Block type: gain
| Parameter | Description |
|---|---|
| input ports | 1 input port(s) declared. |
| Parameter | Description |
|---|---|
| output ports | 1 output port(s) declared. |
Multiplies the input by a scalar gain.
| Module |
nflow_blocks
|
| Library | Math blocks |
| Type |
gain
|
| Label | Gain |
Description
Simple multiplicative gain block. Multiplies the input by a constant gain.
Ports
Input(s)
| Port | Role | Side | Position |
|---|---|---|---|
| Port_1 | Numeric signal read by the block. | left | x=0, y=40 |
Output(s)
| Port | Role | Side | Position |
|---|---|---|---|
| Port_1 | Numeric signal produced by the block. | right | x=100, y=40 |
Parameters
| Parameter | Default value |
|---|---|
gain
|
2 |
Inspector Keys
These serialized keys are exposed by the block inspector.
gain
Block Characteristics
| Block type | gain |
| Family | Math blocks |
| Rendered size | 100 x 80 |
| Phases | ALGEBRAIC |
| Direct feedthrough | yes |
| Internal state or history | yes |
| Signal data type | double numeric values |
Algorithms
Equation or Rule
$$y = gain\,u$$Extended Capabilities
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
modules/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
}
}
]
}
modules/nflow_blocks/src/cpp/math/gain.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
//=============================================================================
#include "SimEngineTypes.hpp"
#include "BlockRegistry.hpp"
#include "FieldNames.hpp"
#include "NFlowBlockDescriptor.hpp"
#include "NFlowCodegenTyped.hpp"
#include "math_blocks.hpp"
#include <cmath>
#include <algorithm>
//=============================================================================
bool
Nelson::NFlow::handleGain(SimCtx& ctx, const Block& b, Phase phase)
{
if (phase != Phase::ALGEBRAIC) {
return false;
}
if (!hasInput(ctx, b.nid, 0)) {
// Disconnected: hold previous output
setOutput(ctx, b.nid, ctx.blockState[b.nid].output);
return false;
}
nflow::BlockDescriptor bd(b, ctx.variables);
double gainVal = bd.paramDouble(nflow::kGain, 1.0);
SigView u = getInputSig(ctx, b.nid, 0);
if (const PortSig* ps = exact64OutPort(ctx, b.nid)) {
const SigType ty = ps->type;
const bool sat = blockSaturates(ctx, b.nid);
const long long k = quantizeDoubleToI64(gainVal, ty);
return emitElementwiseI64(
ctx, b.nid, [&](int i) { return i64ApplyMul(sigAtI64(u, i, ty), k, ty, sat); });
}
if (complexOutPort(ctx, b.nid)) {
return emitElementwiseComplex(ctx, b.nid, [&](int i) { return sigAtC(u, i) * gainVal; });
}
return emitElementwise(ctx, b.nid, [&](int i) { return sigAt(u, i) * gainVal; });
}
//=============================================================================
namespace {
Nelson::NFlow::BlockCodegenEmitFn
gainTypedEmitter(bool cLang, double dflt)
{
using namespace Nelson::NFlow;
return [cLang, dflt](const BlockCodegenArgs& a) {
nflow::BlockDescriptor bd(*a.block, *a.variables);
const bool uns = codegenIsU64(a.outType);
const bool sat = codegenSaturates(a);
const long long k = quantizeDoubleToI64(
bd.paramDouble(nflow::kGain, dflt), uns ? SigType::UInt64 : SigType::Int64);
a.line("out_" + a.id + " = "
+ codegenI64BinOp("mul", a.in[0], codegenI64Literal(k, uns, cLang), uns, sat, cLang)
+ ";");
};
}
} // namespace
//=============================================================================
Nelson::NFlow::BlockCodegenTemplate
Nelson::NFlow::getCodeGenCGain()
{
BlockCodegenTemplate t;
// Absent Gain defaults to 1.0 (unity passthrough), matching the interpreter
// (handleGain) and the Rust backend. A 0.0 default zeroed the output of any
// gain block whose Gain param was unset.
t.step = "out_{id} = {in0} * {param:Gain:1.0};";
t.emitStepTyped = gainTypedEmitter(true, 1.0);
return t;
}
//=============================================================================
Nelson::NFlow::BlockCodegenTemplate
Nelson::NFlow::getCodeGenRustGain()
{
BlockCodegenTemplate t;
t.step = "out_{id} = {param:Gain:1.0} * {in0};";
t.emitStepTyped = gainTypedEmitter(false, 1.0);
return t;
}
//=============================================================================
| Version | Description |
|---|---|
| 1.0.0 | initial version |