rack vs simd on monophonic synth

Development
1

is there any benefits of using rack simd tools for monophonic synth?

ive controls for a 4xosc, but can’t param[].getValue using simd, neither inputs[].

its seems suitable only for poly/voices. correct? or can i benefit simd also for mono?

example: get freq 1/2/3/4 from param once, pitch 1/2/3/4 once and do freq4 * pitch4. the same for inputs…

this way also mono synth can benefit simd :slight_smile:

2

You can initialize float_4’s from single floats easily (the same value is copied for all the elements of the SIMD vector) :

        simd::float_4 parvalsimd = params[PAR_BAL_ATTN].getValue();

        simd::float_4 inportsimd = inputs[IN_BALANCE].getVoltage();
3

thats not what i need for improve processing by simd (param/inputs). on your example, on parvalsimd it should store PAR_BAL_ATTN + 0, PAR_BAL_ATTN + 1, PAR_BAL_ATTN + 2 and PAR_BAL_ATTN + 3 (i.e. all PAR_BAL_ATTN for each osc).

reading “once” from memory :slight_smile: the same as for getPolyVoltage() from inputs (the reason why it exist in fact).

4 
simd::float_4 parvals_simd{params[PAR_1].getValue(),params[PAR_2].getValue(),params[PAR_3].getValue(),params[PAR_4].getValue()};

So, kind of annoying to write, but you could write some little function that does all that.

5

of course dude :slight_smile: but thats not taking advantage of simd/cache/pipeline and so.

as i said, the same reason why getPolyVoltage exist.

basically, with your code it does 4 memory read instead of a single one (roughly).

6

You just need to take that performance hit in this case for the initialization of the SIMD vector. That doesn’t affect how the subsequent SIMD operations work.

7

My SN-101 smooth noise oscillator is monophonic, but it uses simd for the noise algorithm, and actually for the random number generator as well.

8

of course. still not very “good” at performance, when you have lots of param/inputs to process. example:

simd::float_4 fillParam(ParamIds paramId) {
    return {params[paramId + 0].getValue(), params[paramId + 1].getValue(), params[paramId + 2].getValue(), params[paramId + 3].getValue()};
}
simd::float_4 fillInput(InputIds inputId, int voiceIndex) {
    return {inputs[inputId + 0].getVoltage(voiceIndex), inputs[inputId + 1].getVoltage(voiceIndex), inputs[inputId + 2].getVoltage(voiceIndex), inputs[inputId + 3].getVoltage(voiceIndex)};
}
simd::float_4 fillInputIsConnected(InputIds inputId) {
    return {(float)inputs[inputId + 0].isConnected(), (float)inputs[inputId + 1].isConnected(), (float)inputs[inputId + 2].isConnected(), (float)inputs[inputId + 3].isConnected()};
}

//

const rack::simd::float_4 paramPhase = fillParam(PHASE_PARAM);
const rack::simd::float_4 paramFreqOffset = fillParam(FREQ_OFFSET_PARAM);
const rack::simd::float_4 paramPitch = fillParam(PITCH_PARAM) / 1200.0f;
const rack::simd::float_4 paramNoiseMix = fillParam(NOISE_MIX_PARAM);
const rack::simd::float_4 paramNoiseTone = fillParam(NOISE_TONE_PARAM);
const rack::simd::float_4 paramVol = fillParam(VOL_PARAM);
const rack::simd::float_4 paramOut = (fillParam(OUT_PARAM) - 0.5f) * 2.0f;
const rack::simd::float_4 paramPan = fillParam(PAN_PARAM);
const rack::simd::float_4 inputVolIsConnected = fillInputIsConnected(VOL_INPUT);
const rack::simd::float_4 inputOutIsConnected = fillInputIsConnected(OUT_INPUT);