize": "16px",
        "width": 20,
        "height": 20
      }
    },
    {
      "type": "mult",
      "label": "Mult",
      "icon": "mult.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 20,
      "height": 20,
      "inputs": [
        {
          "x": -30,
          "y": 10,
          "side": "left",
          "wireX": -10,
          "wireY": 10
        },
        {
          "x": 10,
          "y": -30,
          "side": "top",
          "wireX": 10,
          "wireY": -10
        },
        {
          "x": 10,
          "y": 50,
          "side": "bottom",
          "wireX": 10,
          "wireY": 30
        }
      ],
      "outputs": [
        {
          "x": 50,
          "y": 10,
          "side": "right",
          "wireX": 30,
          "wireY": 10
        }
      ],
      "defaultParams": {},
      "render": {
        "type": "math",
        "formula": "\\otimes",
        "mathGroupClass": "mult-math",
        "textSize": "16px",
        "width": 20,
        "height": 20
      }
    },
    {
      "type": "abs",
      "label": "Abs",
      "icon": "abs.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {},
      "render": {
        "type": "math",
        "formula": "|x|",
        "mathGroupClass": "abs-math",
        "textSize": "16px",
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "mathFunction",
      "label": "Math Function",
      "icon": "mathFunction.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {
        "Function": "exp"
      },
      "render": {
        "type": "image",
        "src": "exports/mathFunction.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "trigFunction",
      "label": "Trigonometric Function",
      "icon": "trigFunction.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {
        "Function": "sin"
      },
      "render": {
        "type": "image",
        "src": "exports/trigFunction.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "roundingFunction",
      "label": "Rounding Function",
      "icon": "roundingFunction.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {
        "Operator": "floor"
      },
      "render": {
        "type": "image",
        "src": "exports/roundingFunction.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "sign",
      "label": "Sign",
      "icon": "sign.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {},
      "render": {
        "type": "image",
        "src": "exports/sign.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "sqrt",
      "label": "Sqrt",
      "icon": "sqrt.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {
        "Function": "sqrt"
      },
      "render": {
        "type": "image",
        "src": "exports/sqrt.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "divide",
      "label": "Divide",
      "icon": "divide.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 30,
          "side": "left"
        },
        {
          "x": 0,
          "y": 50,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {},
      "render": {
        "type": "image",
        "src": "exports/divide.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "negate",
      "label": "Negate",
      "icon": "negate.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {},
      "render": {
        "type": "image",
        "src": "exports/negate.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "bias",
      "label": "Bias",
      "icon": "bias.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {
        "Bias": 1
      },
      "render": {
        "type": "image",
        "src": "exports/bias.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "min",
      "label": "Min",
      "icon": "min.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 30,
          "side": "left"
        },
        {
          "x": 0,
          "y": 50,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {},
      "render": {
        "type": "math",
        "formula": "min(x,y)",
        "mathGroupClass": "min-math",
        "textSize": "16px",
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "max",
      "label": "Max",
      "icon": "max.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 30,
          "side": "left"
        },
        {
          "x": 0,
          "y": 50,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {},
      "render": {
        "type": "math",
        "formula": "max(x,y)",
        "mathGroupClass": "max-math",
        "textSize": "16px",
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "realImagToComplex",
      "label": "Re-Im to Complex",
      "icon": "realImagToComplex.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 60,
      "height": 60,
      "inputs": [
        {
          "x": 0,
          "y": 20,
          "side": "left"
        },
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 60,
          "y": 30,
          "side": "right"
        }
      ],
      "defaultParams": {}
    },
    {
      "type": "complexToRealImag",
      "label": "Complex to Re-Im",
      "icon": "complexToRealImag.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 60,
      "height": 60,
      "inputs": [
        {
          "x": 0,
          "y": 30,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 60,
          "y": 20,
          "side": "right"
        },
        {
          "x": 60,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {}
    },
    {
      "type": "magnitudeAngleToComplex",
      "label": "Mag-Angle to Complex",
      "icon": "magnitudeAngleToComplex.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 60,
      "height": 60,
      "inputs": [
        {
          "x": 0,
          "y": 20,
          "side": "left"
        },
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 60,
          "y": 30,
          "side": "right"
        }
      ],
      "defaultParams": {}
    },
    {
      "type": "complexToMagnitudeAngle",
      "label": "Complex to Mag-Angle",
      "icon": "complexToMagnitudeAngle.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 60,
      "height": 60,
      "inputs": [
        {
          "x": 0,
          "y": 30,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 60,
          "y": 20,
          "side": "right"
        },
        {
          "x": 60,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {}
    },
    {
      "type": "conjugate",
      "label": "Conjugate",
      "icon": "conjugate.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 60,
      "height": 60,
      "inputs": [
        {
          "x": 0,
          "y": 30,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 60,
          "y": 30,
          "side": "right"
        }
      ],
      "defaultParams": {}
    },
    {
      "type": "atan2",
      "label": "Atan2",
      "icon": "atan2.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 60,
      "height": 60,
      "inputs": [
        {
          "x": 0,
          "y": 20,
          "side": "left"
        },
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 60,
          "y": 30,
          "side": "right"
        }
      ],
      "defaultParams": {}
    },
    {
      "type": "wrapToZero",
      "label": "Wrap To Zero",
      "icon": "wrapToZero.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {
        "Threshold": 255
      },
      "render": {
        "type": "image",
        "src": "exports/wrapToZero.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    },
    {
      "type": "polynomial",
      "label": "Polynomial",
      "icon": "polynomial.svg",
      "phases": [
        "ALGEBRAIC"
      ],
      "width": 80,
      "height": 80,
      "inputs": [
        {
          "x": 0,
          "y": 40,
          "side": "left"
        }
      ],
      "outputs": [
        {
          "x": 80,
          "y": 40,
          "side": "right"
        }
      ],
      "defaultParams": {
        "Coefficients": [
          1,
          0,
          0
        ]
      },
      "render": {
        "type": "image",
        "src": "exports/polynomial.svg",
        "svgMode": "element",
        "preserveAspectRatio": "none",
        "x": 0,
        "y": 0,
        "width": 80,
        "height": 80
      }
    }
  ]
}

Runtimemodules/nflow_blocks/src/cpp/math/roundingFunction.cpp

//=============================================================================
// Copyright (c) 2016-present Allan CORNET (Nelson)
//=============================================================================
// This file is part of Nelson.
//=============================================================================
// LICENCE_BLOCK_BEGIN
// SPDX-License-Identifier: LGPL-3.0-or-later
// LICENCE_BLOCK_END
//=============================================================================
// roundingFunction: element-wise rounding block whose params.Operator selects
// the rounding mode (floor/ceil/round/fix). Feedthrough (ALGEBRAIC), real
// double signals, vector element-wise; has C / Rust code generation.
//   floor -> toward -inf     ceil -> toward +inf
//   round -> nearest, ties away from zero     fix -> truncate toward zero
//=============================================================================
#include "SimEngineTypes.hpp"
#include "BlockRegistry.hpp"
#include "FieldNames.hpp"
#include "NFlowBlockDescriptor.hpp"
#include "math_blocks.hpp"
#include <cmath>
#include <string>
//=============================================================================
namespace Nelson {
namespace NFlow {
    //=============================================================================
    namespace {
        double
        applyRounding(const std::string& op, double x)
        {
            if (op == "ceil") {
                return std::ceil(x);
            }
            if (op == "round") {
                return std::round(x); // ties away from zero
            }
            if (op == "fix") {
                return std::trunc(x); // toward zero
            }
            return std::floor(x); // "floor" (default)
        }

        // C / Rust intrinsic name for the selected operator.
        std::string
        roundingFn(const std::string& op, bool rust)
        {
            const std::string p = rust ? "libm::" : "";
            if (op == "ceil") {
                return p + "ceil";
            }
            if (op == "round") {
                return p + "round";
            }
            if (op == "fix") {
                return p + "trunc";
            }
            return p + "floor";
        }

        BlockCodegenTemplate
        makeCodegen(bool rust)
        {
            BlockCodegenTemplate t;
            t.emitStep = [rust](const BlockCodegenArgs& a) {
                nflow::BlockDescriptor bd(*a.block, *a.variables);
                const std::string op = bd.paramStr("Operator", "floor");
                a.line("out_" + a.id + " = " + roundingFn(op, rust) + "(" + a.in[0] + ");");
            };
            return t;
        }
    } // namespace
    //=============================================================================
    bool
    handleRoundingFunction(SimCtx& ctx, const Block& b, Phase phase)
    {
        if (phase != Phase::ALGEBRAIC) {
            return false;
        }
        if (!hasInput(ctx, b.nid, 0)) {
            return false;
        }
        nflow::BlockDescriptor bd(b, ctx.variables);
        const std::string op = bd.paramStr("Operator", "floor");
        SigView u = getInputSig(ctx, b.nid, 0);
        return emitElementwise(ctx, b.nid, [&](int i) { return applyRounding(op, sigAt(u, i)); });
    }
    //=============================================================================
    BlockCodegenTemplate
    getCodeGenCRoundingFunction()
    {
        return makeCodegen(false);
    }
    //=============================================================================
    BlockCodegenTemplate
    getCodeGenRustRoundingFunction()
    {
        return makeCodegen(true);
    }
    //=============================================================================
} // namespace NFlow
} // namespace Nelson
//=============================================================================